The Effects of an Exogenous Nitric Oxide on the Physiological Characteristics in Females and Males of Populus deltoides Exposed to Pb Stress

PurposeMore knowledge about sex-specific responses in physiology to NO is helpful to understand different responsive processes of dioecious plants to stressful environment.

MethodThe physiological effects of exogenous NO signalling molecule on males and females of Populus deltoides were analyzed by using pot culture experiment, in which two levels of Pb was set, i.e., 20.5 mg/kg (DW) and 100 mg/kg (DW).

Result(1) Under Pb stress, the contents of lead (Pb), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) in the leaves of males and females of P. deltoides increased significantly, and the females had a greater increase. However, the above parameters of both sexes decreased to different degrees when we added SNP, and the males decreased more greatly. (2) The activities of both glutathione reductase (GR) and peroxidase (POD), and proline (Pro) content in leaves of both sexes increased in varied degrees under Pb stress, and the addition of SNP could increase the Pro and soluble protein content in leaves of two sexes, the males showed a greater increase. (3) SNP could increase the activities of superoxide dismutase (SOD) and GR in males under Pb stress, but significantly reduced the activities of SOD and POD in females. (4) Pb pollution inhibited the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of both sexes of P. deltoides to some extent, and P_n and G_s of males were restored to a certain extent when SNP was added.

ConclusionThere were greater negative effects exerted by Pb pollution on females when compared to males, while the NO was beneficial to males by promoting the activities of antioxidant enzymes and content of proline, and then restored the gas exchange rate of males, whereas there was no obvious protective effect on females exerted by NO.