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Bananas can be prevented from over-ripening by
Ascorbic acid is an organic acid with antioxidant properties. Its appearance is white to light yellow crystals or powder. It is water soluble. The L-enantiomer of ascorbic acid is commonly known as Vitamin C. Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions and as a preservative.
Flowering dependent on cold treatment is 
Vernalization is the method of inducing early flowering in plants by pretreatment of their seeds at low temperature.
Apical dominance is caused by 
Apical dominance is the phenomenon by which presence of apical bud does not allow lateral buds to grow. Apical dominance is due to auxin. When shoot tip is cut; then lateral buds start growing.
In short day plants, flowering is induced by
A short day plant is one that flowers on photoperiods shorter than the critical day length. It generally flowers when treated by a short day and uninterrupted long night (more than 12 hrs.)
Cytokinins cause delay in senescence (Richmond-Lang effect). Senescence is the phenomenon in which the mature leaves lose chlorophyll, turn yellow and fall off.
Which is employed for artificial ripening of banana fruits? [1992, 2000]
Ethylene is a plant hormone which has the most remarkable effect of stimulation of fruit ripening.
Abscisic acid causes 
Abscisic acid is a stress hormone. During desication abscisic acid is synthesized which reduces transpiration by closure of stomata. It conserves water.
The hormone responsible for a pical dominance is 
Apical dominance is caused by the action of auxins & IAA (Indole-3-acetic acid) is a naturally occurring auxin.
A chemical believed to be involved in flowering is [1991, 95]
Chailakhyan (1936) a Russian investigator who researched on photoperiodism proposed the term ‘florigen’. According to him ‘Florigen Complex’, the true flowering hormone includes two group of substances formed in leaves (i) Gibberellins which are necessary for the formation and growth of stem and (ii) Anthesins which are necessary for flower formation. Acting together they form the substance named ‘florigen’
Tendrils exhibit/twining of tendrils is due to 
Twining of tendrils is due to thigmotropism i.e. movement due to the contact with a foreign body (touch).
Highest auxin concentration occurs 
Highest concentration of auxins occurs at the growing tips was proved by Went in 1928 by his experiment on Avena coleoptile. It was demonstrated that auxins are synthesized at the tips and then translocated downwards where they cause growth.
Phytohormones are : 
Phytohormones are plant hormones which are synthesized by the plants and act as regulators and influence physiological process like growth, movements etc. auxins, gibberellins etc. are the phytohormones.
Abscisic acid controls 
Abscisic acid as the name suggests cause abscission due to which leaves fall. It also acts as a growth inhibitor & induce bud dormancy in various plants.
Phototropic and geotropic movements are linked to : 
Phototropic movements are the plant responses towards light. Generally plant shoot and flower show positive phototropism while geotropism is the plant response to the gravity of earth. Generally roots are positively geotropic. All these movements are linked to Auxin.
Which of the following movement is not related to auxin level 
All except nyctinastic movement are related to auxin. Nyctinastic (sleeping) movement of leaves are due to diurnal changes. (changes in day and night).
Which of the following hormones can replace vernalisation? 
Vernalization is the low temperature treatment for flowering in plants. Plants are treated (seeds and seedlings) with very low temperature to promote germination. A Lang & co-workers demonstrated that the application of gibberellins can replace the cold treatment or vernalization in many plants.
Leaf fall can be prevented with the help of
It is due to Richmond-Lang effect. Cytokinins prevent degeneration of chlorophyll, proteins and nucleic acids. They increase of inflow of auxin and amino acids. It reactivates leaf metabolism.
Mowing grass lawn facilitates better maintenance because 
Apical dominance is a common observation in vascular plants. If apical meristem is intact & growing, the lateral tips growth is suppressed. According to Thimann & Skoog the Auxin, synthesized in apical meristem, in translocated downwards & inhibits the growth of lateral tips. That is why mowing grass lawns facilitates better maintenance.
Which one increases in the absence of light?
In general intense light retards growth in plants. High light intensities induce dwarfening of the plant. Absence of light reduces the overall growth, photosynthesis, uptake of minerals and ascent of sap. However, the elongation of internodes is seen to occur in the absence of light.
Leaves of many grasses are capable of folding and unfolding because they 
Monocot leaves have some specialized cells in the epidermal cells of their leaves called bulliform cells (motor cells) which lose or gain turgidity due to which their leaves show coiling and uncoiling.
Hormone primarily connected with cell division is [1988, 1991]
The most important function of cytokinins (zeatin is one of the cytokinins present in Zea mays - the corn) is the promotion of cell division. These are now established as true cell division factors.
Cut or excised leaves remain green for long if induced to root or dipped in 
Because cytokinins help cells in retaining chlorophyll for longer time. Cytokinin delay the senescence (ageing) of leaves and other organs.
Gibberellins promote [1988, 97]
Some light sensitive seeds like Lectuca sativa (Lettuce) germinate in complete darkness with the help of Gibberellins which otherwise require specific light conditions.
Phytochrome is involved in 
Borthwick & Hendricks (1952) gave the concept of phytochrome. Phytochrome is a coloured protein pigment located in plasma membrane to perceive the photoperiodic stimulus in leaves. It may exist in two interconvertable forms Pr and Pfr (red and far red light absorbing forms)
Movement of leaves of Sensitive Plant, Mimosa pudica are due to [1988, 99]
Mimosa pudica (touch me not) leaves show seismonastic movement in response to physical contact. The movement is due to turgor changes due to ejection of water by cells of pulvinus (swollen leaf base) on touching it. It causes folding and drooping of leaves.