<div><br></div><div><section class="_135editor" data-role="paragraph" style="font-size: medium; max-inline-size: 100%; margin: 0px; padding: 0px; border: 0px none; z-index: 0; overflow-wrap: break-word !important; outline: none 0px !important;"><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 15px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉花大多是一年生植物。它的一生按生育周期分,要经历种子发芽、出苗、主基和枝叶的生长、现蕾、开花、结铃、吐絮几个时期。这些时期按其生长发育规律可分为五个不同而连续的生育阶段。第一阶段为播种到出苗;第二阶段为出苗到现蕾;第三阶段为现蕾到开花;第四阶段为开花到吐絮;第五阶段为吐絮成熟。棉花各生育期所需时间随品种、特性、环境条件及栽培方法的不同而长短不一。一般来讲,我国在四五月开始播种,一两星期后开始发芽,随后生长发育变快,最后形成棉株。棉株上的花蕾在七八月间陆续开花,开花期可延续一个月以上。花朵受精后就萎谢,花瓣脱落,开始结铃。棉铃由小到大,45～65天后成熟。这时棉铃外壳变硬,裂开后棉絮外露,称为吐絮。吐絮后就可收摘子棉。根据收摘时期的早晚,有早期棉、中期棉和晚期棉之分。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 15px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉株生长到一定阶段,果枝上就长出花蕾。花蕾内部有一个子房,将来长成棉铃。子房内部有许多胚珠,将来长成种子。每个胚珠的表皮有很多长条形的细胞,其上发生突起,这种突起的细胞以后成为棉纤维的初生胞壁。每根棉纤维是一个植物单细胞(有一个细胞核),经过突起、延伸和发展而成。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 15px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉纤维与棉铃、种子同时生长。在花冠张开之后,胚珠受精之前,它的表皮细胞就发生突起。但胚珠一定要受精,才能长成种子,其突起的细胞,一部分长成棉纤维,另一部分成为绒毛,即棉短绒(对种子起保护作用)。有些棉花的种子没有绒毛,即光子,这可能与品种特性有关。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 15px; overflow-wrap: break-word !important; outline: none 0px !important;">　　未受精的胚珠,只能成为不孕子,其突起的细胞可以长到10～20mm,成为不孕子纤维。一般陆地棉每粒种子上生长的棉纤维数量为10000～15000根,每个棉铃内生长的种子和不孕子为20～40粒,不孕子的粒数常占种子数的10%～30%。检验证明,种子&nbsp; &nbsp;上棉纤维根数的多少,主要决定于品种的优良程度。退化种棉纤维根数较少。种子和不孕子的总数随品种而不同,一般陆地棉每瓣子棉中常有7～9粒种子。不孕子的多少,决定于胚珠受精率的高低,它多在棉瓤的基部。因此,良种的选育和保纯、胚珠的受精,尤其是使子房底部的胚珠多受精对棉花增产有重要意义。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; line-height: 1.75em; overflow-wrap: break-word !important; outline: none 0px !important;"><span style="max-inline-size: 100%; margin: 0px; padding: 0px; cursor: text; font-size: 15px; overflow-wrap: break-word !important; outline: none 0px !important;">　　棉纤维的生长发育很特别,首先只长长度,然后充实胞壁,最后干涸成形。从胚珠表皮细胞开始突起到棉铃开裂干涸成形,分三个时期。各期生长变化及品质差异与环境条件关系极大,对生产管理、收获方法和采摘时间都有一定的要求。</span></p><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; overflow-wrap: break-word !important; outline: none 0px !important;"></p></section><section class="_135editor" data-role="paragraph" id="autoparagraph" style="font-size: medium; max-inline-size: 100%; margin: 0px; padding: 0px; border: 0px none; z-index: 0; overflow-wrap: break-word !important; outline: none 0px !important;"><p style="max-inline-size: 100%; margin-bottom: 0px; clear: both; min-height: 1em; cursor: text; overflow-wrap: break-word !important; outline: none 0px !important;"><br style="max-inline-size: 100%; margin: 0px; padding: 0px; font-family: 微软雅黑, &quot;Microsoft YaHei&quot;, sans-serif; font-size: 17px; 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