Question

Given what we have discussed about biochemical reactions of photosynthesis in terrestrial plants, what do you suppose are the potential mechanisms plants could use to compensate for a reduction in the biochemical processes of photosynthesis during stress? You should discuss possible stressors and present your answer in two parts. A) Short term responses (acclimation), B) Long term responses (evolution/adaptatation)

list examples of stresses that can lead to a reduction and specifically identify how these stressors will decrease biochemical efficiency (i.e., excess energy)- Demonstrated clear understanding of the short-term and longterm mechanisms for dealing with stress. - Short-term: list 3-5 specific examples Longterm: list 3-5 specific examples

Answer 1

The present study investigates the effect of both long and short term salinity stress in chickpea plants and the protective effect of exogenously applied nitric oxide.

Sodium nitroprusside used as nitric oxide donor.

Salinity treatments given before sowing were termed as long term stress and thirty days after germination as short term stress.

Sodium nitroprusside was given as foliar spray 30 days after germination to both long and short term salinity treated plants.

Increased in membrane injury %, ROS content and lipid peroxidation levels were observed under salinity stress.

Sodium nitroprusside treatments decreased ion leakage and lipid peroxidation levels significantly.

Salinity stress resulted in induction of antioxidatve enzymes but induction was more under short term salinity stress as compared to long term salinity stress.

Nitric oxide showed its positive effect by further increasing the activities of antioxidant enzymes.

Salinity stress also altered the level of antioxidant metabolites by reducing the ascorbate redox ratio and glutathione redox ratio.

No donor treatments increased the redox ratios and showed its positive effects.

Seed yield also decreased under salinity stress with more reduction under long term salinity than short term salinity.

Nitric oxide had a positive effect on seed yield and biomass accumulation.

On the basis of above studies, it is proposed that short term salinity stress resulted in a greater increase in membrane injury (%), malondialdehyde, reactive oxygen species and hydrogen peroxide content as compared to long term salinity stress.

It activated the antioxidant defense system more pronouncedly, resulting in a lesser oxidative stress and a smaller decline in plant yield.

However, long term salinity stress had a lesser effect on antioxidant defense system, thus leading to a higher oxidative stress and ultimately a higher decline in plant yield.