Root metamorphosis: The roots of some plants have undergone great changes in morphology, structure and physiological functions. This change is called metamorphosis. Metamorphosis is the result of long-term adaptation to the environment. After this trait is formed, it will be inherited one after another and become a stable genetic trait.
Fleshy roots, such as deformed roots of radish, carrot and beet. They are formed by the swelling of the taproot and the upper end of hypocotyl. In the hypertrophic taproot, parenchyma cells store a lot of nutrients, which can be used for the overwintering and growth of plants in the following year. This part is also edible.
Pillar root: The most typical example is corn. Many adventitious roots grow from several nodes at the base of the stem and extend downward into the soil, which not only absorbs water and inorganic salts, but also has developed mechanical tissues, which can play a supporting role in stabilizing the stem. Ivy, Camptotheca acuminata and other plants have numerous adventitious roots on their slender stems, which are used to fix themselves on walls or other plant stems. This abnormal root is called climbing root. Parasitic angiosperms, such as Cuscuta Cuscuta, have their stems wrapped around the host's stems, producing many haustoria, which extend into the internal tissues of the host's stems, and their vascular tissues are connected with those of the host, thus absorbing the water and nutrients of the host.
Mycorrhiza and nodule: The roots of many plants have established a biological relationship with microorganisms in the soil, forming mycorrhiza or nodule on plants. The * * * living body formed by the roots of some seed plants and soil fungi is called mycorrhiza. According to the infection of fungi on host cortical cells, it can be divided into two types:? Ectomycorrhiza, fungi form a sheath, that is, mycelium cover, which completely wraps the outside of young roots, and only a few hyphae invade the intercellular space of root cortex, such as pine and oak. Endophytic mycorrhiza, fungi form an inconspicuous cover, and most hyphae invade cells in the root cortex, such as orchids and strawberries. The mycelium of mycorrhizal fungi, like root hair, plays the role of absorbing water and mineral nutrients. It can also transform mineral salts and organic matter in the soil into nutrients easily absorbed by the host and make vitamins for the roots. However, organic substances such as sugars and amino acids secreted by host plants can be used for fungi to survive, so they are related. The living organisms of leguminous plants and rhizobia are nodules. The vascular bundles of nodules are connected with the vascular columns of roots, which can supply nutrients to each other. On the one hand, leguminous plants provide water and nutrients for the growth of rhizobia; On the other hand, rhizobia also transport fixed synthetic ammonium nitrogen to host plants through transport tissues.
Aerial roots are deformed roots that grow in the air. For example, many adventitious roots grow on the branches of banyan trees and can hang down to the soil. This aerial root has no root hair and root cap, and can't absorb nutrients, but it can absorb water in the air and also has the function of breathing. Because aerial roots are rooted in the soil and play a supporting role, the crown of banyan trees can be developed, so there is a feeling of "standing alone into a forest". Orchids in many tropical forests also have developed aerial roots, which can be divided into respiratory roots, columnar roots, climbing roots and haustorium because of their different functions.
Lateral roots or adventitious roots of tuber plants swell. Unlike radish, this deformed root only forms a fleshy root, but a plant can form many swollen tuberous roots. Common sweet potato tubers.
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