why do the vegetative parts of some plants get modiefied
Answers
Answer:
because of the germination of plant it means growing of plant
Vegetative Plant Parts
External plant structures such as leaves, stems, roots, flowers, fruits, and seeds are known as plant organs. Each organ is an organized group of tissues that works together to perform a specific function. These structures can be divided into two groups: sexual reproductive and vegetative. Vegetative parts (Figure 1) include roots, stems, shoot buds, and leaves; they are not directly involved in sexual reproduction. Vegetative parts often are used in asexual forms of reproduction such as cuttings, budding, or grafting.
Roots
Often roots are overlooked, probably because they are less visible than the rest of the plant. However, it's important to understand plant root systems because they have a pronounced effect on a plant's size and vigor, method of propagation, adaptation to soil types, and response to cultural practices and irrigation.
Roots typically originate from the lower portion of a plant or cutting. They have a root cap, but lack nodes and never bear leaves or flowers directly. Their principal functions are to absorb nutrients and moisture, anchor the plant in the soil, support the stem, and store food. In some plants, they can be used for propagation.
Structure
Internally, there are three major parts of a root (Figure 2):
The meristem is at the tip and manufactures new cells; it is an area of cell division and growth.
Behind the meristem is the zone of elongation. In this area, cells increase in size through food and water absorption. As they grow, they push the root through the soil.
The zone of maturation is directly beneath the stem. Here, cells become specific tissues such as epidermis, cortex, or vascular tissue.
A root's epidermis is its outermost layer of cells (Figure 3). These cells are responsible for absorbing water and minerals dissolved in water. Cortex cells are involved in moving water from the epidermis to the vascular tissue (xylem and phloem) and in storing food. Vascular tissue is located in the center of the root and conducts food and water.
Externally, there are two areas of importance: the root cap and the root hairs (Figure 2). The root cap is the root's outermost tip. It consists of cells that are sloughed off as the root grows through the soil. Its function is to protect the root meristem.
Root hairs are delicate, elongated epidermal cells that occur in a small zone just behind the root's growing tip. They generally appear as fine down to the naked eye. Their function is to increase the root's surface area and absorptive capacity. Root hairs usually live 1 or 2 days. When a plant is transplanted, they are easily torn off or may dry out in the sun.
Many roots have a naturally occurring symbiotic (mutually beneficial) relationship with certain fungi, which improves the plant's ability to absorb water and nutrients. This beneficial association is called mycorrhizae (fungus + root).
Types of roots
There are two major types of roots: primary and lateral. A primary root originates at the lower end of a seedling's embryo. If the primary root continues to elongate downward, becomes the central feature of the root system, and has limited secondary branching, it is called a taproot (Figure 4). Hickory and pecan trees, as well as carrots, have taproots.
A lateral, or secondary, root is a side or branch root that arises from another root. If the primary root ceases to elongate, and numerous lateral roots develop, a fibrous root system is formed. These lateral roots branch repeatedly to form the network of feeding roots found on most plants.
Some plants, such as grasses, naturally produce a fibrous root system. In other cases, severing a plant's taproot by undercutting it can encourage the plant to produce a fibrous root system. Nurseries use this technique with trees that naturally produce a taproot because trees with a compact, fibrous root system are transplanted more successfully.