Plant Pathology - Study Mode
[#581] Cryoprotectant should be added to spores
Correct Answer
(B) Before storing in liquid nitrogen
Explanation
Solution: Cryoprotectants should be added to spores before storing them in liquid nitrogen. A cryoprotectant is a substance used to protect biological tissue from freezing damage. Cryoprotectants are also used to preserve living materials in the study of biology and to preserve food products. For years, glycerol has been used in cryobiology as a cryoprotectant for blood cells and bull sperm, allowing storage in liquid nitrogen at temperatures around -196°C.
[#582] A complex mixture of brown or dark brown amorphous and colloidal substances modified from the original tissues or synthesised by various soil organisms is referred as
Correct Answer
(D) Humus
Explanation
Solution: A complex mixture of brown or dark brown amorphous and colloidal substances modified from the original tissues or synthesized by various soil organisms is referred to as Humus. Humus is a complex rather resistant mixture of brown or dark brown, amorphous and colloidal substances modified from the original tissues or synthesized by the various soil organisms. It is a colloidal substance and increases the cation-exchange capacity of the soil, hence its ability to store nutrients by chelation. While these nutrient cations are available to plants, they are held in the soil and prevented from being leached by rain or irrigation.
[#583] Plant deficient in zinc, show reduced biosynthesis of growth hormone
Correct Answer
(B) Auxin
Explanation
Solution: Plants deficient in zinc, show reduced biosynthesis of the growth hormone Auxin. Plants also require zinc for the synthesis of tryptophan, a key amino acid in the synthesis of the auxin indoleacetic acid. Therefore, zinc also operates in the control of plant development through its indirect action on auxins.
[#584] In photosynthesis, oxygen is liberated during
Correct Answer
(D) Hydrolysis of water
Explanation
Solution: In photosynthesis, oxygen is liberated during Hydrolysis of water. Two water molecules are oxidized by the energy of four successive charge-separation reactions of photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions. The electrons yielded are transferred to a redox-active tyrosine residue that is oxidized by the energy of P680 + . In light, the electron acceptor is reduced and oxygen is evolved.
[#585] Loose smut is
Correct Answer
(A) Internally seed borne
Explanation
Solution: Loose smut is internally seed borne. Loose smut of barley is caused by Ustilago nuda. It is a disease that can destroy a large proportion of a barley crop. Loose smut replaces grain heads with smut, or masses of spores that infect the open flowers of healthy plants and grow into the seed. The major symptom of loose smut is the "smutted" grain heads, which contain masses of black or brown spores. The most widely used method of control for loose smut is using treated seed. Seeds are typically treated with a systemic fungicide to kill any fungus that may be inside.