Plant Biology and Agriculture

It is a bacterium which lives in the root nodules of leguminous plants like pea and helps in fixing atmospheric nitrogen.

Magnesium is the metallic element present in the chloroplast of plants.

After a crop is harvested, the grains are separated from the chaff by a process called threshing.

Chromoplast imparts colour to flower and fruits. So, they help in pollination and fruit dispersal.

After harvesting and before raising the next crop, the field lies bare. The wind blows off the top soil at that time. Thus, to prevent the soil from being blown away, the farmers grow cover crops such as grass and creepers.

Petal attracts insects for pollination.

Stomata are microscopic pores primarily found on leaf surfaces that serve two critical functions: gas exchange (CO2 intake for photosynthesis, O2 release) and transpiration (water vapor loss). Option B describes xylem function, and option C describes phloem function. Stomata open and close via guard cells to balance these processes.

Thigmotropism (from Greek 'thigma' meaning touch) is the directional growth movement in response to physical contact or touch. The classic example is the coiling of tendrils around supports. Geotropism is gravity response, hydrotropism is water response, and plagiotropism is growth at an oblique angle to gravity.

Cutting is a vegetative propagation method where a stem piece is placed in soil to grow roots. This technique is widely used for roses because it's simple and preserves the parent plant's characteristics. Grafting is also common but requires more skill, while tissue culture is mainly for commercial-scale production.

Young trees are often grown as houseplants in areas where the winters are too cold for them to grow outside (they will not, for example, survive outdoors in most of the areas of the United States or Europe), and are sometimes used as Christmas trees.

Chloroplast is known as the 'kitchen of the cell' because it is responsible for the preparation of food by photosynthesis.

Clove, the commonly used spice, is obtained from the flower bud.

Auxin, gibberellin, abscisic acid, and cytokinins are the five major plant hormones that regulate growth and development. Ascorbic acid (Vitamin C) is an antioxidant and enzyme cofactor in plants, but it does not function as a growth hormone like the others.