Question

)Explain how mutants have and can be useful in understanding which photoreceptors are involved in a response.

Answer 1

Effective monitoring of the ambient light environment is fundamental to plant growth and development. Through the action of specialised photoreceptor, plants monitor the quantity, quality and photoperiod of incident light, u and this information to modulate all aspects from the seed to germination to plants architecture and onset of flowering. Three principal families of photoreceptor have been identified invlved in a response the light perception in higher plants tissues, the red/far-red light absorbing phytochromes and the blue -uv light absorbing cryptochromes and photorophs.

Mutant deficient in combination of phyA, phyB, and phyE have shown ambient temperature to modulate the light regulation of Arabidopsis germination. At this point of mutant deficiency phytochromes family members were shown to display altered functional hierarchies at different temperatures. Light signals also act to restrain hypocotyl extension, while stimulating the opening and expansion of cotyledons, and the synthesis of chlorophyll. The analysis of mutants null for multiple receptors has also revealed roles for individual phytochromes in modulating internode elongation and leaf morphology. Mutants roles on phyB shows in modulating plant architecture have recently been proposed in the regulation of stomatal development. Mutants in phyB reduced stomatal index higher photon irradiances of both W and R. In case of flowering the roles of individuals photoreceptors mediating responses have been largely inferred from mutant analyses. Mutants studied has also revealed roles for phyC in the regulation of Arabidopsis flowering time.