Abscisic acid (ABA) plays a key role in drought. Non-photochemical quenching (NPQ), as a photoprotective mechanism, also plays an important role in different adversities. Although this mechanism is relatively understood, the relationship between ABA synthesis and NPQ induction under drought remains poorly defined. To understand the role of ABA in the mechanism underlying the photosynthetic response to drought, two rice cultivars with different chlorophyll contents were exposed to drought and exogenous ABA. Drought significantly stimulated the accumulation of endogenous ABA in leaf, and the application of exogenous ABA under drought further stimulated it through the up-regulated expression of the genes encoding 9′-cis-epoxycarotenoid dioxygenase. The application of exogenous ABA triggered higher NPQ under drought, especially in Zhefu802. The expression of PsbS1 was significantly increased by drought, while the expression of PsbS1 was further up-regulated by spraying ABA under drought. However, the high zeaxanthin content was not further up-regulated by spraying ABA under drought. These results indicated that ABA increased the expression of PsbS1 and further triggered NPQ as a strategy to decrease the overexcitation of the photosynthetic apparatus in rice. This phenomenon was validated by slowing the decrease of the net photosynthetic rate under the application of exogenous ABA in the two rice cultivars. Except for the regulation of photoprotection, exogenous ABA significantly decreased the malondialdehyde level in Zhefu802 and the H₂O₂ level in Fgl. In conclusion, exogenous ABA significantly increases endogenous ABA and then triggers NPQ to mitigate the inhibition of photosynthesis in drought.

脱落酸（ABA）在干旱中起着关键作用。非光化学猝灭（NPQ）作为一种光保护机制，在不同的逆境中也发挥着重要作用。尽管这一机制相对较清楚，但干旱条件下 ABA 合成与 NPQ 诱导之间的关系仍不清楚。为了了解 ABA 在光合干旱响应机制中的作用，将两个叶绿素含量不同的水稻品种暴露于干旱和外源 ABA 下。干旱显着刺激了叶片内源ABA的积累，干旱条件下施用外源ABA通过上调9'-顺式环氧类胡萝卜素双加氧酶基因的表达进一步刺激了叶片内源ABA的积累。施用外源ABA会在干旱条件下引发较高的NPQ，尤其是浙富802。干旱使PsbS1的表达量显着增加，而干旱条件下喷洒ABA进一步上调PsbS1的表达量。然而，干旱条件下喷洒ABA并没有进一步提高玉米黄质的高含量。这些结果表明，ABA 增加了PsbS1的表达，并进一步触发 NPQ，作为减少水稻光合机构过度兴奋的策略。通过减缓外源 ABA 作用下两个水稻品种净光合速率的下降，验证了这一现象。除了光保护的调节外，外源ABA显着降低了Zhefu802中的丙二醛水平和Fgl中的H ₂ O ₂水平。总之，外源ABA显着增加内源ABA，然后触发NPQ来减轻干旱对光合作用的抑制。