Uncovering the mechanism of hydrogen sulfide (H2S) in
improving rice seed germination under aluminum (Al) toxicity conditions is
important for rice production in acidic soil. In the present study, an Al
sensitive rice variety Kasalath was used. Pretreatment with 0.1 mmol/L sodium
hydrosulfide (NaHS, H2S donor) under 70 mmol/L AlCl3 (indicated
as Al + NaHS treatment) increased rice seed germination by 27.95%, germination
potential by 474.16%, and the germination index by 43.44%, compared with Al
treatment. The treatment of Al + NaHS reduced the Al content in rice seeds by
16.31% and 32.11% and increased the internal H2S content by 3.82%
and 8.90% at 3 and 5 d of treatment, respectively, compared with Al treatment. Al
+ NaHS treatment significantly increased the activities of superoxide dismutase
(SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and ascorbic
acid- glutathione (AsA-GSH) synthesis, and significantly reduced H2O2,
O2·̄ and malonaldehyde (MDA) contents in rice seeds at
3 and 5 d of treatment, compared with Al treatment. Al + NaHS treatment significantly
decreased the pectin content, inhibited pectin methyl esterase (PME) activity,
upregulated the expression of OsSTAR1/2 to reduce or mask Al-binding
sites in the cell wall, and inhibited the expression of Al transporter gene ONRAT1 to reduce Al uptake, compared
with Al treatment. The expression of the vacuolar Al transporter gene OsALS1 was significantly increased under
Al + NaHS treatment to promote the transport of cytoplasmic Al into the
vacuoles under Al toxicity conditions. In addition, compared with Al treatment,
the phytohormones zeatin, dihydrozeatin, gibberellin and auxin, which are
related to cell division and seed germination, were significantly increased under
Al + NaHS treatment.