Tag: botany

Guttation is the excretion of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses. In the absence of light, plant loose excess water in the form of liquid through hydathodes because most plants have their stomata closed at night. When there is a high soil moisture level, water will enter plant roots, because the water potential of the roots is lower than in the soil solution. The water will accumulate in the plant, creating a slight root pressure. The root pressure forces some water to exude through special leaf tip or edge structures, hydathodes or water glands, forming drops. Therefore, the correct answer is option A.

Guttation is the term used to refer to the phenomenon in which droplets of eater secreted from the pores in leaves of plants. It occurs through specialised pores called hydathodes. It takes place at night and in conditions of high root pressure and low transpiration. It occurs in plants growing under conditions of high soil moisture and high humidity. Thus, the correct answer is 'It occurs through specialised pores called hydathodes.'

The agriculture sector of India employs about 70 percent of the population, in which 80% are rural population. The agriculture share in the GDP of India is 20.5 %.

Horticulture has been defined as the agriculture of plants, mainly for food, materials, comfort and beauty. According to American horticulturist Liberty Hyde Bailey, "Horticulture is the growing of flowers, fruits and vegetables, and of plants for ornament and fancy." Hence, vegetable crop cultivation is known as Horticulture.

Wide hybridization can be used to transfer the desirable variability. It is used for producing haploids, diploids from tetraploids and trihaploids from hexaploids.

A. G.J Mendal is known for his discovery of fundamental laws of inheritance.

Totipotency - The ability of cells such as an embryonic stem cell to differentiate into any type of body cell. Plant cells are also totipotent, which helps to explain why a graft of a plant can generate a whole new individual out of just a small branch cutting.
Totipotent cells can form all the cell types in a body, plus the extraembryonic, or placental, cells. Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are totipotent. Pluripotent cells can give rise to all of the cell types that make up the body; embryonic stem cells are considered pluripotent. Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells; adult stem cells and cord blood stem cells are considered multipotent.

The Rht-B1b and Rht-D1b dwarfing genes were derived from Norin-10, which was a semi-dwarf variety bred in Japan and released in 1935 (Gale and Youssefian, 1985). Norin-10 was used in US breeding programs in the 1950s in order to improve lodging resistance in winter wheat, in which lodging was a serious problem when high rates of nitrogen fertilizers were applied. A selection from a cross of Norin-10 with the US variety, Brevor was particularly promising and was used by Borlaug in the development of the green revolution wheat varieties. Wheat Norin-10 is a semi-dwarf wheat cultivar with very large ears that was bred at an experimental station in Iwate Prefecture, Japan. Norin-10 helped developing countries, such as India and Pakistan, to increase the productivity of their crops from approximately 60% during the green revolution. Thus, the correct answer is option B.

A crescograph is a device for measuring growth in plants. It was invented in the early 20th century by Sir Jagadish Chandra Bose. The Bose crescograph uses a series of clockwork gears and a smoked glass plate to record the movement of the tip of a plant (or its roots) at magnifications of up to 10,000. Marks are made on the plate at intervals of a few seconds, demonstrating how the rate of growth varies under varying stimuli. Bose experimented with temperature, chemicals, gases and electricity.