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草莓适应强,省肥,易管理,是一种效益好的经济作物,在一封闭的草莓大棚中, 某生物兴趣小组测量了 48 小时内棚内二氧化碳含量,绘制了如下示意图(图 12 ) , 据图回答问题: ( 1 )你认为 曲线 ab 段下降的原因是 。草莓吸收的水分主要是用于 。 ( 2 )为了提高草莓产量, 生物兴趣小组同学们建议果农:晚上适当增加光源;开花期间,在棚内放养一群蜜蜂。你建议果农在 bc 段还可以采取的 措施是 。 ( 3 )为了增加草莓的甜味,合理施用含 的无机盐可以达到目的。 ( 4 )有的一株草莓上开了很多花或结了很多果,有经验的 果农并未全部保留,而是进行、,只保留少数。这样做的目的是为了使保留的果实有充足的 供应, 提高草莓的品质。
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