Abstract:

In order to explore the effect of salt stress on the physiological mechanism of cotton,saline-tolerant cotton Zhong J0710 was used as a control,two new cotton distantly hybrid germplasms HL2 and A₂H cultivated in cotton breeding research group were treated with salt solution for 15 d(concentration of 200 mmol/L)at seedling stage,and the relative plant height,relative root length and relative survival rate of the test materials were analyzed,and the salt damage index was calculated.The salt tolerance of the test materials was comprehensively evaluated by combining the measurement results of physiological indicators such as primary light energy conversion efficiency (Fv/Fm),antioxidant enzyme activity,proline content,and soluble sugar of seedlings at different treatment times (0,5,12,24,48 h).The results showed that after 15 d of salt stress,the damage degree of the growth of seedlings of the three test materials was as follows:Zhong J0710<HL2<A₂H,and salt stress significantly inhibited the relative plant height,relative root length and relative survival rate of A₂H,indicating that the salt concentration treatment had less effect on the growth and development of HL2 and Zhong J0710,but had a greater effect on A₂H.Under different treatment times,salt stress had different degrees of influence on the maximum light energy conversion efficiency of the three test materials,and the inhibition degrees from weak to strong compared with before stress were HL2<A₂H<Zhong J0710.Compared with the non-stress period, the peroxidase (POD) activity of the tested materials was increased by salt stress, and the POD activity of HL2 during the stress process was significantly higher than that of A2H and Zhong J0710 in the salt-tolerant control, and reached a very significant level at 12—48 h of stress,and the change law of superoxide dismutase (SOD) activity was not obvious,and the role in salt stress was low.The contents of proline in HL2 and the salt-tolerant control increased with the increase of salt stress time,and the soluble sugars and soluble proteins of germplasm HL2 were significantly higher than those in the salt-tolerant control and A₂H during the entire salt stress period.In summary,in salt adversity,salt-tolerant materials have a more developed root system;higher light energy conversion efficiency,higher reactive oxygen species clearance capacity in cells and higher accumulation of osmoregulatory substances are the physiological basis for strong salt tolerance.

Key words: Cotton, Seedling stage, Salt tolerance identification, Pattern indicators, Physiological indicators