| Aluminum(Al) is believed to be one of the major factors limiting the growth of roots and the overall development of plants in acid soils. So the researches on Al resistant mechanism are of great importance. In the study, four watermelon (Citrullus lanatus) varieties chaotiandileiwang (DL), zaojia84-24 (ZJ), zaomiwang (ZM) and zaochunhongyu (HY) seedlings were used as materials to investigate the effect of aluminum(Al) on growth and physiological characteristics under different Al concentrations (0,250,500, 1000,1500μmol·L-1) stress. The results showed that Al treatment significantly decreased the root length, root vigor and dry weight of ZM, while the growth of H Y was almost not affected or promoted by Al. The influence of ZJ and DL were between that of ZM and HY. So ZM was more sensitive to Al than HY. Therefore, the ZM and HY were selected to further study the changes of physiological characteristics under Al stress. The results revealed that Al stress increased the plasma membrane permeability and malondialdehyde(MDA) content in ZM and HY leaves. In condition of Al3+<1000umol·L-1, the breakage of HY membrane system was recovered at a certain level with extending the treatment time, In addition, the Pro content, the activities of supper oxide dismutas (SOD) and Peroxidase (POD) were also increased; while catalase (CAT) activity was almost not affected by Al. So there was some difference between ZM and HY when response to Al stress. HY had a better physiological mechanism than ZM to respond to Al stress and Proline (Pro) content and SOD, POD activites were closely related to Al tolerance ability of watermelon.Effects on photosynthesis for the followed three aspects:1) Chlorophyll content of HY increased in the Al treatment. Chlorophyll content of ZM was higher than contrast only when Al concentration was 250μmol·L-1. Chlorophyll a/b content of HY intended to decrease as long as the Al concentration increased.2) In the Al treatment, when concentration lower than 500μmol·L-1 the stomatal conductance (Gs), intercellular CO2 concentration (Ci), net photosynthetic rate (Pn) and transpiration rate (Tr) of ZM was effected more obviously than those of HY. When Al concentration was above 1000μmol·L-1, the value of these four items all intended to fall down.3) Changes of Chlorophyll Fluorescence in these two watermelon variety in the Al treatment were as follow:original fluorescence (Fo), maximum fluorescence (Fm), potential photochemical efficiency (Fv/Fo), photochemical maximum efficiency of PSII (Fv/Fm) and the ability of leaves to transform energy (YII) decreased, while non-photochemical quenching (NPQ) increased, and leaves maintained a high actinic light energy distribution by adjusting the heat dissipation; In addition, photochemical quenching coefficient (qP) and electron transport rate (ETR) decreased. At Al3+≤250umol·L-1 concentration, the four parameters of HY:Fo, Fm, Fv/Fo, Fv/Fm is more stable; with aluminum concentration increases, the electron transfer rate was less affected, NPQ relatively constant, that is able to maintain a constant light protection.Effects on rhizosphere micro-ecology showed:with the increased of Al concentration, in both rhtizosphere of HY and ZM, the number of bacteria were increased firstly and then decreased; the number of fungi were increased; the number of actinomycetes were decreased at day 7, with the extension of time, the number of actinomycetes were intended to increased first and then decreased at day 21. At day 7, the activity of catalase and invertase of HY were decreased with the increased of Al concentration, the activity of urease was increased first and then decreased; with the extension of time, the activity of catalase and invertase returned to normal level in lower Al concentration, but significantly lower than the control in higher Al concentration; the activity of urease were decreased with the Al concentration. With the increased of Al concentration and extension of time, the activity of catalase, invertase and urease were decreased. |
PDF Full Text Request