Avena curvature test is a bioassay for examining the activity of
auxins
cytokinins
gibberellins
ethylene.
A.
auxins
Bioassay is a testing of biological activity like growth response of a substance by employing plant part. Avena curvature test is a bioassay for examining the activity of auxins. It is based upon experiments of Went. 10° curvature is produced by auxin concentration of150 g/lit at 250C and 90% relative humidity. It can measure auxin upto 300g/litre. Auxin from shoot tip or any other plant organ is allowed to diffuse in a standard size agar block. 15- 30 mm long oat coleoptile grown in dark is held vertically over water. 1 mm tip of colcoptile is removed without injuring the primary leaf. After 3 hours a second decapitation is carried out for 4mm distance. Primary leaf is now pulled loose and agar block supported against it at the tip of decapitated coleoptile. After 90- 100 mm the coleoptile is found to have bent. The curvature is measured
In a plant organ which is covered by periderm and in which the stomata are absent, some gaseous exchange still takes place through
aerenchyma
trichornes
pneumatophores
lenticels.
The plants respond to photoperiods due to the presence of :
enzymes
stomata
phytochromes
phytohormones
Cork cambium results in the formation of cork which becomes impermeable to water due to the accumulation of
resins
lignins
suberin
tannins.
Pruning of plants promotes branching because the axillary buds get sensitized to
ethylene
gibberellin
cytokinin
indole acetic acid.
Gibberellins can promote seed germination because of their influence on
rate of cell division
production of hydrolyzing enzymes
synthesis of abscisic acid
absorption of water through hard seed coat
'Climacteric' is
a phenomenon related to fruit ripening
the condition of a plant when all its fruits are almost ripe
the condition of a plant when most of its leaves have turned yellow
none of the above
