Distribution of plasma membrane rosettes and kinetics of cellulose formation in xylem development of higher plants
Distribution of plasma membrane rosettes and kinetics of cellulose formation in xylem development of higher plants
复制标题
高等植物木质部发育中质膜玫瑰花结的分布和纤维素形成动力学
作者：
B. Schneider;Werner Herth
为了证实和扩展质膜颗粒复合物的频率和分布与纤维素形成有关的信息，在没有冷冻保护的情况下，对几种高等植物——玉米（Zea mays）、绿豆（Vigna radiata）和芥蓝（Lepidium sativum）——的胚根进行了冷冻断裂。在这3个对象中，木质部发育分子的果粉在壁增厚区域均表现出莲座积累。莲座分布模式从幼嫩期的随机分布，到可能的中间阶段的更成组的分布，到后期的严格局部分布。玫瑰花结的频率随阶段而增加。在这三个对象中，木质部元素发育的EF在颗粒中相对较差。对“末端球状体”的观测是罕见且不明显的。这就导致了一种假设，即PF上的玫瑰花结和EF上的末端球不是同一复合体的一部分。将木质部壁增厚下微管的数量和分布与玫瑰花结的频率和分布进行比较，得出这两种结构之间似乎没有直接联系的结论。微管可能参与莲座的分组，从而间接定向微纤维沉积。根据观察到的莲座频率和形成的壁材量计算表明，在木质部发育过程中，每个莲座每分钟可形成1,000 nm的初等原纤维，一个莲座的活性期约为10分钟。
SummaryGerm roots of several higher plants—maize (Zea mays), mung bean (Vigna radiata) and cress (Lepidium sativum)—were freeze-fractured without cryoprotection in order to confirm and extend the informations on frequency and distribution of plasma membrane particle complexes with respect to cellulose formation. In all three objects the PF of developing xylem elements showed rosette accumulations in the regions of wall thickenings. The rosette-distribution pattern ranges from random in a young stage, to more grouped in a probable intermediate stage to strictly localized in later stages. The frequency of rosettes increases from stage to stage.In all three objects the EF of developing xylem elements is relatively poor in particles. Observations of “terminal globules” were rare and undistinct. This leads to the assumption that rosettes on the PF and terminal globules on the EF are not part of the same complex.A comparison of the number and distribution of microtubules underlying the xylem wall thickenings with rosette frequency and distribution leads to the conclusion that there seem to be no direct connections between these two structures. Microtubules may be involved in grouping of rosettes, thus indirectly orienting microfibril deposition. Calculations based on the observed rosette frequencies and the amount of wall material formed indicate that in xylem development 1,000 nm elementary fibril per rosette per minute may be formed and that the active phase of one rosette may be about 10 minutes.