Abstract Grain growth and leaf senescence are the main processes during post-silking in maize. An unanswered question is how changes in sink strength (the number of grains to be filled) affect leaf senescence. We studied the effect of changes in the source-sink ratio during grain filling on the dynamics of green leaf area and photosynthetic rate. Maize plants were exposed to ear removal, pollination prevention, degraining or defoliation treatments during post-silking in two sowing dates. Green leaf area, leaf photosynthetic rate and leaf greenness were periodically measured. At maturity, yield, grain weight, and stem dry weight were determined. Green leaf area loss showed a first phase of slow senescence followed by a second phase of rapid senescence in all conditions. The response of green leaf area duration (GLAD) to the source-sink treatments depended on environmental conditions: ear removal increased GLAD while defoliations reduced it in the early sowing date, though GLAD was unaffected by these treatments in the late sowing date. But any change in senescence was less than proportional to the changes in the source-sink ratio. Leaf photosynthetic rate or leaf greenness (SPAD) did not change with the source-sink treatments. Defoliation caused a remarkable remobilisation of reserves from the stem, which did not fully mitigate the reduction in grain weight. It is concluded that (i) manipulations of source-sink balances modified slightly leaf longevity but not the functionality of the remaining leaf area (leaf photosynthetic rate), the response of GLAD being dependant on environmental conditions, and (ii) grain weight was more susceptible than GLAD to reductions in source-sink ratio.

中文翻译：

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不同源库比下的玉米衰老在谷物灌浆期

摘要 籽粒生长和叶片衰老是玉米后丝绸过程中的主要过程。一个悬而未决的问题是汇强度（要填充的谷物数量）的变化如何影响叶片衰老。我们研究了灌浆过程中源库比变化对绿叶面积和光合速率动态的影响。玉米植株在两个播种日期的后丝绸过程中进行除穗、防止授粉、脱粒或落叶处理。定期测量绿叶面积、叶光合速率和叶绿度。成熟时，测定产量、粒重和茎干重。在所有条件下，绿叶面积损失显示出第一阶段的缓慢衰老，然后是第二阶段的快速衰老。绿叶面积持续时间 (GLAD) 对源库处理的响应取决于环境条件：摘穗增加了 GLAD，而在播种早期落叶减少了 GLAD，尽管 GLAD 在播种后期不受这些处理的影响。但是衰老的任何变化都与源汇比的变化不成正比。叶光合速率或叶绿度 (SPAD) 不随源库处理而改变。落叶导致茎干储备的显着再动员，这并没有完全减轻粒重的减少。得出的结论是（i）对源库平衡的操纵略微改变了叶片寿命，但没有改变剩余叶面积（叶片光合速率）的功能，GLAD 的响应取决于环境条件，