叶籽银杏拟胚珠的形态发育及变异特性

以山东省沂源县中国首次发现的叶籽银杏为试材, 对其变异特性、“叶生拟胚珠”的形态发育过程、叶脉以及叶和胚珠的形态进行了研究。结果发现, 叶生拟胚珠的发育过程可分为发端期、形成期、增大期和成熟期。每个叶上叶生拟胚珠1～8个, 但只有一个能正常发育。叶籽银杏的叶片可以分为多裂型、全缘型、二裂型、叶生拟胚珠叶和变形叶, 叶色分绿色和斑叶两种类型; 与正常胚珠相比, 首次发现叶生拟胚珠的数量和着生部位差异较大, 发生时间具滞后性和异时性。叶生拟胚珠的形成期比正常胚珠滞后15 d, 而且在授粉期的叶生拟胚珠上始终未发现“传粉滴”的出现; 叶生拟胚珠按其着生位置分为单裂单生型、单裂簇生型、双裂簇生型、多裂单生型和散生型5种; 叶籽银杏正常叶叶脉具有闭合型、W型、V +W型和双V +W型的网结联合, 而叶生拟胚珠叶的叶脉有单弧形、双弧形和多弧形3种类型。对叶籽银杏这一特异观赏种质的变异特性及系统发育进行了讨论。

Morphological Development of Ovule-like Organ on the Leaf and Variation Characteristics of Ginkgo biloba var. epiphylla Mak.(Ohatsuki)

Many features of Ginkgo biloba var. epiphylla Mak., the one which was firstly found at Yiyuan County of Shandong Province in China, were continually observed and the comparative morphology research was conducted, including the variation characteristics, the morphological development of ovule-like organ on the leaf blade and veins of leaf. The results of analysis showed that the development of the ovule-like organ on the leaf blade is comprised of initial stage, formation stage, expansion stage and mature stage. There were one to eight ovule-like organs on each leaf, but only one developed normally. The leaves were divided into five types, i.e. multilobed type, nonlobed type, bilobed type, the leaf with ovule-like organ and deformation leaf, leaf color into two types, i.e. green and variegated types. Compared with normal ovules, ovule-like organ on the leaf blade displayed variation in insertion, heterochrony and hysteresis in development of ovule-like organ on the leaf blade, which was reported for the first time. The ovule-like organ lagged behind the normal ovule for fifteen days at initial stage, moreover no pollination drop was found on the ovule-like organ. The ovule-like organ on the leaf blade was divided into five types according to the insertion on the leaf, i.e. unilobed solitary type, unilobed clustered type, bilobed clustered type, multilobed solitary type and adsperse type. The vein of normal leaf could be separated into four types according to anastomoses, i.e. closed type, W type, V W type and double V W type. And that of the phyllosporous leaf was classified into three types, i.e. uni-arcuate, biarcuate and mutli-arcuate type. The variation characteristics and the phylogeny of Ginkgo biloba var. epiphylla Mak. were discussed in the paper.