| Exogenous substances are now the most effective,economic,practical and feasible way to improve plant resistance to copper stress.Ca2+ played a significant role in plant adversity,we have obtained that Ca2+ could improving plant resistance in the study of salt stress,low temperature stress,etc,and it’s effects was closely related to the added exogenous Ca2+ concentration.But which Ca+2 concentration plays a role of easing stress and its relationship with plants’ resistance to Cu2+ under copper stress is still remains unclear.Therefore,this thesis took ’farmers 85 days’ cauliflower as material,used hydroponic way,studied the effects of different concentration of copper(0,5,10,15,20mg/L)on morphological and physiological characteristics of cauliflower seedlings leaves and roots’ and then studied the restoring effect of Ca2+(0,5,10,20,40mmol/L)on reliefing copper poisoning,found out the best calcium concentration based on this research;Studied the effects of two different calcium agents EGTA,LaC13 and Ca2+on growth,physiological characteristics of cauliflower under copper stress,so as to explore the pathophysiological role and regulatory mechanism of Ca2+-CaM in cauliflower under copper stress.Put forward to effective methods to alleviate copper poison damages,improve the plants’ resistances and adapts to adversity,provide theoretical basis for improving planting technology and resistance breeding,rationally used of pesticide and fertilizer of cauliflower.The results are as follows:1.Physiological response of cauliflower seedlings to copper stressCopper concentration≦ 10mg/L had a little effects on the growth of cauliflower;Copper concentration≧15mg/L inhibited the growth of cauliflower,underground and aboveground dryweight accumulation dropped rapidly,shorten the length of root and decreased plant height.High concentration copper made chlorophyll content of cauliflower seedlings reduced,increased free proline(Pro),soluble sugar,soluble protein and malondialdehyde(MDA)content,increased cell relative membrane permeability,changed super oxide dismutase(SOD),peroxidase(POD),catalase(CAT)activity,the roots showed the same change trends.For the same index,the responses of roots were more sensitive to copper,low concentration of copper can produce toxic to cauliflower roots.Results showed that when the copper concentration was more than 15mg/L could cause obvious poison of cauliflower leaves and roots.2.Effects of different concentrations of Ca2+ on growth and chlorophyll content of cauliflower seedlings under copper stress.Compared with pure copper stress,10mmol/L Ca2+ treatment could obviously promoted the growth of cauliflower under copper stress,increased fresh and dry weight of aboveground and underground parts,promoted root elongation,increased plant height,slowed down growth inhibition of cauliflower under copper stress;But different concentrations of exogenous Ca2+ caused little effect on the chlorophyll content of cauliflower under copper stress.Showed that appropriate concentration of exogenous Ca2+ can relieved Cu2+ stress,but it doesn’t work on the recovery of chlorophyll content in leaves reduced caused by copper poison.3.Effects of different concentrations of Ca2+on the changes of osmotic regulation substances in different ways of cauliflower seedlings under copper stress.Roots and leaves soluble protein,soluble sugar,Pro content increased to different extent of cauliflower under copper stress,10mmol/L exogenous Ca2+ treatments could obviously increase soluble sugar,soluble protein and pro contents of cauliflower leaves and roots.Ca2+ signaling system affect the process of synthesis of copper osmotic regulation substances in cauliflowers.4.Effects of different concentrations of Ca2+on membrane lipid peroxidation and protective enzyme activity changes of cauliflower seedlings under copper stress.10mmol/L Ca2+could obviously reduced the membrane injury rate of cauliflower leaves and roots,membrane lipid peroxidation products MDA content;Ca2+participated in reactive oxygen produce and clear in cauliflower under copper stress,copper stress coud increased super oxygen anion free-radical(O2-)producing rate H2O2 contentof cauliflower,10mmol/L Ca2+ treatment could alleviate the effect of copper stress by obviously reducing the accumulation of reactive oxygen metabolic,reduce its damage of membrane system;but also improve the protective enzyme,the activity of SOD,POD.Effect of high Ca2+concentration on relief the enzyme activity was reduced,membrane damage and MDA accumulation caused by copper poison was not obvious,and when the concentration reached 40mmol/L it coulde increased the harms of plant insteaded.Ca2+ involved in cauliflower copper resistance to copper stress environment by regulating membrane lipid peroxidation and protective enzyme activity.5.Effects of Ca2+ and different calcium inhibitors on the growth,active oxygen metabolism,changes in the activity of protective enzyme of cauliflower under copper stress.Compared with 10mmol/L Ca2+,EGTA or LaC13 treatment significantly inhibited the growth of plants,root elongation,aggravate the damage of membrane system and reduce the activity of protective enzyme,shwed that aboveground growth slowing,root growth,protective enzyme activity,osmotic regulation substances content reduce,H2O2 and MDA content increased;the physiological inhibitory effect on plant of LaCl3 was greater than the EGTA under copper stress.EGTA and LaC13 inhibited the growth of plants and physiological activity by inhibiting the Ca2+-CaM signal system which played a role of easing copper stress.Results showed that adding exogenous Ca2+alleviated cauliflower Cu2+stress by promoting or stimulating the Ca2+-CaM system,EGTA and LaC13 eliminated mitigation effects of Ca2+ by inhibiting the Ca2+-CaM signal system,confirmed that cauliflower Cu2+stress relief was caused by a suitable concentration of exogenous Ca2+. |
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