Dwarfness can be controlled by treating the plant with [1992, 2002]
One of the most important effects of gibberellins is the reversal of dwarfism (even in genetically dwarf plants). Dwarf pea & dwarf corn attain almost normal size when treated with gibberellins. It has been proved that dwarf plants have lower level of GA which causes the dwarfism. Thus the external supply causes rapid elongation of internodes. GA does not have any effect of elongation on normal (non dwarf or tall) plant.
Klinostat is employed in the study of 
Klinostat = Clinostat is an apparatus used to nullify the effect of geotropism. It has a clock to the main axis of which is attached to a rod. Top of the rod is attached to a flower pot. The klinostat is kept in horizontal position and allowed to rotate (to nullify the geotropism) and plant growth is observed
What is a stress hormone? or The hormone produced during adverse environmental conditions is 
Abscisic Acid (ABA) is called stress hormone which works in adverse environmental condition when there is low water content in atmosphere or in drought conditions. ABA causes the stomatal closure of leaves due to which the water loss by the plant is minimized.
The regulator which retards ageing/ senescence of plant parts is : 
Cytokinin help in retaining chlorophyll, hence delay senescense.
Removal of apical bud results in [1993, 2000]
Apical buds inhibit lateral branching due to apical dominance. Removal of apical bud promotes lateral branching.
Movement of auxin is 
Auxin is a plant hormone which is involved in various physiological processes of plant. It is synthesized in meristematic tissue like tip of root and stem. In stems, movement of auxin is basipetal. It moves from apex to the base. However, in roots, movement of auxin is acropetal. It moves from the root to the shoot apex.
Thus, the correct answer is option D.
The pigment, that absorbs red and far red light in plants, is [1995, 97, 2002]
The pigment phytochrome is involved in flowering and many other light-mediated processes. It absorbs red and far red light in plants for photosynthesis.
Ethylene gas is used for 
Ethylene is a gaseous plant hormone which plays an important role in fruit ripening. In the presence of ethylene there is an increase in the rate of respiration.
Thigmotropic movement is best shown by
The phenomenon of thigmotropism is a response to contact with a solid object. It is exhibited by tendrils of climbing plants that grow around a pole or the stem of another plant.
What will be the effect on phytochrome in a plant subjected to continuous red light? 
Continuous exposure to red light causes
If a tree, flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be 
In northern India, during these months there is observed maximum variation in light intensity and duration and temperature. Hence only plants that are photo-and thermoinsensitive can flower during these months.
Which combination of gases is suitable for fruit ripening? 
Ethylene acts physiologically as a hormone in plants. It stimulates the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves. Its biosynthesis starts from methionine with 1-aminocyclopropane-1-carboxylic acid (ACC) as a key intermediate.
A plant hormone used for inducing morphogenesis in plant tissue culture is 
Cytokinins are used in tissue culture to induce shooting of the cultural callus.
The response of different organisms to environmental rhythms of light and darkness is called 
Photoperiodism is the effect of duration of light and darkness on the growth, development and behaviour of an organism.
ABA is involved in 
Gibberellins are involved in shoot elongation. Auxins are important in root elongation and cell division
The method that renders the seed coat permeable to water so that embryo expansion is not physically retarded is 
Scarification is the breaking of the seed coat barriers which can be done by mechanical or chemical methods.
What reason will you assign for coconut milk used in tissue culture? [2000, 03]
The medium in tissue culture provides all the essential nutrients required for growth and division of callus. Coconut milk contains cytokinins which is useful in tissue culture.
Geocarpic fruits are produced by [2000, 02]
Geocarpic fruits are those which develop underground. Groundnut is the fruit which develops underground, onion and carrot also occur within the soil but onion is modified stem while carrot is modified root.
What breaks bud dormancy of potato tuber?
IAA promotes apical dominance. ABA induces dormancy in buds.
Hormone responsible for senescence 
ABA or Abscisic acid is responsible for leaf fall or senescence.
Which of the following prevents fall of fruits?
NAA or Naphthalene Acetic Acid is synthetic auxin. It is used to check fruit fall specially in tomato.
Which one is a long-day plant? 
Long day plants undergo flowering after receiving light above a critical day length. e.g. Spinach, sugarbeet. Short day plants flower only when they receive light below a critical day length. e.g. Glycine max, Tobacco.
Glycolate induces opening of stomata in 
During day time, due to photosynthesis CO2 concentration is low.
Proteinaceous pigment which control activities concerned with light 
Seed dormancy is due to the 
Ethylene breaks dormancy of different plants. Abscisic acid induces dormancy in seeds, buds and underground storage organs