This study investigated whether
uniconazole confers drought tolerance to soybean and if such tolerance is correlated with changes in photosynthesis,
hormones and
antioxidant system of leaves. Soybean plants were foliar treated with
uniconazole at 50 mg L-1 at the beginning of bloom and then exposed to water deficit stress at pod initiation for 7 d.
Uniconazole promoted biomass accumulation and seed yield under both water conditions. Plants treated with
uniconazole showed higher leaf water potential only in water-stressed condition.
Water stress decreased the
chlorophyll content and photosynthetic rate, but those of
uniconazole-treated plants were higher than the stressed control.
Uniconazole increased the maximum quantum yield of photosystemand
ribulose-1,5-bisphosphate carboxylase/
oxygenase activity of water-stressed plants.
Water stress decreased partitioning of assimilated 14C from labeled leaf to the other parts of the plant. In contrast,
uniconazole enhanced translocation of assimilated 14C from labeled leaves to the other parts, except stems, regardless of water treatment.
Uniconazole-treated plants contained less GA3, GA4 and ABA under well-watered condition than untreated plants, while the IAA and
zeatin levels were increased substantially under both water conditions, and ABA concentration was also increased under water stressed condition. Under water-stressed conditions,
uniconazole increased the content of
proline and soluble
sugars, and the activities of
superoxide dismutase and
peroxidase in soybean leaves but not the
malondialdehyde content or electrical conductivity. These results suggest that
uniconazole-induced tolerance to water deficit stress in soybean was related to the changes of photosynthesis,
hormones and
antioxidant system of leaves.