| Summary: | 碩士 === 國立臺灣大學 === 植物學系 === 85 === The early floral development, anther tissue differentiation
and the changes in ultrastructures of microsporocytes, tapetum
and anther wall layer during the development of Lonicera
japonica Thunb. pollen were studied with light and electron
microscope. The ontogenic sequence of flower development was
initiated by sepal and petal primodia, followed by stamen
primodia, and consequently, the pistil primodium.
Immediately after initiation of stamen primodium, it
differentiated toform a four-microsporangiate anther. The anther
wall layers were developedthrough dicotyledonous type and were
composed of of epidermis, endothecium,middle layer (one layer),
and tapetum.The tapetum was dual origin. On pre-meiotic
stage, callose wall was deposited around pollen mothercells with
some cytoplasmic channels between pollen mother cells. The
cytoplasmic channels retained until pollen mother cells have
completed its meiosis. The cytokinesis of pollen mother
cells in Lonicera japonica Thunb. was simultaneous. Once meiosis
was started, the tetrahedral tetrads enclosed in the callose
wall was formed. After callose wall was dissolved, four
microspores were released into the anther loculus, where mitosis
was taking place, producing a big vegetative cell and a small
generative cell. The generative cell wall was then
dissloved, and many oil drops accumulated around generative cell
which sliped into the center of vegetative cell later.Before
pollen grains maturation, a number of starch grains were
appeared in them. The mature pollen grains were tri-colporate;
oil drops and starch grains were the main storage materials.
Tapetal cell wall began to degenerate on pre-meiotic stage, but
tapetal cells invaded around microspore after free microspore
stage. On bicellular stage, the border of tapetal cells was not
evident and then the tapetal materials penetrated into cavity of
bacula of pollen wall. At amyloplast stage,tapetal cell
inclusions reduced as residuces rapidly while lots of starch
grains accumulated in pollen grain. At anthesis, the residuous
tapetum as a film containing polysaccharides and lipid coated
around the mature pollen grain. At the tetrad stage,
fibrous glycocalyx was deposited between the callose wall and
cell membrane of tetraspores. Primexine was accumulated on
glycocalyx,on which exine material secreted by microspore was
also accumulated. The accumulation of exine including spines,
tectum, bacula and foot layer has beenpartially finished before
callose was dissolved on amyloplast stage. While the formation
of intine was first initiated at bicellular stage and finished
at amyloplast stage as exine. The results of this study
present a detailed in formation about the microsporogenesis and
pollen wall development of Lonicera japonica Thunb.,
andascertained that exine is derived from a combined
contribution from tapetum and microspore, rather than from
either of them.
|
|---|
