试论竹类的花序及其演变

本文旨在讨论竹类花序的类型。它共有两大类型,即单次发生花序(简称“真花序”)与续次发生花序(简称“假花序”)。前者具有一延续的花序轴,这与竹类的一般营养轴是迥然不同的;此外,整个花序是在一单次发育的周期内所产生的,并且它在植物体上有着一定的生长部位;它们的基本单位是小穗(真小穗),每小穗通常具一明显的柄。后一类型,则实是竹株的具花枝条,而非是真正的花序,故称为“假花序”。它具有原来就是营养轴所成的“花序轴”,此轴仍有节与节间两部分的区别,仅在其节处始能生有小穗;它们在发生上是续次(successivus)的,其小穗可不固定地着生在植物体任何级别的营养轴之各节,甚至可直接生长在主竿的节上;生长在此种类型花序上的通常或大多是假小穗,它无柄或近于无柄。多数情况都是形成紧密的簇团。又此种类型的花序仅见于竹类的一部分属种中,而决不发现在其他禾草(包括另一部分的竹类)的植株上。作者认为真正的花序可以通过演化而转变为续次发生的花序即“假花序”。举例来说,他曾设想筱竹Thamnocalamus spathiflorus Munro含2-3枚小穗的总状花序能够演化为浦竹仔Indosasa hispida McClure那样形态的一小段花枝。作者还相信在竹类的两大类型的花序之间并非仅有一个方向的演化途径,甚至还可能有着逆向演化之存在。

A PRELIMINARY STUDY OF THE INFLORESCENCE TYPE ARISING FROM BAMBOOS AND ITS VARIATION

There are two types of the bamboo inflorescences which have been proposed in the present paper. One is the true inflorescence, and the other is referred by some authors to false one. The true type of bamboo inflorescence has a continuous main axis, develops in a semslauctant period of histogenesis, and grows from a determinate portion (or special portions) of the bamboo-body. The fundamental units of this type are genuine spikelets usually each with a distinct pedicel. The so-called false type, however, is surely a blooming leafy branch and not the inflorescence proper. It has a jointed axis (originally a vegetative branch) with spikelets attached to the nodes. It develops in iterauctant periods of histogenesis, and the spikelets (or pseudospikelets) grow indeterminately on the nodes of any branching axis or even of main culm. The fundamental units found in the so-called false type of bamboo inflorescence usually are pseudospikelets. They are generally sessile or nearly so and mostly in compact clusters or fascicles.It is the writer's opinion that mostly the so-called false type may have evolved from the true one. For example, the inflorescence of Thamnocalamus spathiflorus Munro is racemose with 2-3 spikelets, which is very similar to the flowering branchlet of a more primitive bamboo species with "false" inflorescence Indosasa hispida McClure. Of course, between the true type and the so-called false one a reverse direction of evolutionary line can also be found.