All plants are composed of vegetative and generative organs. The latter are responsible for reproduction. In angiosperms, this is a flower. It is a modified escape. The vegetative organs of the plant are the root system and shoots. The root system consists of the main root, lateral and additional. Sometimes the main root can be unexpressed. Such a system is called fibrous. Shoots consist of stems, leaves and buds. The stems provide the transport of substances, and also support the position of the plant. The buds are responsible for the formation of new shoots, as well as flowers. The leaf is the most important organ of the plant, as it is responsible for photosynthesis.
How it works
Simple and complex leaves consist of several types of fabrics. Let's take a closer look at them.
From the point of view of histology
Above is the integumentary tissue - the epidermis. This layer is one or two cells thick with dense shells located very close to each other. This fabric protects the sheet from mechanical damage, and also prevents excessive evaporation of water from the body. In addition, the epidermis is involved in gas exchange. For this, stomata are present in the tissue.
On top of the epidermis is also an additional protective layer, which consists of wax secreted by the cells of the integumentary tissue.
Under the epidermis is a columnar, or assimilation parenchyma. This is the main fabric of the sheet. The process of photosynthesis takes place in it. Parenchyma cells are located vertically. They contain a large number of chloroplasts.
Under the assimilation tissue is a conductive sheet system, as well as a spongy parenchyma. Conductive tissues are xylem and phloem. The first consists of vessels - dead cells connected vertically to each other, without horizontal partitions. By xylem, water with substances dissolved in it enters the leaf from the root. The phloem consists of sieve tubes - elongated living cells. Through this conductive tissue, solutions are transported, on the contrary, from leaf to root.
Spongy tissue is responsible for gas exchange and water evaporation.
Under the listed layers is the lower epidermis. He, like the top one, performs a protective function. It also has stomata.
Leaf structure
From the stem leaves the stalk, on which the leaf blade is attached - the main part of the leaf. Veins extend from the petiole to the edges of the leaf. In addition, stipules are located in its connections with the stem. Complex leaves, examples of which will be discussed below, are arranged in such a way that there are several leaf plates on one petiole.
What are the leaves
Depending on the structure, simple and complex leaves can be distinguished. Simple consists of one plate. A composite sheet is one that consists of several plates. It can be diverse in structure.
Types of Complex Leaves
There are several types. The factors for dividing them into species can be the number of plates, the shape of the edges of the plates, and the shape of the sheet. It is of five types.
Leaf shape - what it is
There are such types of it:
- swept;
- oval;
- ring-shaped;
- linear
- heart-shaped;
- fan-shaped (semicircular leaf);
- pointy;
- needle;
- wedge-shaped (triangular leaf, attached to the stem at the top);
- spear-shaped (sharp with thorns);
- spade;
- lobed (the sheet is divided into several blades);
- lanceolate (long, wide in the middle of the leaf);
- reverse lanceolate (the upper part of the sheet is wider than the lower);
- reverse heart-shaped (a leaf in the shape of a heart, attached to the stem with a sharp end);
- diamond-shaped;
- sickle-shaped.
A composite sheet may have plates of any of the above forms.
The shape of the edges of the plates
This is another factor that allows you to characterize a complex sheet.
Depending on the shape of the edges of the plates, there are five types of leaves:
- toothed;
- small town;
- serrated;
- notched;
- all-edge.
Other types of compound leaves
Depending on the number of plates and their location, the following types of complex leaves are distinguished:
- palmate;
- cirrus;
- bifibrous;
- trefoil;
- piercing.
In palmate complex leaves, all plates diverge in radius from the petiole, resembling fingers in their appearance.
Cirrus leaves have leaf plates located along the petiole. They are divided into two types: paired and unpaired. The former do not have an apical plate; their number is a multiple of two. In unpaired pinnate apical plate is present.
In bifibrous leaves, plates are located along the secondary petioles. Those, in turn, are attached to the main thing.
Three-leafed have three plates.
Cirrus leaves are similar to cirrus.
Complex leaves - their venation
There are three types of it:
- Parallel. Veins run exactly from the base of the sheet to its edges along the entire plate.
- Arc. Veins go not smoothly, but in the form of an arc.
- Mesh. It is divided into three subspecies: radial, palmate and pericervical. With radial venation, the leaf has three main veins, from which the rest depart. Palmate is characterized by the presence of more than three main veins, which are separated not far from the base of the petiole. With the pericervical leaf, it has one main vein, from which the rest depart.
Most often, a complex leaf has a mesh venation.
Arrangement of leaves on the stem
Both simple and complex leaves can be arranged in different ways. There are four types of location:
- Whorled. The leaves are attached in three pieces to a narrow stem - whorl. They can be cross, with each whorl rotated 90 degrees relative to the previous one. Plants with this arrangement of leaves are Elodea, the raven eye.
- Outlet. All leaves are at the same height and are arranged in a circle. Agave, chlorophytum has such sockets.
- Sequential (next). Leaves are attached one for each node. Thus, they are located near birch, pelargonium, apple tree, rose.
- The opposite. With this type of arrangement, there are two sheets on each node. Each node is usually rotated relative to the previous 90 degrees. Also, the leaves can be arranged in two rows without turning the nodes. Examples of plants with this arrangement of leaves are mint, jasmine, lilac, fuchsia, and cedar.
The first two types of leaf arrangement are typical for plants with simple leaves. But the second two species can relate to complex leaves.
Plant examples
Now let's look at different types of complex leaves with examples. They emit a sufficient amount. Plants with complex leaves can be of various life forms. It can be both bushes and trees.
Very common plants with complex leaves - ash. These are trees of the olive family, dicotyledonous class, angiosperms. They have unpaired compound leaves with seven to fifteen plates. The shape of the edge is serrated. Venation - mesh. Ash leaves are used in medicine as a diuretic.
A striking example of a bush with complex leaves can be called raspberries. These plants have unpaired leaves with three to seven plates on long petioles. The type of venation is perinatal. The shape of the edge of the sheet is crustacean. Raspberry leaves are also used in folk medicine. They contain substances with anti-inflammatory effect.
Another tree with complex leaves is mountain ash. Her leaves are paramorous. The number of plates is about eleven. Venation is pericervical.
The next example is clover. It has complex triple leaves. Clover venation netted. The shape of the edge of the sheet is solid. In addition to clover, the bobover also has triple leaves.
Complex leaves also have such a plant as albicia. It has bifurcated leaves.
Another striking example of a plant with complex leaves is acacia. This bush has a mesh venation. The shape of the edge is solid. The type of leaf is bilobate. The number of plates is from eleven pieces.
Another plant with complex leaves is strawberries. Type of sheet - three leaf. Venation - mesh. These leaves are also used in folk medicine. Usually with atherosclerosis and other vascular diseases.
Conclusion
As a conclusion, we give a general table about complex leaves.
Complex leaves, examples, description| Hard Sheet Type | Description | Plant examples |
| Palmate leaves | The plates diverge from the petiole in a fan, resembling human fingers | Horse Chestnut |
| Pinnate | The number of plates is odd, apical is present. All plates are located along the main petiole. | Ash, rose, mountain ash, acacia |
| Pinnate | The number of leaf plates is odd, the apical is absent. All of them are located along the main petiole. | Peas, sweet peas |
| Bifurcate | The plates are attached to the secondary petioles growing from the main petiole. | Albitsia |
| Triple (three leaf) | They have three plates that extend from the main petiole | Clover, beaver |
| Cranked | The plates are arranged like cirrus, but not completely separated | Rowan |
So we examined the structure of a complex leaf, its species, examples of plants that possess them.