Plant Biology Roots, stems structure problems

The vascular bundles of sunflower stems are cylindrical, and the vascular bundles of corn stems are scattered and arranged.

The mechanism is different, and the longitudinal growth is because of auxin.

The transverse thickening is due to the cambium growing inward as xylem and outward as phloem.

In drought conditions, the straight root system is more advantageous, and the fibrous root system of aquatic plants is dominant.

There is no cuticle.

The roots absorb water and inorganic salts.

The part is mainly the root hairs. The cell wall of the root hair is very thin, the cytoplasm is close to the cell wall to form a thin layer, and the ** of the cell is a large vacuole, which is filled with cell sap. This structure is suitable for absorbing moisture.

The primary structure of the roots and stems of dicots is composed of three parts: epidermis, cortex, vascular tank. The epidermis is a protoepidermis that develops, usually a layer of long cells. The root epidermal cells have thin-walled, thin cuticles, do not have pores, and form root hairs; The epidermis is close to the cell wall, exposed to air in the tangential wall of the stem cell protoplasts are thicker than the other, and keratinocytes, stratum corneum, porosity.

The cells of the root cortex are often gapless, and the Kjeldahl belt thickens the endothelium to form compact; The outer ** near the stem thickens, forming one or more layers of cells with thick horns, and the stem endothelial layer of most plants is inconspicuous. The root column sheath of the vascular cylinder alternates primary xylem, phloem, parenchyma cells, and primary xylem development mode initiation type outside; The trunk vascular tube consists of vascular bundles, medulla, medullary rays, a relative arrangement of vascular bundles of primary xylem and phloem, and the development of primary xylem is the appearance of the initial style of early type primary phloem development.

The vascular bundles of sunflower stems are cylindrical, and the vascular bundles of corn stems are scattered and arranged.

It's the part of the hypocotyl that develops.

The part of the plant body that connects the root and the stem is the hypocotyl; The hypocotyl is the part that connects the root to the stem. The seed coat is the "armor" of the seed and plays the role of protecting the seed. The embryo is the most important part of the seed and can develop into the roots, stems, and leaves of the plant.

The endosperm is where the seeds concentrate their nutrients, and the nutrients contained in the endosperm of different plants vary.

The seed coat is the "armor" of the seed and plays a role in protecting the seed.

What morphology, structure and function of plant leaves are compatible with the leaf Leaf is a vegetative organ that grows on the stem of a plant and is responsible for making nutrients. Every leaf is a small green chemical factory. In the leaves there is something called chlorophyll, which is the "worker" of the leaf chemical plant, chlorophyll uses sunlight, carbon dioxide in the air and sucks from the roots.

1 Similarities: They are all composed of three parts: epidermis, cortex and vascular column, and the cell types of each part are basically the same in roots and stems, and the development sequence of primary phloem in roots and stems is exogenous. 2 The differences are:

l) The root epidermis has root hairs and no stomatae, and the stem epidermis has no root hairs and often has stomata. (2) There is an endothelial layer in the root, the cells in the endothelial layer have a Kjeldahl band, and the vascular column has a middle column sheath; However, most dicots do not have a significant endothelial layer in the stem, although they do not have a Kjeldahl zone, and the stem vascular column does not have a mesocolumella sheath. (3) The primary xylem and primary phloem in the root were arranged alternately in bundles, while the primary xylem and primary phloem in the stem were arranged side by side inside and outside to form a bundle-like structure.

4) The development order of the primary xylem in the root is the outer initiation form, while the development sequence of the primary xylem in the stem is the inner initiation form. (5) There are no parrow rays in the roots, and some dicot plants have no parrow in their roots, and the stems are marrow, and there are marrow rays between the vascular bundles. These differences are determined by the functions performed by the two and the environmental conditions in which they are located.