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北美地理学paper代写:授粉阶段

在授粉阶段对玉米的影响是另一个关键阶段,它将影响玉米的繁殖和每穗形成的粒数。“在吐丝前7到10天的干旱胁迫会导致蚕丝发育延迟(爱荷华州立大学,2017)。Hunker将吐丝定义为“流苏或玉米丝从玉米穗中出现的阶段”。这通常发生在玉米幼苗从地里长出来55-66天后。在这个阶段,玉米已经准备好授粉(Tun, 2011)。干旱甚至会导致开花吐丝间隔差(ASI)。这一阶段的压力增加了授粉所需的时间,也增加了花粉在吐丝前脱落的机会(普渡大学)。水分胁迫不仅会延迟吐丝,还会降低蚕丝伸长,严重时还会阻碍胚胎发育(爱荷华州立大学,2017)。这一阶段的需水量处于峰值,任何高温或干旱胁迫都会影响最终的粮食产量(Ciampitti等,2017)。Claassen和Shaw发现,“在吐丝之前、吐丝期间和授粉之后,由于干旱相关的压力而导致的产量下降与籽粒数量的显著减少有关(Claassen和Shaw, 1970)。“养分胁迫也可以在干旱胁迫期间表现出来,这是由于土壤的最上层变得干燥,无法到达活性根系提取区(普渡大学)。我们可以得出结论,在授粉、抽雄和吐丝期间的干旱胁迫对潜在的最终产量非常不利。

北美地理学paper代写:授粉阶段

Effects on corn during the pollination stage is another critical stage that will influence how the corn reproduces and the number of kernels that form per ear. “Drought stress seven to ten days ahead of silking can result in delayed silk development (Iowa State University, 2017).” Hunker defines silking as “the stage when the tassels or corn silk emerges from the ear of the corn. This usually occurs around 55-66 days after the corn seedling emerges from the ground. At this stage, the corn plant is ready to be pollinated (Tun, 2011).” Drought can even result in poor anthesis silking interval (ASI). Stress during this stage increases the time required for pollination, as well as the chance that pollen being shed before the silks emerge (Purdue University). Water stress will not only delay silking, but also reduce silk elongation and if severe, impedes embryo development (Iowa State University, 2017). Water demands during this stage are at their peak and any heat or drought stress will effect final grain yield (Ciampitti et al., 2017). Claassen and Shaw discovered that “Significant reductions in kernel numbers were associated with yield reductions from drought-related stress before or during silking and after pollination (Claassen and Shaw, 1970).” Nutrient stress can also be exhibited during this time of drought-stress due to the uppermost part of the soil becoming dry and out of reach of active root extraction zone (Purdue University). We can conclude that drought-related stress during the pollination, tasseling, and silking stage can be very detrimental to the potential final yield.