Which leaves of carrots are simple or complex. The external structure of the leaf. Why can carrot leaves dry

In the leaves, a process occurs that distinguishes plants from animals - the formation of organic substances. Leaves are involved in water evaporation and gas exchange.

The leaf is the lateral part of the shoot. It consists of a leaf blade, petiole, base and stipules.

The leaf blade is the expanded part of the leaf. At the bottom, it passes into the petiole - the narrowed stem-like part of the leaf. The petiole has elasticity, which makes hail, raindrops, and gusts of wind less noticeable. The lower part of the petiole passes into the base of the leaf, which connects the leaf to the stem node.

Outgrowths - stipules are often formed on the basis of the leaf. There are usually two of them, they are free or grow together with the petiole. Stipules can be green, like a leaf blade, or transparent. In some plants (birch, bird cherry, linden), stipules fall off early, and they are absent on adult leaves. There are plants (caragana, or yellow acacia), in which stipules are modified into spines and protect plants from being eaten by animals. At the same time, many plants do not have stipules (lily of the valley, lilac, shepherd's purse).

In plants whose leaves do not have petioles, the plate immediately passes into the base (flax, carnation). A leaf with a petiole is called petiolate, and without a petiole, it is called sessile.

In a number of plants (carrots, wheat, oats), the base of the leaf grows and covers the stem.

The leaves of different plants differ from each other in the number of leaf blades. A leaf with one leaf blade is called simple, and a leaf with several blades located on a common petiole is called complex. Each blade of a compound leaf is called a leaflet.

leaf arrangement

The arrangement of leaves on is called leaf arrangement. At the next leaf arrangement, one leaf departs from each node of the stem (linden, apple, birch). With the opposite, the leaves are placed on each node in pairs, one against the other (lilac, maple, nettle). There are plants that have three or more leaves on one node (crow's eye, bedstraw, oleander) - this is whorled

Carrot - biennial herbaceous plant celery family (Apiaceae). Cultivated carrots are a biennial plant of the umbrella family (Umbelliferae). In the first year of life, carrots develop a basal rosette of leaves with dormant axillary buds and a thick root (root crop). For the second year life cycle stem formation, flowering and seed formation.

The structure of the root system. The root of a carrot is a thickening of the root and stem. It consists of three parts - the head, the neck and the root itself. The head is formed from the supracotyloid knee and is a stem with strongly shortened internodes. Leaves develop on it, forming a rosette, with axillary buds. The neck is the middle part of the root, free from leaves and filamentous roots. It is formed due to the growth of the hypocotyl knee. Actually the root, the lower part of the root, which develops due to the thickening of the main tap root.

The taproot (central) root consists of bark (pulp) and core (wood). On the surface of the bark are lenticels (recesses), through which air enters the root crop. The more bark and less core, the higher the quality of carrot roots. Between the core and the bark there is a cambial layer of cells that are able to divide, which is why the growth of the root crop occurs. In the inner part of the bark, thin lateral roots with a mass of root hairs originate. The bulk of the roots is located at a depth of 25 ... 30 centimeters, and some penetrate to a depth of 2 meters.

The root crop comes in various lengths and shapes - elliptical, conical and cylindrical. The color of the root crop is orange, orange-red, less often yellow.

Varieties that have a red-orange color are called carotenes. Carotene varieties are the most valuable and therefore widely distributed. Diagram of the structure of a carrot root.

H is the length of the root crop; h - head length; h1 - root neck length; h2 - the length of the actual root; h 3 - the length of the lower part of the root with a diameter of less than 1 centimeter; D - largest diameter; D1 - root diameter in the middle of its length.

The size of the wood is determined by the percentage of the diameter of the wood to the diameter of the root (D). The wood is small if this ratio is less than 50%, medium - about 50%, large - more than 50%. Wood cross-section configuration: rounded, rounded-faceted, faceted, star-shaped.

On the cross section of the root crop, two parts are distinguished: the upper one is a thick layer of bark (pulp, phloem), the inner one is the core (wood, xylem). Between the bark and the core is a thin layer of cambium.

Varieties of carrots with a small core and thick bark are more valuable, since the flesh has better nutritional qualities than the core. by the most high quality have varieties in which the small core is colored the same as the root bark.

By mass, carrot roots are divided into small weighing up to 100 grams, medium 100 ... 150 grams and large more than 150 grams.

The structure of the leaf rosette and leaves. The shape of the leaf rosette in carrot plants is upright, semi-raised or spreading. The size of the rosette depends on the size and number of leaves in it. A rosette is considered small when it contains 6–10 leaves, an average rosette has 10–15 leaves, and a large one has 16–20 leaves.

The leaves of carrots are long-petiolate, pinnately dissected. The dissection of the leaf blade can be expressed in varying degrees: slightly dissected, medium dissected and strongly dissected. The leaf segments are lanceolate-linear, lanceolate, sharp-crested and lobed.

1 - lanceolate-linear; 2 - lanceolate; 3 - sharp-edged; 4 - bladed.

The color of the leaves is light green, green, dark green, gray-green, purple-green.

Leaf petiole pubescence - sparse hard, sparse soft, dense hard, dense soft or completely absent.

A seed plant is formed from the root crop in the second year, which consists of the main stem of a first-order shoot with a central umbrella. Shoots extending from the main stem and formed from buds located in the axils of rosette leaves are second-order shoots. The former are called stem, the latter are rosette. On them, in turn, shoots of the third and fourth orders are formed.

Each of the shoots ends with an inflorescence - a complex umbrella, which consists of simple umbrellas, each of which has several dozen flowers. By the time of flowering, the height of the seed bush with branched seed shoots reaches 1 meter.

The structure of flowers, flowering, fruit formation and seed maturation. The flowers are small, bisexual, with a lower bilocular ovary. They are collected in complex umbrellas. Cross-pollination is carried out mainly by insects and wind. Flowering begins 45 ... 55 days after planting the seed plants. The central umbrella blooms first, and then the umbrellas of subsequent orders. Each next order of umbrellas blooms only after the previous one has faded. The flowering of the main umbel lasts 11...13 days; the second order umbels - 11...12 days, the third - 13...16 days, the fourth - 18...19 days.

In each umbel, flowering begins with peripheral umbels and spreads to the center, and in each umbel, from peripheral flowers. In general, carrots on the seed plot bloom for about 40 days.

Carrot is a cross-pollinating plant. It is pollinated by bees, flies, beetles and other insects.

The fruit of the carrot is a dry two-seeded, when ripe it splits into two lobes. From the moment of fertilization to the maturation of seeds, 60 ... 65 days pass. The length of the seed is about 3 millimeters, the width is 1.5 millimeters, the thickness is 0.4 ... 1 millimeter. On each side, the seed has four to five ribs with thin spines.

Carrot seeds are very small, in 1 kilogram there are up to 500 thousand with spikes (not rubbed) seeds and up to 900 thousand rubbed, the weight of 1000 seeds is 1.1 ... 1.5 grams.

Carrot is a biennial plant. This means that in the first year a rosette of leaves and a storage organ are formed - a thickened fleshy root (root crop). In the second year, stems, inflorescences, flowers, fruits and seeds are formed, after which the plant dies. The most valuable part of the plant is the root.

The root system of carrots is pivotal, penetrating deep into the soil. The shape of root crops can be round, oval, truncated-conical, conical and cylindrical. The size of the root crop is short (less than 10 cm), medium (11-15 cm), long (more than 15 cm). In Russia, the length of the root crop rarely exceeds 30-40 cm, but it is known that carrots are grown in Mexico, the root crops of which reach 2 meters.

By diameter, root crops are divided into thin (less than 2.5 cm), medium (2.6-4 cm), thick (more than 4 cm). At optimal conditions growing, depending on the varietal characteristics, their mass grows small (less than 80 g), medium (80-150 g) or large (more than 150 g). In areas with loose fertile soil, the mass of root crops can be 300-500 g or more.

The color of the surface of the root in the most common varieties is orange, red-orange, red, pink-orange, and in rare varieties - white, light green, yellow, purple. The surface of root crops is smooth, uneven, bumpy. Small or deep eyes are clearly visible on it.

The root crop is fleshy, its woody part (core) is coarser and less sugary than the bark (top layer). The latter is more brightly colored, and only in some varieties (for example, in Nantes 4) the core and bark have the same bright color. The shape of the core is clearly visible on the cross section of the root crop. It can be round, rounded-angular, faceted, star-shaped. The size of the core is considered small if it is less than 30% of the root diameter, medium - 30-50% and large - more than 50%.

Rosette leaves of carrots are simple, pinnately dissected, with petioles. The contour of the plate is rhombic or triangular. The shape of the rosette of carrot leaves can be semi-erect, sprawling or pressed. Leaf petioles are long, thin, grooved, glabrous or pubescent, light green, glaucous, sometimes with anthocyanin pigmentation. The color of the plate is green, in Asian forms it is dark green, often gray-green.

Carrot flowering is observed in the second year of the plant's life. The height of the stems by the beginning of flowering reaches 1 m. The stems are fistulate, ribbed, bare or pubescent, branched, green or yellow-green. Each stem bears an inflorescence - a complex umbrella, consisting of individual small umbrellas.

In most plants, the flowers are small, bisexual, but male-sterile forms are often found.

What is the importance of leaves in plant life? To answer this question, get acquainted with the structure of the leaf and the life processes that take place in it.

Compare the juicy, fleshy, spiky leaves of the agave with the wide, dense, leathery leaves of the ficus.

How different are the leaves of these indoor plants! Remember delicate, almost lacy carrot leaves and large cabbage leaves curling into a head. Even the leaves of the most common trees and shrubs are so different that it is difficult to confuse the leaves of birch and linden, maple and oak.

There are very large and very small leaves. In the Moscow Botanical Gardens, the tropical aquatic plant Victoria Cruciana blooms every summer. Its leaves are so large that a three-year-old child sits on them, like on a raft, and the leaf floats freely on the water. And in the weed woodlice, the leaves are smaller than the nail. In some plants, the leaves have become tiny green scales or spines, as in cacti, camel thorn, and many other dryland plants.

Outwardly, the leaves of different plants are very different from each other, but there is much in common between them.

In most plants, the leaves are green in color and consist ofleaf blade and petiole with which they are attached to the stem. Some plants do not have petioles. The leafless leaves are called sedentary. Such leaves are found in agave, flax, agave and many other plants. Leaves with petioles petiolate - are present in almost all of our trees: birch, oak, maple, linden, ash and many others. Sometimes at the base of the leaf petiole develop stipules.

According to the shape of the leaf blade, the leaves can be round, oval, lanceolate, linear, etc.

Distinguish between the leaves and the shape of the edge of their plate. For example, the edge of the plate may be serrated, like a birch. The edge of the leaf blade can be solid, like a lilac, and then the leaf is called whole-edge.

There are leaves with serrated, notched, crenate, wavy doubly-toothed and doubly-serrated edges. Consider the shape of the edge of the sheet in the figure.

Have you ever had to find unusual leaves consisting of only veins among last year's foliage darkened under the snow in the spring? The juicy soft green of the leaf blade rotted over the winter, and the more durable veins well preserved and visible.

The veins can also be seen on a living green leaf, especially when the leaf is held up to light. On the underside of the leaf blade, the veins are more visible than on top.

Water and substances dissolved in it move along the veins. The special fibers of the veins give the leaves strength and elasticity. Sieve tubes also lie in the veins, through which organic substances flow from the leaves to all organs of the plant.

In the leaves of some plants, the veins are parallel to one another. Such venation is called parallel. It is found in almost all monocotyledonous plants, such as wheat, rye, barley, corn, onions, and some others.

The leaves of the lily of the valley and the houseplant aspidistra, or "friendly family", havearcuate venation.Arc venation, as well as parallel, usually in monocotyledonous plants.

Dicotyledonous plants are more likely to have palmate or pinnate venation.

In the case of pinnate venation, a large main vein passes in the middle of the leaf, and smaller side veins depart from it, like in oak. At palmate venation of several main veins of the same thickness disperse to the sides of the base of the leaf blade, like a maple, nasturtium, cuffs and others. With palmate And in pinnate venation, the veins can branch repeatedly And, connecting with each other, howl thick mesh. If the main veins are weakly expressed, then the venation is called cirrus-reticulate or palmate-reticulate. Take a look on the leaves of maple, linden, apple or indoor plants such as geranium, lemon, begonia, primrose, rose. All these dicot plants- mesh venation. By venation, it is easy to decide which plant is in front of you: monocot or dicot. But there are exceptions. For example, In a monocotyledonous plant, the crow's eye, the leaves have a net venation.