Effect Of Cadmium Pollution And Salinization On The Growth And Physiology Of Male And Female Populus Deltoides

Soil cadmium pollution and salinization have become two noticeable problems of soil ecology in nowadays,which seriously threaten human health and the developments of agriculture and forest.It's found that the middle and lower reaches of Yangtze River,the most rapidly developing area of industry and agriculture in China,have been suffered from heavy metal cadmium pollution and soil salinization meanwhile.Populus deltoides featured with rapid growth,excellent timber quality,outstanding stress tolerance,thus it has been introduced and cultivated widely in the middle and lower reaches of Yangtze River,and plays a significant role in water and soil conservation and ecological restoration in this region.We designed a pot experiment to study the variations of the growth and morphology,the accumulation and allocation of biomass,photosynthetic capacity,antioxidant ability and toxic ions accumulation of males and females Populus deltoides under the treatment of combined stress of salt and cadmium.This experiment can help us to learn about the physiological mechanisms of male and female Populus deltoides resisted by the combined stress of cadmium pollution and salinization,and provide some theoretical foundations for the promotion and cultivation,breeding and the genetic improvement of Populus deltoides in areas where affected by the combined force of cadmium pollution and salinization.The major results and conclusions show as follow:1)Male Populus deltoides affected less influence by the cadmium-only treatment,the salt-only treatment and the salt-cadmium treatment than the female.The cadmium-salt treatment leads to a heavier damage on the accumulation and allocation of biomass and the growth rate of plants than the cadmium-only treatment and the salt-only treatment.There is a remarkable reduction of the males and the females growth,especially the females.2)The cadmium-only treatment,the salt-only treatment and the salt-cadmium treatment have different degree inhibiting effects on the pigment content and the photosynthetic rate in males and females Populus deltoides leaves,and the salt-cadmium treatment play a more significant influence than the cadmium-only treatment and the salt-only treatment.Comparing with the male,the female suffers from more negative impact,has weaker tolerance and gets more damage from the three treatments.Meanwhile,in order to release the injury from salt stress,the stomatal conductances and the transpiration rates of male and female Populus deltoides leaves are reduced,but there's no conspicuous difference between different sex.3)The cadmium-only treatment,the salt-only treatment and the salt-cadmium treatment promote the malonaldehyde content in the leaves of male and female Populus deltoides.The salt-cadmium treatment causes a more remarkable effect than the cadmium-only treatment and the salt-only treatment and the malonaldehyde content in the male leaves is less than the female under the three treatments.4)Contrasting the male,the activation of the antioxidant enzymes activities in female Populus deltoides leaves is more obvious under the cadmium-only treatment and the salt-only treatment.Due to the higher toxic ions concentrations in the leaves under the salt-cadmium treatment,the activities of antioxidant enzymes in male reveals a upper level,but the superoxide dismutase activity are restricted for the inactivation caused by cadmium ions.At the same time,the malonaldehyde content in females leaves increases as a result of the antioxidant enzymes activation changing under the salt-cadmium treatment.5)Under the salt-cadmium treatment,the sodium ions and cadmium ions show a synergistically improving role mutually.The increasing of sodium ions content in male and female Populus deltoides promotes the cadmium ions transfer to leaves,and so does the cadmium ions content increasing.The synergisticall improving capacity of cadmium ions and sodium ions act a superior part on male and female respectively.From the above,although the male Populus deltoides accumulates a larger amount of cadmium ions under the salt-cadmium treatment than the female,the negative effects on the growth,photosynthetic rate and oxidative stress of male Populus deltoides isn't more prominent.The male Populus deltoides is equipped with more considerable tolerance and resistance,and the female is more sensitive to cadmium and salt stress.Therefore,it's suggested that the planting range of the male Populus deltoides is supposed to be enlarged for better effect on the area suffering from cadmium pollution and salinization seriously.