Effect of NaCl stress on the growth and physiological characteristics of broccoli
[Objective]The study aimed to explore the effects of NaCl stress on the growth and physi-ological characteristics of broccoli seedlings and the adaptive mechanism,laying a theoretical and technical basis for the cultivation of broccoli in saline-alkali soil.[Method]Six NaCl stress treatments were set up,i.e.,0 mmol/L(CK),100 mmol/L,200 mmol/L,300 mmol/L,400 mmol/L and 500 mmol/L,and the growth of broccoli and its related physiological indexes were dynamically measured.[Result]Compared with CK,the mild salt stress(100 mmol/L NaCl)increased the biomass,photosynthetic rate,stomatal con-ductance,transpiration rate,soluble sugar and soluble protein content of broccoli,and the malondialdehyde and relative conductivity of leaves decreased significantly in 6 d of stress.Six days after moderate salt stress(200～300 mmol/L NaCl),the leaf Fv/Fm,photosynthetic rate,stomatal conductance and transpiration rate of broccoli decreased significantly compared with CK,and intercellular CO2 concentration increased signifi-cantly.Leaf soluble sugar content and soluble protein content decreased gradually,and leaf malondialdehyde content and relative electrical conductivity showed an upward trend.In 9 d of NaCl treatment,MDA content and relative conductivity of Z3 treatment increased 73%and 65%,respectively,compared with CK.Under severe salt stress(400～500 mmol/L NaCl),the growth of broccoli was greatly inhibited,and leaf soluble sugar content and soluble protein content decreased continuously,and photosynthetic rate of broccoli was significantly reduced by 55%～92%in 3 d～12 d of salt stress.[Conclusion]The mild NaCl treatment pro-moted the growth of broccoli,enhanced photosynthetic capacity,increased the content of soluble sugars and soluble proteins in leaves,and maintained the cellular osmotic potential.The moderate NaCl treatment for root inhibited the growth of broccoli and reduced leaf photosynthetic capacity.The strong NaCl treatment for root severely inhibited the growth of cycads,reduced photosynthetic capacity,soluble sugar and soluble protein contents,even led to plant death.
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