Plants are one of the five kingdoms of living organisms on our planet. They belong to eukaryotes, that is, creatures whose cells contain a nucleus.
Plant structure
They can be either unicellular or multicellular. The second are divided into such departments as green, brown and red algae, spore, gymnosperms and angiosperms. The organism of algae can consist of both one cell and many, but there are no organs in their structure, the solid body is called thallus. In spore, gymnosperms and angiosperms (flowering), the presence of differentiated tissues and organs is observed. The latter are divided into vegetative and generative.
The first includes shoot (stem and leaves), as well as the root. Many are interested in the question: “Why are the leaves green?” Why such a color? Also, many children ask the question: “Why are the leaves green?” And this article we will begin with this topic.
Why are the leaves green?
This color is due to the presence of chlorophyll. In the fall, this pigment is lost, and the green leaf turns into red, orange or yellow. Why is this substance needed? It is simply vital for the plant. Without it, the process of photosynthesis cannot occur, due to which nutrients are produced. Organic plant chemicals are usually obtained only as a result of this process. However, some species living in the lower layers of the rainforests do not receive enough light for full photosynthesis; therefore, they resort to hunting for small insects, thus compensating for the lack of organic compounds. These include sundew, slipper venus, etc.
Briefly about the structure of the plant cell
It consists of a plasma membrane, a cell wall of cellulose, a cytoplasm in which organoids are contained, and a nucleus in which DNA is located. The following organelles are contained in the cytoplasm: mitochondria, ribosomes, endoplasmic reticulum, vacuole (in the old cell - one large, in the young - several small), Golgi complex and plastids (chloroplasts, leukoplasts, chromoplasts).
Each of them performs its
functions. Mitochondria produce energy, ribosomes synthesize proteins, the endoplasmic reticulum (reticulum) produces lipids, vacuoles accumulate unnecessary substances, because it is impossible to bring them out due to a solid cell wall, photosynthesis takes place in chloroplasts, chromoplasts contain pigments, leukoplasts store reserve nutrients ( basically it's starch).
How does photosynthesis occur?
This process is carried out in chloroplasts, which are in the cytoplasm of the cell. These organelles are single-membrane, their structure includes thylakoids - thin plates collected in granules - piles. It is in them that chlorophyll is contained - that is why the leaves are green. In addition, chloroplasts contain ribosomes involved in the production of proteins, starch grains, as well as ring DNA molecules that record information about substances that must be synthesized in the cell.
In the process of
photosynthesis, plants absorb solar energy, water and carbon dioxide, and produce oxygen as a by-product of the reactions. Enzymes that help carry out chemical interactions are located directly in the chloroplast matrix (the substance that fills it).
What are the leaves made of?
Several types of plant tissue can be found in this organ ; there are four of them. These are the epidermis, mesophyll, conductive tissues (xylem and phloem), as well as mechanical tissues. Photosynthesis proceeds precisely in the mesophyll, or parenchyma. You can see green leaf cells under a microscope. This is the upper ball - the epidermis.
Its cells are located closely to each other, but in this layer there are pores that allow you to absorb carbon dioxide and release oxygen, as well as regulate the water and temperature balance. The parenchyma (mesophyll) is divided into two layers - one of the columnar cells, the other of the spongy cells. The first contains more chloroplasts than the second. The xylem is represented by vessels through which the fluid is delivered from the roots to the leaves, that is, up, and the phloem consists of sieve-like tubes through which water is transported down. Mechanical fabrics provide the sheet stiffness and stability, a certain shape.