Flower(Latin flos, Greek anthos) is the reproductive organ of angiosperms. The main role of the flower is that it completely combines all the processes of asexual and sexual reproduction. Most botanists use the following definition:
flower – this is a modified, shortened, limited in growth, unbranched spore-bearing shoot, intended for the formation of spores, gametes and the sexual process, culminating in the formation of seeds and fruit.
A flower is a unique formation in its nature and functions; it is also diverse in structural details, color and size. Tiny flowers are known - about 1 mm in diameter (Duckweed family), and at the same time there are giant flowers, like Arnold's rafflesia (Rafflesia arnoldii). The flower of this plant (Kalimantan island) reaches 1 m in diameter and is the largest among angiosperms.
The flower arises from the growth cone of the flower shoot. Tepals, stamens and pistils are sequentially laid down in the form of tubercles of the apical meristem. Initially, the processes of formation and development of floral structures are carried out in the flower bud. A flower bud usually consists of a bud cover (perula), formed by bud scales that tightly surround the young flower, or bud. Sometimes there is no cover and the bud is protected by young leaves that tightly fit individual flowers or entire inflorescences.
According to the position of the flowers there are apical or lateral. In a lateral position, the flower emerges from the axil of a modified or unmodified bract (bract).
The morphological parts of the flower have stem and leaf origin. The stem part of the flower is represented by the peduncle and receptacle, the leaf part is the perianth, stamens and pistils.
Peduncle- this is the area of the shoot between the flower and the bract. If the peduncle is shortened or absent, the flower is called sedentary , (plantain, clover) (Fig. 1).
Receptacle- this is the upper expanded part of the peduncle to which all parts of the flower are attached. It can have different shapes: flat (peony), conical (buttercup), elongated (magnolia, strawberry), concave (rose, cherry).
Rice. 1. Flower structure diagram:
1 – stigma; 2 – ovary; 3 – column; 4 – ovule; 5 – filament;
6 – liaison officer; 7 – anther; 8 – anther in section; 9 – pollen grains;
10 – petal; 11 – sepal; 12 – receptacle; 13 – peduncle;
14 – bract; 15 – bract
Some flowers have a hypanthium. Hypantium - This is a special goblet-shaped structure that is formed as a result of the fusion of the receptacle, the lower parts of the perianth and the stamen filaments. It is characteristic of representatives of the Rosaceae family and some species of legumes. In some plants, the hypanthium participates in the formation of the fruit (rose hips).
On the receptacle, all parts of the flower can be located as follows:
A) in circles, or whorls (cyclic flower);
b) in a spiral(acyclic flower) - in such flowers the number of each part is usually indefinite;
V) semi-whorled(hemicyclic flower) - the circular arrangement of some parts of the flower is combined with the spiral arrangement of others.
Most plants are characterized by four-circular and five-circular cyclic flowers. For example, in cloves, the sepals are located in one circle, the petals are in one, the stamens are in one or two, the pistils are in one circle (4–5 circles in total).
The parts of a flower are usually divided into two groups:
1) sterile– perianth;
2) reproductive (fertile)– stamens, pistil(s).
Perianth – this is the sterile part of the flower, which consists of a calyx and corolla. There are two types of perianths:
1) double – consists of a calyx and a corolla (pea);
2) simple – consists of a set of homogeneous leaves (not differentiated into a calyx and corolla). A simple perianth can be cup-shaped, consisting of green leaves (beets, sorrel) and corolla-shaped having brightly colored leaves (tulip, buckwheat).
There are also flowers in which the perianth is reduced and presented in the form bristles(reed) or hairs(cotton grass) or it is absent (willow, poplar). A flower that does not have a perianth is called naked or coverless. The reduction of the perianth is associated with adaptation to wind pollination.
Cup comprises sepals, most often colored green, which form the outer circle of the perianth. The number of sepals in a flower varies from two (poppy family) to an indefinite number (tea family); in most dicotyledons there are usually four or five.
Most often, the calyx consists of one circle of sepals, but sometimes a second circle is formed. He is called subordinate (mallow, pink). The leaves of the subcup are homologous to the stipules. The calyx arose as a result of modification of the upper bract leaves.
The main function of the calyx is to protect the internal parts of the flower until the bud opens (drying, low temperatures). When a flower opens or during flowering, the calyx sometimes falls off (Poppy family) or bends back and becomes inconspicuous. However, it often changes, acquiring new functions that are associated with the distribution of fruits and seeds. In the Lamiaceae family, the calyx serves as a container for the fractional fruit; in asteraceae it is transformed into a pappus (pappus), which facilitates the distribution of fruits by the wind. The string develops hooks on the calyx, which are preserved during the fruiting process. With the help of hooks, the fruits cling to the fur of animals.
Sometimes the calyx is brightly colored (monkshood, fuchsia, sokirk) and performs or enhances the function of the corolla in attracting pollinating insects. In this case, the corolla is often reduced to nectaries (hellebore, larkspur). In some cases, the calyx is poorly developed (celery, valerian).
There are two types of cups:
1) free-leaved (lobed) – all sepals are free, unfused (cabbage, buttercup);
2) plexifolia (spinophyllate) - sepals partially or completely fused together. In such a calyx, a tube, teeth, or lobes, and lobes are distinguished depending on the degree of fusion of the sepals, the number of which corresponds to the number of sepals. Based on the shape of the tube, there are tubular (Kalanchoe trumpetiflora), bell-shaped (white lily) and funnel-shaped (Raphiolepsis umbelliferous) calyxes. In some lamiaceae (scutellaria, beangrass), the calyx is called bilabial, since it is divided into two unequal parts, each of which is called a lip.
whisk consists of petals and forms the inner part of a double perianth. In the process of evolution, petals evolved from stamens that lost their anthers. The number of petals can be indefinite, but is usually four, five or three. The corolla determines the appearance of the flower. It promotes its pollination by attracting pollinating insects with its color, size or characteristic shape. Thanks to the bright color of the petals, it is able to reflect part of the spectrum of sunlight, thereby protecting the reproductive parts of the flower from overheating. By closing at night, the corolla, on the contrary, creates a chamber that prevents excessive cooling of the flower or damage to it by cold dew. In some cases, the corolla is completely reduced, and then its functions are transferred to the calyx.
The color of the corolla petals is determined by various pigments: anthocyanin (pink, red, blue, purple), carotenoids (yellow, orange, red), anthochlor (lemon yellow), antopheine (brown). The white color is due to the absence of any pigments and the reflection of light rays.
The aroma of flowers is created by volatile substances, mainly essential oils, which are formed in the epidermal cells of the petals and perianth leaves, and in some plants - in osmophores (various shaped glands with secretory tissue). The released essential oils usually evaporate immediately.
There are two types of rims (Fig. 2):
1) free-petalled (separate) - all petals are free, unfused. The oldest living angiosperms (Magnoliaceae, Ranunculaceae, Nymphaeaceae) are free-petalled. In representatives of more developed families (legumes, cloves), two parts are distinguished in the petal: a) marigold– lower narrowed part; b) plate (bend)– the upper expanded part, which is located at right angles to the nail;
2) interpetalous (spinopetalous) - petals partially or completely fused together. Composite corollas are characteristic, as a rule, of insect-pollinated plants. They distinguish three morphological parts: a) a tube– lower fused part; b) bend– upper extended part; V) pharynx– the place of transition of the tube into the bend. In the pharynx there are sometimes various kinds of outgrowths and appendages in the form of scales, denticles, ridges (borage, clove, gentian). They prevent water and unwanted insects from entering the base of the tube. The length of the tube varies and reflects the characteristics of the pollination mechanism. The increase in the length of the tube (up to 20–25 cm in tropical species of Datura) is associated with adaptation to pollination by long-proboscis butterflies and birds.
The petals of the corolla are either more or less the same (buttercup, raspberry, apple tree), or differ in size and shape (legume, violet). This should also include the formation of hollow outgrowths at the petals - Spurs(larkspur, aconite, toadflax, snapdragon), associated with the characteristics of pollination. Nectar accumulates in the cavity of the spur, which is secreted by its wall or special nectaries.
Rice. 2. Modifications of petals (examples):
A– marigold petal (coronaria cuckoo flower); B– sessile petal with a nectar pit at the base (acidic buttercup); IN– a sessile petal with a cylindrical spur at the base (Red fingerhorn); 1 – marigold; 2 – bend; 3 – appendage (coronal lobes); 4 – scale covering the nectar pit; 5 – cylindrical spur; 6 – entrance to the spur
Nectar accumulates in the cavity of the spur, which is secreted by its wall or special nectaries.
In some cases (grape, myrtle) petals can grow together at the tops, remaining free at the base. When a flower blooms, such a perianth often falls off in the form of a cap (calyptra). In such plants, insects are attracted to numerous brightly colored stamens.
One of the characteristic features of the perianth is symmetry . Based on this characteristic, flowers are divided into three morphological groups (Fig. 3):
1) actinomorphic (regular) – two or more planes of symmetry can be drawn through the perianth (cabbages, cloves, primroses);
2) zygomorphic (irregular) – only one plane of symmetry can be drawn through the perianth (legumes, Lamiaceae);
3) asymmetrical (asymmetrical) – no plane of symmetry can be drawn through the perianth (valerian officinalis, canna, horse chestnut, orchid).
Rice. 3. Types of flower symmetry:
1 – actinomorphic (regular) flower; 2 – zygomorphic (irregular) flower
Actinomorphic free-petalled corollas differ in the number of petals, their arrangement and the presence or absence of a marigold. Forms actinomorphic interpetalled corollas differ in the length of the tube, shape and size of the bend (Fig. 4):
1) rotate– the tube is small or practically absent, and the limb is turned almost into the same plane (forget-me-not, speedwell);
2) funnel-shaped– large funnel-shaped tube, small bend (tobacco, dope);
3) tubular– a cylindrical tube with an erect short bend (sunflowers, other asteraceae); a special case is a tubular corolla with a saucer-shaped wide limb (lilac, daffodil);
4) bell-shaped– the tube is spherical, cup-shaped, gradually turning into an inconspicuous limb (bell, lily of the valley);
5) cap-shaped– petals grow together at the top (grape).
Rice. 4. Basic forms of interpetal corollas:
A– tubular with a saucer-shaped bend (narcissus); B– funnel-shaped (tobacco); IN– two-lipped (white lily); G– wheel-shaped (Veronica dubravnaya); D– bell-shaped (bell-shaped); E– tubular (sunflower); AND– reed (calendula officinalis); AND– funnel-shaped (blue cornflower); TO– cap (grapes); 1 – corolla tube; 2 – bend; 3 – pharynx; 4 – crown (crown); 5 – ovary; 6 – bract leaf; 7 – stamens; 8 – sepal; 9 – corolla, falling off in the form of a cap
Zygomorphic corollas often have a special shape, which is a good morphological character of the species, genus or even family (the moth type of corolla in legumes). Among zygomorphic fused petal corollas most often found:
1) bilabiate– the limb consists of two parts: the upper and lower lips (jasmine, norichnikov);
2) reed– fused petals extend from the tube in the form of a tongue (dandelion, calendula);
3) spurred– the petals form a hollow outgrowth – a spur (sapula, toadflax); the spurred corolla can also be actinomorphic (catchment).
Fertile The (reproductive) part of the flower is represented by the androecium and gynoecium.
Androecium is a collection stamens one flower.
Gynoecium is a collection of carpels that form one or more pistils of one flower.
Based on the presence of fertile parts (stamens, pistils), flowers are classified into groups:
1) bisexual – these are flowers that have stamens and pistils (more than 70% of angiosperms have bisexual flowers);
2) same-sex - These are flowers that have only stamens or only pistils. Accordingly, unisexual flowers can be female (pistillate), which have pistils, and male (staminate), which have only stamens. Unisexual flowers can be placed either on one or on different copies of the same plant.
In this regard, they distinguish:
monoecious plants in which staminate and pistillate flowers are located on the same specimen (corn, cucumber, watermelon, alder). Monoecious plants make up 5–8%;
dioecious plants in which staminate and pistillate flowers develop on different specimens, i.e., female and male plants are distinguished (hemp, sea buckthorn, aspen, sour sorrel). There are only 3–4% of dioecious plants;
multi-household plants that, along with bisexual flowers, also have unisexual ones (buckwheat, ash, maple). There are 10–20% of such plants.
Most botanists believe that the most ancient angiosperms had bisexual flowers, and dioecious flowers arose later from bisexual ones. The main reason for the transition of bisexual flowers to dioecious flowers is an adaptation to more reliable cross-pollination. Sterile flowers often appear, which are placed around the periphery of the inflorescence and are intended to attract pollinating insects.
Directly, and during the subsequent sexual process, the ovules of flowering plants develop into seeds inside the ovary.
The flower, being a unique formation in its nature and functions, is amazingly diverse in structural details, color and size. The smallest flowers of plants of the duckweed family have a diameter of only about 1 mm, while the largest flower is that of Rafflesia Arnolda ( Rafflesia arnoldii family Rafflesiaceae), living in tropical forests on the island of Sumatra (Indonesia), reaches a diameter of 91 cm and weighs about 11 kg.
Hypotheses about the origin of the flower
From attempts to understand the origin of the most typical bisexual flower for angiosperms with a perianth arranged in one way or another, the main hypotheses of the origin of angiosperms (Angiospermae) as a taxon were born.
- Pseudo theory:
Time: beginning of the 20th century. Founders: A. Engler, R. Wettstein.
The theory is based on the idea of the origin of flowering plants from ephedra-like and oppressive-like gymnosperm ancestors. An original concept of the origin of the flower was developed - the idea of the independent emergence of flower parts as organs “sui generis”. It was assumed that the primary flowers of angiosperms were dioecious wind-pollinated flowers with a small and strictly fixed number of parts, and their further evolution followed a line from simple to complex.
- Strobilar or evanth theory:
Time: end of the 18th century - beginning of the 20th century. Founders: I. V. Goethe, O. P. Decandolle (typological constructions), N. Arber and J. Parkin.
According to this theory, the Mesozoic bennettites are closest to the desired ancestors of angiosperms, and the original type of flower seems similar to that observed in many modern polycarpids: a bisexual entomophilous flower with an elongated axis, a large and indefinite number of free parts. The further evolution of the flower within angiosperms was of a reductionist nature.
- Telome theory:
Time: since the 30s of the XX century. Founder: V. Zimmerman.
According to this theory, all organs of higher plants originate and independently develop from telomes; higher plants with true roots and shoots come from rhyniophytes, whose body was represented by a system of dichotomously branching simple cylindrical axial organs - telomes and mesomes. In the course of evolution, as a result of reversal, flattening, fusion and reduction of telomes, all organs of angiosperms arose. The leaves of seed plants arose from flattened and fused systems of telomes; stems - due to lateral fusion of telomes; roots are from underground telome systems. The main parts of the flower - stamens and pistils - arose from spore-bearing bodies and evolved independently of vegetative leaves.
Flower structure
The main parts of a blooming flower
The flower consists of stem part(peduncle and receptacle), leaf part(sepals, petals) and generative part(stamens, pistil or pistils). The flower occupies an apical position, but at the same time it can be located either at the top of the main shoot or at the lateral one. It is attached to the stem by pedicels . If the peduncle is greatly shortened or absent, the flower is called sedentary(plantain, verbena, clover). The pedicel also contains two (in dicotyledons) and one (in monocotyledons) small preleaves - bract, which may often be missing. The upper expanded part of the peduncle is called receptacle , on which all the organs of the flower are located. The receptacle can have different sizes and shapes - flat(peony), convex(strawberries, raspberries), concave(almond), extended(magnolia). In some plants, as a result of the fusion of the receptacle, the lower parts of the integument and the androecium, a special structure is formed - hypanthium . The shape of the hypanthium can be varied and sometimes participate in the formation of the fruit (cynarrhodium - rose hip, apple). Hypanthium is characteristic of representatives of the rose, gooseberry, saxifrage, and legume families.
The parts of a flower are divided into fertile, or reproductive (stamens, pistil or pistils), and sterile(perianth).
Perianth
Rudbeckia brilliantia flower
The corolla, as a rule, is the most noticeable part of the flower; it differs from the calyx in its larger size, variety of colors and shapes. Usually it is the corolla that creates the appearance of the flower. The color of the corolla petals is determined by various pigments: anthocyanin (pink, red, blue, purple), carotenoids (yellow, orange, red), anthochlor (lemon yellow), antopheine (brown). The white color is due to the absence of any pigments and the reflection of light rays. There is also no black pigment, and very dark colors of flowers are very condensed dark purple and dark red colors.
The aroma of flowers is created by volatile substances, mainly essential oils, which are formed in the epidermal cells of the petals and perianth leaves, and in some plants - in osmophores (special glands of various shapes that have secretory tissue). The released essential oils usually evaporate immediately.
The role of the corolla is to attract pollinating insects. In addition, the corolla, reflecting part of the spectrum of sunlight, protects the stamens and pistils from overheating during the day, and by closing at night, they create a chamber that prevents them from cooling or being damaged by cold dew.
Stamens (androecium)
Stamen- the male reproductive organ of an angiosperm flower. The collection of stamens is called androecium(from Greek aner, Genitive andros- "man" and oikіa- “dwelling”).
Most botanists believe that stamens are modified microsporophylls of some extinct gymnosperms.
The number of stamens in one flower varies widely among different angiosperms, from one (orchids) to several hundred (mimosas). As a rule, the number of stamens is constant for a particular species. Often the stamens located in the same flower have a different structure (in the shape or length of the stamen filaments).
Stamens can be free or fused. Based on the number of groups of fused stamens, different types of androecium are distinguished: brotherly if the stamens grow together into one group (lupine, camellia); bifraternal if the stamens grow together into two groups; polyfraternal if numerous stamens grow together into several groups; fraternal- the stamens remain unfused.
The stamen consists of filament, by means of which it is attached to the receptacle at its lower end, and anther at its upper end. The anther has two halves (thecae) connected liaison officer, which is a continuation of the filament. Each half is divided into two nests - two microsporangia. Anther nests are sometimes called pollen sacs. The outside of the anther is covered with epidermis with cuticle and stomata, then there is a layer of endothecium, due to which, when the anther dries, the nests open. The middle layer runs deeper in the young anther. The contents of the cells of the innermost layer are tapetuma- serves as food for developing mother cells of microspores (microsporocytes). In a mature anther, the partitions between the nests are most often absent, and the tapetum and middle layer disappear.
Two important processes occur in the anther: microsporogenesis and microgametogenesis. In some plants (flax, stork) some of the stamens become sterile. Such sterile stamens are called staminodes. Often the stamens function as nectaries (blueberries, blueberries, cloves).
Carpels (gynoecium)
The inner part of the flower is occupied carpels, or carpella. The collection of carpels of one flower forming one or more pistils is called gynoecium. The pistil is the most essential part of the flower from which the fruit is formed.
It is believed that carpels are structures in which the leaf nature of origin can be traced. However, functionally and morphologically they correspond not to vegetative leaves, but to leaves bearing megasporangia, that is, megasporophylls. Most morphologists believe that in the course of evolution, longitudinally folded (conduplicate) carpels arose from flat and open ones, which then fused at the edges and formed a pistil. The pistil occupies the central part of the flower. It consists of ovaries , column And stigma .
Variety of flowers
Cyclicality of a flower
In most plants, parts of the flower form clearly visible whorls or circles (cycles). The most common are five- and four-circular, that is, penta- and tetracyclic flowers. The number of flower parts on each circle may vary. Most often, flowers are pentacyclic: two circles of perianth (calyx and corolla), two circles of stamens (androecium) and one circle of carpels (gynoecium). This arrangement of flowers is typical for lilies, amaryllis, cloves, and geraniums. In tetracyclic flowers, two perianth circles usually develop: one circle of androecium and one circle of gynoecium (iris, orchids, buckthorns, euonymaceae, noricaceae, labiates, etc.).
Sometimes there is a decrease in the number of circles and members in them (integumentless, unisexual flowers) or an increase (especially in garden forms). A flower with an increased number of circles is called terry. Doubleness is usually associated either with the splitting of the petals during flower ontogenesis, or with the transformation of part of the stamens into petals.
Certain patterns appear in the structure of flowers, in particular multiple ratio rule. Its essence lies in the fact that in different circles of a flower there is the same or multiple number of members. In most monocots, three-membered flowers are most common, in dicotyledons - five-membered, less often two- or four-membered (cabbage, poppy) flowers. Deviation from this rule is often observed in the gynoecium circle; the number of its members is less than in other circles.
Flower symmetry
One of the characteristic features of the structure of a flower is its symmetry. According to their symmetry, flowers are divided into actinomorphic, or regular, through which several planes of symmetry can be drawn, each of which divides it into two equal parts (umbrella, cabbage), - and zygomorphic, or irregular, through which only one vertical plane of symmetry can be drawn (legumes, cereals).
If no plane of symmetry can be drawn through a flower, it is called asymmetrical, or asymmetrical(valerian officinalis, cannaceae).
By analogy with actinomorphy, zygomorphy and asymmetry of a flower as a whole, they also speak of actinomorphy, zygomorphy and asymmetry.
For a brief and conventional designation of the structure of flowers, formulas are used in which various morphological characteristics are encoded using alphabetic and numerical designations: the sex and symmetry of the flower, the number of circles in the flower, as well as the number of members in each circle, the fusion of parts of the flower and the position of the pistils (upper or inferior ovary).
The most complete picture of the structure of a flower is given by diagrams that represent a schematic projection of the flower onto a plane perpendicular to the axis of the flower and passing through the covering leaf and axis
Flower structure. The main and unique feature of angiosperms is their ability to form shortened and modified flower shoots. There is still debate regarding the origin of the flower, but the most widespread hypothesis is that the flower, like the strobili of gymnosperms, arose from the spore-bearing shoots of primitive gymnosperms, most likely seed ferns. They did not yet have strobili, so the flower initially could not have come from cones, but arose independently. Subsequently, the evolution of strobili of gymnosperms and flowers of angiosperms took place independently of each other. Flowers consist of various parts, which together form an amazingly organized system that ensures the complex processes of reproduction, both asexual and sexual (Fig. 255).
Rice. 2 5 5. Flower structure diagram:
1 - peduncle: 2 - receptacle: 3 - sepal: 4 - petal;
5 - stamen: b - pistil (according to V. G. Khrzhanovsky et al.)
The flower always occupies an apical position, but at the same time it can be located either at the top of the main shoot or at the lateral one. Relatively elongated internode- peduncle-connects the flower with the rest of the plant. But in many species it is absent or greatly shortened. In such cases, the flowers are called sessile. The expanded distal part of the pedicel is called receptacle Usually it is flattened, but sometimes it can be concave or, conversely, convex). The receptacle is the axis of the flower, only greatly shortened, and all the organs of the flower are located in the pauses of its very short internodes. Some of them have generative functions, while others are intended only to best ensure the occurrence of reproduction processes. Let's look at them in order.
A - concave in rosehip (Rosa canina); B - flat at the peony (R. Raeopa); IN - convex in buttercup (Ranunculus sceleratus) (according to V. G. Khrzhanovsky et al.
Parts of a flower and their functions. Perianth. Perianth make up calyx and corolla. In the vast majority of plants, they are present in the flower simultaneously; such a perianth is called double( Fig. 257.), if there is only a calyx or only a corolla (which happens more often) - simple(Fig. 258.). Finally, in a small number of species the flower is completely devoid of perianth and is therefore called coverless, or naked(Fig. 259.). Calyx ( Calex) is formed from various amounts sepals(lat.sepalum) .They come from ordinary vegetative leaves and are very often green in color, which is why they photosynthesize. However, the main function of the sepals is not to supply the plant with organic substances, but to protect the developing parts of the flower before it blooms. In the absence of a corolla, the sepals take on a petal-like shape and are brightly colored (for example, in some ranunculaceae). Sometimes they perform some other functions and, in accordance with them, undergo various morphological transformations. The sepals can be separate from each other or fused together.
Rice. 2 5 7. Flower parts:
A - a flower with a double perianth, many stamens and an apocarpous gynoecium (buttercup); B - a flower with a double perianth, many stamens, an early calyx and a coenocarpous polycarpous gynoecium (poppy); IN - a flower with a double perianth, the sepals at the base are fused with the receptacle and form a depression in which there is a gynoecium, consisting of one carpel, there are many stamens, they are attached to the edge of the receptacle (plum); G - flower with a fused-leaved calyx and a fused-petalled corolla (lilac);
1 - peduncle; 2 - calyx; 3 - corolla tube (in the fused petal corolla); 4 - share of the corolla (in the corolla); 5 - mouth of the corolla (according to V.Kh. Tutayuk, with modifications)
Rice. 258. Simple perianths:
A - corolla-shaped - in goose onions (Gagea lutea); B - cup-shaped - in beets (Beta vulgaris) (according to V. G. Khrzhanovsky et al.)
whisk(Corolla) formed by varying numbers of petals (lat. petalum). Their origin may also be associated with vegetative leaves, but in most species they are flattened and expanded sterile stamens. In many angiosperms (for example, pink, carnation poppies and DR-) within the same flower, various transitional forms from stamens to petals are visible. Often, during the formation of a petal from a stamen, disturbances occur, resulting in double petals. Breeders of cultivated flowers have noticed this circumstance and use it to develop the desired forms.
Rice. 2 5 9. Flowers without perianth (naked):
A - calla palustris; B - ash (p. Fraxinus); B - willows (p. Salix) (A, B - bisexual; IN - dioecious): 1 - cover sheet; 2 - nectary (according to V. G. Khrzhanovsky et al.)
Rice. 260. Flowers with a crown:
A - narcissus (Narcissus pseudonarcissus):
B - passionflower (p. Passiflora);
1 - crown (according to V. G. Khrzhanovsky et al.)
Rice. 261. Shapes of fused-petalled actinomorphic corollas: A, B - funnel-shaped [A - in tobacco (Nicotiana tabacum); B - in bindweed (Convolvulus arvensis)]: B - tube-shaped - in sunflower (Helianthus ahnuus); G - saucer-shaped - in lilac (p. Syringa): 1 - limb; 2 - pharynx;
3 - tube; D - spicate - in loosestrife (p. Lysimachia);
B - bell-shaped - in lily of the valley (Convallaria majalis); F - cap - in grapes (Vitis vinifera) (according to V. G. Khrzhanovsky et al.
Additional structures are sometimes formed near the base of the petals, which are collectively called crowned(Fig. 260). Like the sepals, the petals of the corolla can grow together at the edges (interpetaled whisk - rice. 261 and fig. 262) or stay free (free petal whisk). It should be noted that a fused-leaved calyx does not necessarily entail the presence of a fused-petalled corolla (and vice versa). Often, a fused calyx is adjacent to a free-petalled corolla, or free sepals are combined with fused petals of the corolla.
The corolla is especially well developed in flowers pollinated by insects. Typically, their petals are very large and brightly colored, as this is necessary to attract desirable pollinators. Another way to attract the attention of insects is to use plants with small and relatively inconspicuous flowers. Their flowers gather in large inflorescences and together make themselves felt. In wind-pollinated angiosperms, the corolla is relatively weakly developed or even reduced.
They use formulas and diagrams that give a visual representation of its structure.
Flower formula- this is a symbol for the structure of a flower using letters, numbers and signs.
When drawing up the formula, use the following notation:
Ca- calyx ( Calyx);
Co- corolla ( Corolla);
R- simple perianth ( Perigonium);
A- androecium, a collection of stamens ( Androeceum);
G- gynoecium, a collection of pistils ( Gynoeceum);
* - actinomorphic flower;
Zygomorphic flower;
? - bisexual flower (usually it is omitted in the formula);
? - female (pistillate) flower;
? - male (staminate) flower;
() - brackets mean the fusion of flower parts;
Plus indicates the arrangement of flower parts in two or more circles (for example, R 3+3 - simple perianth, of 6 leaflets arranged in two circles) or the fact that the parts separated by this sign differ from each other ( A 1+(9) - androecium consists of one free and nine fused stamens);
Ca 5- the number next to the symbol indicates the number of members of this part of the flower ( Sa 5 - calyx of 5 free sepals);
∞ - if the number of members of a given part of the flower is more than 12, then their number is indicated by an infinity sign (for example, A ∞- the number of stamens is more than 12).
The formulas also note ovary type by location on the receptacle (upper, lower, middle):
G 1- a line above the number means that the ovary is inferior;
G 1- line under the number - superior ovary;
G 1--- a line from the number - the ovary is semi-inferior.
Examples of flower formulas are given below.
* ? Sa 4 Co 4 A 2+4 G(2) - formula of the cabbage flower: actinomorphic, bisexual; double perianth, in which the calyx consists of 4 free sepals, the corolla - of 4 free petals; androecium has 4 long and 2 short stamens (quadruple androecium); The gynoecium is simple, coenocarpous, formed by 2 carpels (1 pistil - from 2 carpels), the ovary is superior.
? Sa (5) Co (2+3) A 2+2 G(2) - formula of the white claret flower: zygomorphic, bisexual; double perianth, in which the calyx consists of 5 fused sepals, and the corolla - of 5 fused petals (2 petals form the upper lip, and the other 3 petals form the lower lip); the androecium is formed by 4 free stamens, of which 2 are long and 2 are short (double androecium); The gynoecium is simple, coenocarpous, formed by 2 carpels (1 pistil - from 2 carpels), the ovary is superior.
* ? R 3+3 A 3+3 G(3) - lily flower formula: actinomorphic, bisexual; a simple perianth consists of 6 leaflets, which are arranged 3 in 2 circles (simple corolla-shaped perianth); androecium consists of 6 free stamens, arranged 3 in 2 circles; The gynoecium is simple, coenocarpous, formed by 3 carpels (1 pistil - from 3 carpels), the ovary is superior.
? Sa (5) Co 1+2+(2) A (9)+1 G 1 - pea flower formula: zygomorphic, bisexual; double perianth, in which the calyx consists of 5 fused sepals, the petals have different shapes and sizes: one large petal - a sail, two free lateral ones - oars (wings) and two fused ones - a boat (moth-type corolla); the androecium consists of 10 stamens, of which 9 are fused into a tube and 1 is free - bifraternal androecium; The gynoecium is simple, monocarpous (1 pistil is formed by 1 carpel), the ovary is superior.
Flower diagram more clear than the formula. It represents a conventional schematic projection of the parts of a flower onto a plane and reflects their number, relative sizes and relative position, as well as the presence of accretion (Fig. 16, 17).
The diagram indicates the location of the covering (bract) leaf, bracts and the axis of the inflorescence or shoot bearing the flower. The bract, bracts and sepals are depicted in brackets with a keel (curly brackets) of various sizes, the petals - in round brackets, the stamens - in the form of a section through the anther or in the form of a shaded ellipse, the gynoecium - also in the form of a section through the ovary with a drawing of the placentation site and ovules, through which the cut has passed.
The diagram is designed so that the covering leaf is at the bottom, the axis of the inflorescence is at the top, and between them the parts of the flower are located in circles with conventional signs. When parts of a flower grow together in a diagram, the symbols are connected to each other by a line.
Rice. 16. Constructing a flower diagram:
1 - inflorescence axis;
2 - bract;
3 - sepal;
4 - petal;
5 - stamen;
6 - gynoecium;
7 - covering sheet.
Rice. 17. Flower diagrams:
A- magnolia (acyclic flower); B- Red currants; IN- black mustard; G- white jasmine; D- common bean; E- a typical flower of cereals; 1 , 5 - calyx; 2 - whisk; 3 , 8 - stamens; 4 , 9 - gynoecium; 6 - lower lip of 3 petals; 7 - upper lip of 2 petals; 10 - sail; 11 - oars; 12 - boat; 13 - difraternal androecium; 14 - lower flower scales; 15 - upper flower scales; 16 - lodicules
The most amazing and beautiful part of modern flowering plants is the flower. Different plants have different flowers: some are large and fragrant, others are small and inconspicuous. But all flowers on our planet perform the same function - reproduction. For this function in any flowering plant, two organs are responsible, which each flower contains - the pistil and the stamen. Each plant has its own characteristics of the location of these reproductive organs.
Inflorescences
Flowers grow on shoots. Evolution has optimized the reproductive process, and often a shoot produces several branches, each of which produces a separate flower. This form of flower formation is called an inflorescence.
Inflorescences can be complex or simple. Simple floral assemblages collect all the flowers on the main axis of the shoot. Complex inflorescences are characterized by the fact that on the main axis there are not individual flowers, but small branched inflorescences that reflect the structure of the flower. A diagram of a typical inflorescence is shown below:
Large flowers usually grow singly. Smaller flowers are collected in inflorescences. Collected together, they give the inflorescence structure and color, saturating the air around them with the aroma of nectar. This wonderful smell attracts insects that rush to the flower and in passing transfer pollen from one flower to another.
The inflorescence also produces more seeds and fruits than single flowers. In this way, the likelihood of a greater distribution of a particular plant species on earth is achieved. This is the biological significance of the formation of inflorescences.
Inflorescences-flowers
Some inflorescences in the process of evolution began to look like one huge single flower. This is how sunflower, chamomile, cornflower, viburnum, dahlia and many other famous plants bloom. Insects and animals that collect nectar pay attention to such large and bright flowers. Therefore, animal pollinators can pollinate several inflorescences at once.
Flower structure
The flower diagram presented below gives an idea of the typical structure of this organ. The flowers of various plants are located on the stalk. This is the name of the last node on the stem of a plant. The place where, like on the palm of your hand, the flower itself blooms is called the receptacle. This organ is the frame on which the structure of the flower is based. The receptacle is surrounded by perianth, which protects the pistil and stamen and attracts insects to this flower.
Some perianths form a corolla. This is the name given to the collection of inner petals of a flower that have a bright, contrasting color. The corolla serves to visually attract insects that collect pollen.
A diagram of a typical flowering plant is shown below.
1- petal;
2- filament;
3- boot;
4- stigma;
5- column;
6- ovary;
7- ovules
This entire complex structure is designed to perform the reproductive function. The main organs responsible for the appearance of the fruit are the stamen and pistil. For an example and comparison of these parts of a flower, let’s look at how they are arranged in a tulip and cherry.
Structure of the stamen and pistil
Cherry and tulip are completely different plants; even a child cannot confuse them. However, the stamen and pistil of these flora representatives have much in common. Both species belong to the kingdom Angiosperms. The tulip pistil does not have a style, and the stigma sits directly on the top of the ovary. The stigma is never smooth. Usually it is rough, branched, sometimes even sticky. Such difficulties in the structure of the stigma are due to the fact that it needs to collect as much pollen as possible and leave behind it for fertilization. Sometimes the stigma is located high on the style - at a higher height it is much better to catch pollen.
The pistil and stamen, the diagram of which is presented below, reflect the typical structure of the reproductive organs of an angiosperm.
The ovary is the expanded, lower part of the pistil. It contains the female eggs of the plant - the ovules. In this part of the pistil, the rudiments of future seeds and fruits ripen. A cherry has one ovule, while a tulip has several dozen. Therefore, all cherry fruits are single-seeded, while tulips develop and ripen many seeds at the same time.
Both the tulip and the cherry have the same types of stamens. They consist of a thin filament and a large anther. A large accumulation of pollen is formed inside the anther, in which each speck of dust is a separate male reproductive cell. A cherry flower has many stamens, but a tulip has only six. The transfer of plant pollen from the anthers to the stigma is called pollination. After the pollen has settled on the stigma, fertilization occurs - male reproductive cells merge with female ones, giving life to a new fruit.
As can be seen from the description, both the stamen and the pistil are equally important for fertilization. It is in the pistil that the fruit is born, so this organ of the plant is the female part of the flower. The stamens, in turn, are called the male part of the flower.
Male and female flowers
In the cherry and tulip examples discussed above, a stamen and pistil were contained in each flower of that plant. Such representatives of the plant world are called bisexual. But some plants have flowers with either stamens or only pistils. Such representatives of our flora are called unisexual. Among the unisexual plants are cucumbers, mulberries, poplars, and sea buckthorn. Each individual specimen of a unisexual species has either male or female flowers.
Designation of male and female plants
In botany, it is customary to designate pistillate (female) flowers with the astrological symbol of Venus. And the male (staminate) ones are marked with the sign of Mars.
Monoecious and dioecious
Staminate and pistillate flowers are quite often located on the same plant. Thus, a given tree or bush is capable of self-pollinating and reproducing without outside help. Plants that have this quality are called monoecious. Typical monoecious plants are cucumbers, pumpkin, hazel. In other representatives of the plant world, stamens and pistils are located on different plant specimens. This feature allowed botanists to classify these specimens as dioecious plants. Dioecious species such as willow, nettle, poplar, and aspen are widespread.
Urban residents of the central zone of our country are familiar with poplar - a typical dioecious plant. In spring, poplars shed pollen, and in early summer, female specimens of this species shed white fluff. The well-known white clouds are parachutes with the help of which the poplar spreads its seeds. Thin lacy threads of fluff allow the seed to better stay in the air and fly away from the parent tree at a considerable distance. The same method of distributing its own fruits is inherent in dandelions.
Results
Stamens and pistils are the most important components of any flowering plant. Understanding the distribution of plants in nature is important in many areas of our daily lives. For example, the method of propagation of poplars described above leads to numerous allergic diseases. Planting only male specimens of this plant can significantly reduce the number of sick leaves at city enterprises and improve the health of residents of a given locality.