摘要
糜子的营养生长锥为半圆球体的形状。生长锥在过渡到生殖阶段前体积略微增大,在高度方面增加更多,但仍没有超过生长锥的直径。生殖阶段的开始,表现在苞叶突起在生长锥的基部周围出现,及第一级分枝原基在苞叶的叶腋间发生。第一级分枝在主轴上的发生次序是向顶的。就整个花序讲,在主轴的基部,分枝原基从苞叶的叶腋间发生的现象十分清楚,但愈往上,这种现象愈不明显,大约在主轴的中部,苞叶和分枝原基往往同时发生,形成双突起的形状;接近主轴的顶端部分,分枝原基发生时常看不见苞叶的显现。主轴生长锥继续伸长,第一级分枝原基继续从它的周围产生;同时已形成的第一级分枝不断地延长,基部比较膨大,成扁平锥体状。苞叶在这时已消失。第二级分枝原基首先在第一级分枝基部膨大部分的两侧发生,然后向上推移,是向顶的发生次序。这种向顶的发生次序同样表现在第二级分枝在花序主轴上的出现。应该指出,自第二级分枝原基发生时起,以后各级分枝发生时未见有苞叶出现。第三、四、五级分枝依次在第二、三、四级分枝上发生。它们在分枝上的发生次序也是向顶的。但是这些分枝在花序上的出现次序发生改变,它们首先在主轴中间偏下部分的分枝上发生,然后向两端的分枝推移。第三、四级分枝的排列和第二级一样,为左右二列;唯第五级分枝仅位于第四级分枝的一侧。当第三级分枝在花序上出现时,花序的主轴顶端开始转向小穗的形成,这种转变逐渐向花序下部的分枝推移。因此小穗在花序上的分化次序与分枝的发生正相反,是向基的。小穗向基的分化次序同样表现在各级分枝上。小穗本身的分化次序是:外颖、内颖、第一花外稃、第一花原基、第二花外稃、第二花原基。小穗生长锥的残余部分保留在第二花原基的旁边,成为小突起的形状。花的分化次序是:内稃、花药和雌蕊、浆片。必须说明,花序各部分的发育时期相差甚远,在一个抽穗(即花序顶部露出于最后一营养叶)的花序上,在同一时间内可以观察到小穗发育的各个时期,从花序基部向上,有开始分化内外颖的小穗,也有雌雄蕊的形态已经建成的小穗。
Developmental investigation of the panicle of the millet was carried out in the Department of Biology, University of Peking in the years 1957 and 1958. This first report deals with the morphology of the development of the panicle. Observations were based on material dissected out under a binocular dissecting microscope. The vegetative shoot apex of the millet is in the form of a hemisphere. 14 or 15 and occasionally 16 leaves are produced when the vegetative apex is changed into the reproductive apex. During the transformation, the apex enlarges, increasing both in height and in diameter. But, unlike conditions obtaining in cereals such as the wheat, in the millet, height of the reproductive apex never exceeds its diameter. The first sign of initiation of the inflorescence is the appearance at the base of the shoot apex of a primordium of the bract which is rudimentary. In the axil of this rudimentary bract arises the axillary branch of the first order. The panicle of the millet is composed of branches of 5 successive orders. The formation of the first order branches is acropetal and in spirals. At the base of the axis, the axillary nature of the first order branches is clearly demonstrable. But the higher branches arise earlier and earlier in relation to the subtending bract. Thus, in the middle part of the axis, the primordium of the bract and that of the branch arise simultaneously, and towards the top the bract is so weakly developed that it is often hardly discernable. Branches of the second order arise laterally, right and left on those of the first order. From now on, the subtending bract no longer appears. Branches of the third, fourth and fifth orders arise respectively on those of the second, third and fourth orders. Spikelets are produced in the basipetal order. The first spikelet is formed at the tip of the main axis; later ones appear in succession at tips of branches of higher and higher order. Two florets are formed in each spikelet, but the first one degenerates. Thus, in each spikelet, only one grain matures. At flower initiation, the lemma appears first and then the primordium of the floret is formed in its axil. This supports the view that the lemma is in the nature of a bract subtending the flower, while the palaea is the first foliar member of the flower. In the development of the spikelets, the constituent parts develop in the following order:the outer glume, the inner glume, the lemma of the first floret, the primordium of the first floret, the lemma of the second floret and finally the primordium of the second floret. The order of the development of members of the flower is:the palaea, the stamens and the pistil and lastly the lodicules. The time-span for the development of different parts of the whole panicle is great. Thus, in an emergent panicle spikelets at various stages of development may be observed. At the top of the panicle the stamens and the pistil may be already differentiated; while at the lower part glume primordia may just begin to appear.
