| Summary: | 碩士 === 國立臺灣大學 === 植物學系研究所 === 86 === Abstract Artocarpus heteroqhyllus Lam., Machilus
japonica var. kusanoi Hayata, Cyclobalanopsis glauca (Thunb.) Oerst, Litsea a
cuminata (Blume) Kurata and Leucaena leucocephala Lam. are five woody species
distrributed in the low forests of Taiwan. This thesis investigated their seed
morphology and the anatomical characteristics, including the composition of i
nsoluble storage materials, the ultrastructure of plumule and apex of radicle
of the embryo axes. Besides the effects of desiccation on the seed viability a
nd the ultrastructure of embryo axes were studied. The
results showed that Art
ocarpus has the biggest seed mass, however, the size of its embryo axes is sim
ilar to that of Leucaena. Among the five species the seed of Leucaena is the s
mallest one. With the exception of Cyclobalanopsis, all the other embryo axes
in matured seed are full-grown andgenerally with 4-6 primary leaves. In the c
otyledons and embryo axes of the seeds of Machilus, Cyclobalanopsis and Litsea
there are secretory mucilage or oil cells. The seeds of Artocarpus obviously
contain laticifers in the cotyledons and embryo axes. However, tannic cells ar
e ubiquitously distributed in the cortex and epidermis of embryo axes, primary
leaves and root caps of the seeds. The predominant
compositions of insoluble
storage materials in the seeds of these five species are starch grains, protei
n bodies and oil droplets. The starch grains are distributed in the ground tis
sue of embryo axes of Artocarpus , Machilus and Litsea.. The oil droplets are
located in the cytoplasm of the cells of embryo axes and in the marginal areas
of the cells of plumule and radicle apex. Nevertheless, in the seeds of Leuca
ena, the oil droplets are mostly observed around the proteins bodies in the pe
ripheryn of the cells in he embryo axes.The highest and lowest moisture conten
ts of mature seed are fong in Artocarpus (61.03%) and Leucaena (6.7%) respec
tively, and the rates of germination are 60% (Artocarpus ) , 95.04% (Machilus
), 96% (Cyclobalanopsis ), 93.33% (Listea) and 94% (Leucaena）. When the seeds
were lost dehydrated 6% (Artocarpus ), 7.5% (Machilus), 17% (Cyclobalanopsis)
, 35% (Lacumunata) of their moisture contents by the saturated lithium chlorid
e (LiCl), the rate of germination decreased dramatically. Among the five woods
, the seed of Lacumunata are the most resistant to low temperature storage (4
0C) and seed of Artocarpus are more susceptable to low temperature treatment.
These results suggest that the degrees of desiccation susceptibility of these
seeds are Artocarpus, Machilus, Cyclobalanopsis, Litsea and
Leucaena. The ultr
astructural study on the seeds showed the cells of plumule and radicle apex ha
s dense cytoplasm, and a large nucleus occuping 20-30% of the cell volumn. The
size of vacuoles in the cytoplasm widely varies with the species. In the cyto
plasm of Leucaena, the mitochondria, endoplasmic reticulum and plastids are se
ldom observed, however, in other species these organelles are ubiquitous distr
ibuted and metabolic active. During the drought stress,
the seed coat, cotyle
don and embryo axes are obviously shrunk. The ultrastructural change in the ce
lls of plumule apical meristem are fusion or lysis of tonoplast, deformation o
f nucleus and nucleolus, shrinkage of protoplasm, and formation of small vesic
les in the cell periphery. A similar, but less significant change was observe
d in the radicle apex, however, the cells in the radicle showed dramatic plasm
olysis and vacuolation. In summary, the present study
suggested that the more
resistant to the desiccation a seed, the more densely of the cytoplasm in the
cells of apex of plumule and radicle. Besides, in the desiccation resistant se
eds the vacuoles are small or lack, and the predominant storage compounds are
oil droplets and protein bodies. The vacuolation of the apical meristematic ce
lls and the activity and the quantity of organelles in the cells of embryo axe
s are increased with the desiccation susceptibility of the seeds. In the seeds
of the five studied species, , highly vacuolation was only found in the plumu
le and radicle of Artocarpus seed, and the degree of vacuolation in the other
four species is not significantly different, but is highly associated with th
eir desiccation susceptibility. VII
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