The composition of the leaves, what the leaves are made of

1 The epidermis is wrapped around the outside of the leaf, usually in one layer, the upper one is called the upper epidermis, and the lower one is called the lower epidermis.

The epidermis is made up of a tightly packed, colorless, transparent layer of cells. Epidermal cells are generally irregularly shaped, flat bodies, with uneven side walls that are chimeric to each other, tightly connected, without intercellular spaces, and a layer of cuticle on the outer wall of epidermal cells that is also transparent and impermeable. These paired half-moon-shaped cells on the epidermis are called guard cells.

Usually the upper epidermis has fewer guard cells than the lower epidermis. The green granules in guard cells are chloroplasts. Chloroplasts are present in guard cells and mesophyll cells, but not in epidermal cells.

The space between the guard cells is called the stomata. Plants need to inhale and expel some gases in their lives, and the stomata are the "windows" for gas exchange between the leaves and the external environment. The opening and closing of the stomata is controlled by the guard cells.

2 The mesophyll is composed of palisade tissue and spongy tissue.

The mesophyll is composed of parenchyma cells containing many chloroplasts, which are generally clearly divided into two parts: palisade tissue and spongy tissue: the former is located under the upper epidermis, and the cells are cylindrical, and their length and diameter are arranged perpendicular to the epidermis, and the intercellular space is small; The latter is located between the palisade tissue and the lower epidermis, and the cells are irregularly shaped with large intercellular spaces, constituting a vast ventilatory system. Mesophyll cells contain chloroplasts, which are the main sites for photosynthesis in green plants.

Chloroplasts contain chlorophyll, so the leaves are green. Chlorophyll formation should be light. The mesophyll cells near the upper epidermis are cylindrical and neatly arranged, and the cells contain more chloroplasts. Mesophyll cells close to the lower epidermis have irregular shapes, loose arrangement, and less chloroplast content in the cells.

Because the palisade tissue cells are arranged neatly and closely, there are more chloroplasts. The palisade is organized close to the upper surface, so the top of the leaf is greener. The loosely arranged spongy tissue with few chloroplasts is close to the lower surface, so the underside (back) of the leaf is slightly lighter.

3 Leaf veins are the vascular bundles that grow on the leaves, and they are the branches of the vascular bundles in the stem.

Leaf veins are composed of a variety of cells, and the distribution of leaf veins in the mesophyll is like the "skeleton" of the leaf, so it can support the leaf to spread in the air to maintain normal life activities. It can be seen that the veins have a supporting effect on the leaves.

There are two kinds of pipes in the leaf veins: the conduit transports the water from the roots and stems and the inorganic salts dissolved in the water to all parts of the leaf to meet the needs of the leaf life, emphasizing the conduit to transport water and inorganic salts. The sieve tube in the leaf vein can send the organic matter made by the leaf out of the leaf, and then transport it to other parts of the plant body through the sieve tube in the stem, root and other organs.

The main veins in the leaf veins are composed of vascular bundles, which contain xylem and phloem, and between which there is often a cambium layer, but the cambium has a limited period of activity and produces only a small number of secondary structures. There are also many layers of mechanical tissue above and below the vascular bundles, among which the dorsal surface of the leaf is particularly developed, often forming significant protrusions. The veins of the leaves became thinner and thinner, the structure became simpler and simpler, the cambium layer disappeared, the mechanical organization gradually decreased or disappeared, and the xylem and phloem structures were also simple.

Although the morphology of the leaves is diverse, the basic composition is the same. It is composed of three parts: petioles, veins, and leaves. The leaves that all three parts have are called complete leaves, such as the leaves of peach trees, willows, moons, and other plants.

The leaf is composed of three parts: the blade, the petiole and the supporting leaf, and the three parts of the leaf, the petiole and the supporting leaf are called "complete leaves", such as the lack of petioles or supporting leaves are called "incomplete leaves".

1. a blade. Leaves are the most important components of leaves, mostly thin green flat bodies, this thin and flat form, with a large surface area, can shorten the distance between mesophyll cells and the leaf surface, and the leaf veins that play a supporting and conductive role are also in a network state. It is conducive to gas exchange and light energy absorption, the transport of water and nutrients and the output of photosynthetic products, and is a perfect adaptation to photosynthesis and transpiration.

2. a petiole. The petiole is the stalk-like part that follows the base of the leaf, and its lower end is connected to the branch. The main function of the petiole is to guide and support, the petiole can twist and grow, thereby changing the position and direction of the leaf, so that the leaves do not overlap each other, and can fully receive sunlight, this characteristic is called leaf mosaic.

3. Supporting leaves. The leaves are appendages at the base of the petiole and are often born in pairs. Its shape and function vary depending on the plant species, in addition to the protective effect on young leaves, some green leaves can also carry out photosynthesis.

The petiole mainly plays the role of connection, it is the connecting part between the leaf and the stem, if this part is disconnected, then the leaf has no connection with the main body, and it will die. The upper part of it is connected to the leaf, and the lower part is on the stem, and the petiole is generally located at the base of the leaf, which is an important component.

The leaf tray plays a great role in the leaf when it first grows, it is a small green membranous sheet that grows at the base of the petiole and on both sides, and generally grows out earlier, earlier than the time when the leaf grows, and can protect young leaves and small buds in the early growth stage. It is small in shape, but some of the blades are larger, and the corresponding leaf receptacles will also be large. Its growth is special because for some plants, it will fall off quickly as it grows and changes, while others will stay with it.

It is the most important part of the leaf, the epidermis is made up of a tightly packed layer of cells, and it has no color and is transparent. It contains chlorophyll, which can synthesize nutrients needed for plant growth by absorbing sunlight.

About the composition of the leaves is as follows:

It is one of the vegetative organs of vascular plants. Its function is to carry out photosynthesis to synthesize organic matter, and it has transpiration, providing the power for the root system to absorb water and mineral nutrients from the outside world.

Those with three parts: leaf, petiole and supporting leaf are called "complete leaves", such as missing petioles or supporting leaves are called "incomplete leaves"; It is divided into single leaf and compound leaf.

Leaves are the most environmentally sensitive organs in plants, and their morphological structure is the most likely to change with different ecological conditions to adapt to the environment. The leaves of different plants have a variety of forms, different sizes and different shapes. However, as far as a plant is concerned, it is relatively stable and can be used as a basis for identifying plants and taxonomic them.

At the same time, the leaf color is also diverse, generally speaking, the molecular ratio of chlorophyll to carotenoids in normal leaves is about 3:1, which makes the leaves appear green. In the cross-section, the structure of the leaf is composed of three parts: epidermis, mesophyll, and vein.

Leaves are generally composed of three parts: leaves, petioles and supporting leaves, such as the leaves of cotton, peach peas and other plants, and these three parts are called complete leaves. The leaves that lack any part or two of them are called incomplete whole leaves, such as sweet potato, rape, sunflower, etc., and the leaves lack supporting leaves;

The leaves of tobacco, lettuce, etc., lack petioles and supports; There are also some plants that have no leaves at all, only a flattened petiole on the stem, called a leaf-like stalk, such as the Taiwan acacia tree.

The composition of the leavesThe leaves of grasses are different from the leaves of general plants, and they are composed of two parts: the leaves and the leaf sheath. The leaves are linear or band-shaped, with longitudinal parallel veins. The leaf sheath is long and narrow and holds the stem, which has the role of protection, support and conduction.

Leaves are the most important components of leaves, mostly thin green flat bodies, this thin and flat form, with a large surface area, can shorten the distance between mesophyll cells and the leaf surface, and the leaf veins that play a supporting and conductive role are also in a network state.

These characteristics are conducive to gas exchange and absorption of light high and high energy, the transport of water and nutrients and the output of photosynthetic products, and are perfect adaptation to photosynthesis and transpiration.

Leaves are generally composed of three parts: the leaf, the petiole and the supporting leaf.

The leaf is composed of three parts: epidermis, mesophyll and vein. The petiole is the part that connects the leaf and the stem, the upper end is connected to the leaf, and the lower end is connected to the stem. The leaves are born at the junction of the petiole and the stem, respectively on both sides, and its form and function vary according to the plant.

Photosynthesis of leaves:

Leaves can photosynthesize, and plants have small green particles in their leaves called chloroplasts. It has a special power capable of photosynthesis, making food for itself. Leaves can undergo transpiration, and the taller part of the plant cannot obtain water without the pulling force of transpiration to absorb water and transport water in the body. The leaves can perform respiration, and the stomata on the leaves resemble the nostrils and mouth of animals, and air can enter and exit through the stomata. The inhaled gas can diffuse to all parts of the tree to meet the needs of growth.