旱生植物驼绒藜茎的异常次生结构及其发育

ANOMALOUS SECONDARY STRUCTURE AND GROWTH IN THE STEM OF XEROPHYTE, GERATOIDES LATENS

藜科旱生植物驼绒藜(Ceratoides latens)成长茎由木栓组织、异常形成层、不规则排列的异常维管束及其间的木质化厚壁结合组织和中央正常的维管柱所组成。木栓组织很发达。异常形成层连成环状。异常维管束外韧型。结合组织细胞紧密围绕在各个异常维管束之间。正常的次生维管柱由数个扇形维管束组成,位于维管束内的束中形成层已失去分生能力。中央的髓细胞大多破毁。在茎的发育过程中,初生生长和早期的次生生长都是正常的。而以后的次生生长由初生韧皮部外方保留的原形成层细胞发生的异常形成层活动所代替。起初,异常形成层仅向内交替产生结合组织细胞和异常维管束,而后来同时还向外分化木栓细胞。这种异常的次生结构对旱生植物具有重要的生态学意义。

The anomalous secondary structure and growth in the stem of xerophyte, Ceratoides latens, was studied. A developed stem consists of phellem which is well developed, Anomalous strands was arranged at random and embedded by lignified as well as sclerified conjuctive tissues and a normal vascular cylinder. In the course of stem development, primary and secondary growth in the early stage is similar to that of ordinary dicotyledons. The secondary thickening is then replaced by the activities of anomalous cambium arising from the procambial cells remaining between cortex and primary phloem. Initially the cambium gives rise to fasicular strands and conjuctive tissues alternately only on its inner side, and then differentiates bidirectionally, i. e. , fasicular strands and conjuctive tissues centripetally and phellem centrifugally. The anomalous secondary structure has an important ecological significance for xerophytes.