Plant Physiology: IV. Plant Reproduction

Why Anthers are Best:

• Easily Accessible: Anthers are readily accessible for dissection and observation.
• Synchronous Meiosis: Meiosis in anthers often occurs in a synchronous manner, making it easier to observe the stages of meiosis at the same time in multiple cells.
• Large Number of Cells: Anthers contain a large number of microspore mother cells, increasing the likelihood of finding cells at different stages of meiosis

Viruses are transmitted from plant to plant in a number of ways such as vegetative propagation. Viral diseases could be transferred through vegetative parts. So the statement 2 is incorrect. Vegetative propagation can be practised most of the year. Hence, statement 3 is correct.

Gootee in plants is a method of vegetative propagation of plants that requires the rooting of aerial stems when connected to the parent plant. It is also named as air layering, marcotting, pot layerage, marcottage and circumposition.

This refers to asexual reproduction in plants, where new plants are produced from vegetative parts like stems, leaves, or roots, rather than seeds. In this specific method, a section of the aerial stem of a plant is manipulated to encourage root formation while still connected to the parent plant.

The stem is girdled (a ring of bark is removed) or otherwise altered to interrupt nutrient flow, stimulating the production of roots in the exposed area. A rooting medium, like sphagnum moss, is then applied around the girdled area to provide moisture and support.

The parent plant continues to provide nutrients and water to the developing roots until they are well-established. Once sufficient roots have formed, the new plant can be carefully separated from the parent plant and grown independently.

• The 'bud chip' method for cane plantation reduces the mass and enables quick multiplication of seeds. This method has proved to be more economical and convenient than the traditional way of planting two or three bud sets.
• The returns are relatively better and a substantial saving in seed material is made when 'bud chip settlings' are raised in a nursery and transplanted in the main field.
• When direct planting of setts is done, it is found that the germination percentage is better with many-buds setts as compared to single-budded setts.
• When setts are directly planted, large setts have better survival under bad weather than single-budded setts.
• Planting material for vegetative propagation of sugarcane includes whole cane, setts having of single buds to many buds, setts prepared in nursery or setts prepared from tissue culture.
  Hence, among the given statements, only statements 1 and 4 are correct.

An effective crop rotation system requires right selection of crops that adjust well with the space, sunlight and soil in rooftop garden. General principles that guide crop rotation are listed hereafter :

• Leguminous crops should be followed by non-leguminous crops.
• The crops with tap roots (dicots) should be grown after those which have fibrous root system (monocots).
• Slow-growing crops which are more vulnerable to weeds should be grown immediately after weed-suppressing crops in a rotation system.
• Closely related species should not be grown successively as they act as alternate hosts for insects, pests and diseases.
• Deep rooted crops should be succeeded by shallow rooted crops.
• Crops susceptible to soil borne pathogens and parasitic weeds should be followed by tolerant crops.

Intercropping is the practice of growing two or more crops in proximity. Pulses are generally intercropped with coarse cereals and oilseeds under rainfed condition in our country.

Pulses, when included in intercropping with cereals, act as complimentary crops. The slow initial growth habit and deep tap root system makes these crops more suitable for intercropping with cereals and oilseed crops than any other crop.

Pulses with tap root system, do not compete for nutrients and moisture with cereals having fibrous root system. The tap root system allows plants to anchor better, get sources of minerals and water from further into the ground than fibrous-rooted plants.

Apart from increasing profitability and resource use efficiency, pulses as intercrop act as safeguard under unprecedented moisture stress condition. Pulses can contribute significantly to achieve the twin objectives of increasing productivity and improving the sustainability of rice and wheat based cropping systems.

The pulses grown together with or before a cereal crop can reduce and sometimes substitute the need of nitrogen application as well. Hence, both (A) and (R) are true but (R) is not the correct explanation of (A).

These artificial process of producing plantlet involves 5 different methods:

• Meristem Culture
  In this method of micropropagation, subtending leaf primordial and a meristem is placed into their respective growing media culture and allowed to grow. After some weeks, an elongated rooted plantlet is produced. Once after they reach a considerable height, these plantlets are transferred into the soil. In this method, a disease-free plant can be produced and can be successfully used for rapid multiplication of various herbaceous plants.
  
• Callus Culture
  In this method, selected plant tissue is placed in an artificial growing medium culture until the callus is formed. After the production of callus, they are transferred into a culture medium containing plant growth regulators for the induction of adventitious organs. After a few weeks, a new plantlet is exposed gradually to the environmental condition.
• Suspension Culture
  In this method of micropropagation, cells or groups of cells are dispersed and allowed to grow in an aerated and sterile liquid culture medium.
  
• Embryo Culture
  In the method of embryo culture, the embryo is extracted and placed into a culture medium with proper nutrient in aseptic condition.
  
• Protoplast Culture
  In this method, the plant cell is isolated and cultured in an appropriate medium to reform the cell wall and callus. Later, under suitable conditions, the cell develops a cell wall followed by an increase in cell division and cellular differentiation and grows into a new plant.
  

In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem.

Buds are formed from meristematic tissue, the plant's actively dividing cells. They can be axillary (at the leaf axil), terminal (at the tip of a stem), or lateral (on the sides of stems). Buds have the potential to develop into new shoots, leaves, or flowers.

Buds can be classified as vegetative (producing leaves and stems) or reproductive (producing flowers and/or fruits).

Many buds remain dormant during unfavorable conditions (e.g., winter) and become active when conditions are more suitable. The shoot tip (terminal bud) generally inhibits the growth of axillary buds, a phenomenon called apical dominance.

The embryo develops into a new plant after germination, where the seed absorbs water and other nutrients, causing the embryo to start growing into a seedling. The seed is formed after fertilization, where the embryo, along with other cells from the mother plant, develops inside the seed.

The seed contains the embryo, which is essentially the baby plant. The seed also contains nutrients stored in the endosperm, which provides the embryo with nourishment during germination.

Germination is the process of the seed sprouting and developing into a seedling. It requires conditions like water, oxygen, and optimal temperature.

When the seed absorbs water, it swells and softens, allowing the embryo to start growing. The embryo begins to emerge from the seed coat, with the radicle (embryonic root) emerging first.

After the radicle, the plumule (embryonic shoot) develops and emerges above the soil. The radicle develops into the root system, anchoring the plant and absorbing nutrients.

The plumule develops into the stem and leaves of the new plant. The cotyledons (seed leaves) provide nourishment to the developing seedling, especially in dicots (plants with two cotyledons).