| 其他摘要 | Drought stress affects the growth and yield of crops seriously. So how to delay leaf
senescence and increase the drought resistance of crops are significant. Carbon and
nitrogen metabolism is the material basis of crop growth and yield, it plays an important
role in regulation of leaf senescence. And nitrogen has a certain impact on crop drought
resistance as an essential element for plant growth. Therefore, to investigate the influence
of nitrogen on carbon/nitrogen balance and leaf senescence under drought stress, and the
association with drought resistance. In this study, we select different maize varieties as the
research object, set different nitrogen levels, as well as drought stress and rehydration.
Which to investigate the influence of nitrogen on carbon/nitrogen balance of leaf
senescence under drought stress and rehydration. The main conclusions are as follows:
1. Drought stress induced the maize leaf senescence. The net photosynthetic, Fv/Fm
and chlorophyll content decreased significantly under drought stress in different maize
varieties. And the different varieties affected by the drought stress are different, there is a
difference between maize varieties.
2. Drought stress induced the imbalance of carbon and nitrogen. Under drought stress,
the maize leaf accompanied with the accumulation of soluble sugar content, slightly
changed of starch content, decreased of total nitrogen content, and increased of
carbon/nitrogen ratio, carbon and nitrogen balance was damaged. Both the non-structural
carbohydrates content and carbon/nitrogen ratio showed a significant negative correlation
with chlorophyll content, and there was a significant positive correlation between total nitrogen content and chlorophyll content. Therefore, the carbon/nitrogen balance may
involve in the regulation of drought-induced leaf senescence.
3. Under normal water conditions, it increased the net photosynthetic, Fv/Fm and
chlorophyll content of maize leaf when increased the content of nitrogen. Which enhanced
the internal physiological metabolic activity in maize leaf. Drought stress severely
inhibited the net photosynthesis rate of maize leaf, Fv/Fm and chlorophyll content dropped
significantly. But these indicators in maize leaves are affected severely under high nitrogen
levels. By shoot dry weight calculations and we found that drought resistance and recovery
capacity under high nitrogen level are significantly lower than low nitrogen level. Which
indicated that nitrogen increases the drought stress sensitivity of maize under drought
stress.
4. After drought and rehydration, the biomass, leaf relative water content,
photosynthetic parameters and other indicators of maize were recovered. However, carbon
and nitrogen imbalance which induced by drought stress was not quickly recover. Soluble
sugar content and carbon/nitrogen ratio continued to rise, and total nitrogen content
continued to reduce. This indicated that leaf senescence sometimes may accelerated after
drought and rehydration. The senescence may related to carbon/nitrogen ratio could not
back to normal soon.
From the above results, we can obtain that leaf senescence and carbon/nitrogen
imbalance of drought stress and recovery are highly correlated. Which indicated that
carbion/nitrogen imbalance may be involved in the regulation of leaf senescence.
Key words: maize; drought; leaf senescence; nitrogen; carbon/nitrogen balance |
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