The different groups of plants differ greatly in structure.
Inferior plants have no organs or tissues. Algae belong to this group of plants. Their body is called the taproot, or thallus. The cells of the phloem in most cases have the same structure. The lack of cell specialization to perform certain functions – photosynthesis, absorption and carrying out of solutions, providing body strength – is due to the algae living in water. All or most of the cells of these plants are in the light and are capable of photosynthesis. In an aquatic environment, lower plants obtain nutrients by absorbing them with their entire body surface. Therefore, they have no need for rapid movement of substances through the body, and thus no need for a conductive system. Water density is high enough and lower plants do not have to hold their bodies upright and resist gravity, so they do not have developed mechanical tissues.
Higher plants have functionally different organs formed by specialized cells. Higher plants include mosses and vascular plants – fern-like plants, clavate plants, holosperms, and angiosperms.
Most of the higher plants live on land. They obtain water and mineral nutrition from the soil and must rise above the soil surface to carry out photosynthesis. Therefore, higher plants have developed tissues responsible for the movement of substances between parts of the organism (conductive tissue) and for the strength and support of the terrestrial part (mechanical and covering tissues).
The presence of specialized cells, tissues, and organs allowed higher plants to reach large sizes and master all habitats. Many representatives of higher plants have reverted to water. On land and in freshwater reservoirs, they make up the bulk of the vegetation.
Plant life forms
A life form is the external aspect of a plant. Plants have four main life forms: trees, shrubs, bushes, and grasses.
A tree is a perennial plant with one large, woody trunk. Examples: spruce, apple tree, oak, palm tree.
A shrub is a plant with multiple, small, woody trunks, and usually does not live more than 10-20 years. Examples: hawthorns, snowballs, currants, raspberries.
Shrub – a low-growing perennial plant with single, woody trunks, up to 40 cm in height. Examples: blueberries, cranberries, heather.
Grasses, or herbaceous plants, are plants with green above-ground shoots that die off annually. Grasses can be annual (e.g., cornflower, chamomile), biennial (carrots, cabbage), and perennial (dandelion, clover). Biennial and perennial grasses have new shoots growing out of their wintering buds in the spring.