In plant physiology, the 'Photoperiodism' refers to the response of plants to:
A. The relative lengths of day and night (light and dark periods)
B. The intensity of light
C. The direction of light
D. The wavelength of light
Answer: Option A
Solution (By JKSSB Mock Tests)
Photoperiodism is the physiological reaction of organisms, particularly plants, to the length of the day or a dark period. It is the mechanism by which plants measure the relative lengths of light and dark periods to regulate developmental processes, most notably the timing of flowering. Plants are classified as short-day plants, long-day plants, or day-neutral plants based on their flowering response to photoperiod. The photoreceptor pigment phytochrome is crucial in perceiving these light/dark signals.
Explanation:
The Philadelphia chromosome is a specific genetic abnormality found in the bone marrow cells of most patients with Chronic Myelogenous Leukemia (CML). It is formed by a reciprocal translocation between the long arms of chromosome 9 and chromosome 22, denoted as t(9;22). This translocation fuses the BCR gene on chromosome 22 with the ABL1 gene on chromosome 9, creating a mutant BCR-ABL1 fusion protein with constitutive tyrosine kinase activity, driving uncontrolled cell division.
Explanation:
Albert Sabin developed the attenuated oral polio vaccine (OPV), which is easier to administer and provides intestinal immunity. Salk developed the inactivated vaccine (IPV).
Explanation:
Adventitious roots arise from non-root tissues like stems, leaves, or branches. Examples: prop roots of banyan, stilt roots of maize, aerial roots of orchids. Taproot and fibrous roots develop from the radicle.
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