水稻種子發育成熟時，必需歷經脫水乾燥的過程，此過程可視
為一種脫水乾燥逆境。稻穀成熟後乾燥貯藏，貯藏期間對稻穀
而言是一種老化過程。脫水乾燥及老化過程皆可能發生氧化傷
害，使生物體處於氧化逆境。Glutathione是生物所含的主要硫
醇化合物，一般硫醇化合物具有抗氧化逆境的功能，保護生物體
免受氧化傷害，維持生命力。為了解硫醇化合物在種子發育及老
化過程所扮演的功用，本試驗以水稻為材料，調查稻穀發育及貯
藏期間，硫醇化合物含量及型態的變化。
試驗結果顯示，在穀粒發育期間，隨著穀粒發育日數，水稻種子
的鮮重、乾重呈典型的生長曲線增加，相對地種子內水份含量下
降。成熟期水份含量低於30 %，伴隨著穀粒發育日數增加，胚及
穎果內glutathione總含量及GSSG含量增加，唯GSH則隨發育期逐
漸減少。另外，PSSG、硫醇化合物總量、游離態硫醇化合物及二
硫化物等含量在穀粒發育期間大致維持一定水平，開花10天後至
成熟期，其含量變化不顯著。稻穀的胚含有較高濃度的各類硫醇
化合物。稻穀成熟時，胚及穎果中所含的glutathione主要為氧化
態，此時GSSG佔glutathione總含量的78 ∼80 %，此現象顯示成
熟時乾燥的種子處於氧化逆境中。
稻穀貯藏期間，胚及穎果內glutathione總含量、GSH、PSSG等含
量皆隨著貯藏期延長而呈線性減少。由於部份glutathione在貯
藏期間氧化，故貯藏前六個月，GSSG有增加趨勢，但隨後亦減
少。10℃低溫貯藏可減緩glutathione的氧化速率。雖然glutathione
的氧化還原狀態和種子發芽能力無直接關連，但glutathione的改變
速率可能可作為水稻種子貯藏品質的一種指標。

Changes in thiol status of rice (Oryza sativa L.)
seed during development and storage

Summary

Seed development and storage could be thought as a dehydrate
condition and aging process , respectively. Dehydration and
aging are frequently thought to involve oxidative damage that
could be prevented or counteracted by antioxidant substrates.
It is well known that non-protein sulfhydryl compounds (thiol)
are essential in cellular functioning but also sensitive to
oxidative stress in general. In order to elucidate what role do
such thiol compounds changes play in seed development and storage.
We therefore investigate the thiol content and it*s redox state
in different seed development and storage stages.
In rice seeds, total glutathione and oxidized glutathione showed
a marked increase but reduced glutathione decrease in caryopsis
and embryo during seed development. Bound form glutathione, total
thiol content, free thiol content and disulfide maintain in same
levels during seed development. Analysis of glutathione redox in
seed at various stages on development indicated that high
percentage( 70-80 %) of glutathione is in oxidized form.
Matured rice seeds contained the highest concentrations of
glutathione and largely maintained in its oxidized form,
which is an indication of oxidative stress. Embryo is a major
sink for the accumulation thiol compounds during seed development.
Analyses of germination, thiol compounds in seed under different
storage conditions indicated that total glutathione, reduced
glutathione, bound form glutathione and total thiol content in
caryopsis and embryo were decreased linearly at ambient condition.
Levels of oxidized glutathione increased before six months storage
but decreased later. These results also reflected oxidative stress
under storage condition. Seeds stored at 10℃condition could relief
the degree of glutathione oxidation. Although data showed that the
viability of rice seed was not directly related to the redox status
of thiol compounds, but changes of glutathione status might be a good
indicator of seed quality during storage.