Development of male gametophyte of Larix leptolepis Gord. with emphasis on diffuse stage of meiosis.
A basic developmental framework of the Larix leptolepis Gord male gametophyte is presented in detail by squashing technique. The duration of the meiosis stage was more than 6 months, and included a long diffuse stage during winter. This long duration of the diffuse appearance of the diplotene stage makes L. leptolepis a unique suitable experimental material for studying the structure and function of the diffuse stage of meiosis. In particular, the processes of desynapsing and unpairing, which so far have received little attention, can be examined in detail. In L. leptolepis, the chromosomes undergo a dramatic structural reorganization during the diffuse diplotene stage. Based on the clearly visible differences in chromosome morphology, the diffuse diplotene stage was divided into four periods with suggested nomenclature as follows: schizonema, pre-diffuse diplotene, diffuse diplotene and post-diffuse diplotene. Both simultaneous and successive microsporogenesis were observed within L. leptolepis, and there was no strict relationship between the microsporogenesis types and the tetrad configurations, which are strongly influenced by spindle orientation, especially during meiosis II. The mature pollen grain at pollination consists of five cells aligned in an axial row. The prothallial cells cannot be regarded as senescent cells because they remain capable of division.
Zhang
Shou-Gong
SG
Laboratory of Cell Biology, The Research Institute of Forestry, Chinese Academy of Forestry, Beijing, People's Republic of China.
Yang
Wen-Hua
WH
Qi
Yu-Chen
YC
Li
Mao-Xue
MX
Wang
Jian-Hua
JH
Sun
Xiao-Mei
XM
Wang
Xiao-Shan
XS
Qi
Li-Wang
LW