Comparisons Of The Physiological Response And Resistant Mechanisms Of Main Landscpae Trees Tolerant To Cd Stress In Fuzhou

The reaction in growth,and physiology and biochemistry of Ficus microcarpa L.f,Cinnamomum camphora(L.) Presl,Mangifera indica Linn and the one-year -old seedlings to the stress of Cd were studied with the methods of solution and pot culture.Each species was treated with different concentration gradient,namely,0.3, 1,10 and 20 mg/kg(pure Cd²⁺) in turn,and meanwhile control group(CK) was set as well.The results were as follows:(1) The Cd treatment had an activation effect on the seed germination of these three tree species under low concentrations and an inhibition effect under high concentrations.The inhibition rate of embryonic root extension increased with the increase of Cd concentration,and the order was Cinnamomum camphora(L.) Presl＜Ficus microcarpa L.f.＜Mangifera indica Linn.In addition,the regressive relationship between Cd concentration and seed germination,and between Cd concentration and inhibition rate of the root was significant.(2) Under the stress of Cd,the cell permeability of Mangifera indica Linn increased,having an upward trend with the increase of the concentration;as for Ficus microcarpa L.f.and Cinnamomum camphora(L.) Presl,their cell permeability decreased when the concentration of Cd＜1 mg/kg,and increased with higher concentration,in addition,the increasing amplitude of Ficus microcarpa L.f.was bigger than Cinnamomum camphora(L.) Presl.(3) Under the stress of Cd,the photosynthetic systems of the 3 species were affected.The chlorophyll contents of the leaves and net photosynthetic rate of the seedlings of Mangifera indica Linn and Ficus microcarpa L.f.displayed a downward trend with the increase of Cd concentration,and the decreasing amplitude of Mangifera indica Linn was bigger than that of Ficus microcarpa L.f..While the chlorophyll contents of the leaves and net photosynthetic rate of the seedlings of Cinnamomum camphora(L.) Presl changed little.Besides,a/b values of these three tree species were all more than that of CK,however,the difference between a/b value and the concentration main effect was insignificant.(4) Under the stress of Cd,the free radical scavenging system was seriously affected.The activity of peroxidase(POD) and catalase(CAT) of Cinnamomum camphora(L.) Presl and Ficus microcarpa L.f.was stimulated to some extent by the Cd of low concentration,which showed that the two tree species had the capacity to prevent being hurt by Cd.However,their enzyme activity began to drop with the increase of concentration,which reflected that the capacity to resist Cd was limited.As for Mangifera indica Linn,its POD and CAT activity decreased under the stress of Cd.(5) Under the stress of Cd,the seedlings of Mangifera indica Linn were more slender and shorter,and had less biomass;while the root stem,seedling height and biomass of Cinnamomum camphora(L.) Presl changed more than Ficus microcarpa L.f.did,and Ficus microcarpa L.f.changed quite a little with the increase of Cd concentration.(6) According to the comprehensive evaluation by subordination function method,the stress-resistance to Cd of the three tree species was in the order of Cinnamomum camphora(L.) Presl＞Ficus microcarpa L.f.＞Mangifera indica Linn.With the seeds of three common evergreen broad-leaved tree species in Fuzhou and one-year-old seedlings as the test materials,their physiological and ecological effects on the stress of Cd with different concentrations were studied,and the differences in stress-resistance to Cd of different tree species were discussed and compared,besides,their capacity in stress-resistance to Cd was comprehensively evaluated as well in this paper,in order to provide theoretical basis for the selection of garden tree species in Fuzhou and thus the garden tree species could better play their part in improving the ecological environment.