Abstract:

Forage rapeseed is an important cash crop and can grows under salt stress. In order to explore the regulatory effect of nitrogen （N） on the accumulation of organic osmoregulation substances for forage rapeseed under salt （NaCl） stress， we selected one cultivar （Hua You Za No. 62） and designed a pot experiment for this purpose. The plot experiment includes four NaCl stresses （0， 2， 4， or 6 g·kg^-1） and four pure N levels （0， 120， 240， 360 kg·ha^-1）. Five physiological indexes， including leaf water content and contents of malondialdehyde （MDA）， proline， soluble sugars， chlorophyll and total N in the leaves were measured and used to evaluate this effect of N. The results showed that the growth of forage rapeseed was significantly inhibited under salt stress. The contents of MDA and organic osmotic regulating substances （proline and soluble sugars） increased with increasing salt content in the soil， while the leaf water content， the contents of chlorophyll and total N decreased. The contents of proline and soluble sugars were significantly higher and the MDA content was significantly lower under the 240 kg·ha^-1 N level. The higher level of N supplementation （360 kg·ha^-1） resulted in significant decreases of the leaf water content， MDA content and soluble sugars content， while significant increases the contents of chlorophyll and total N. The principal component analysis for five growth stages showed that N significantly affected the contents of MDA， proline， chlorophyll， and total N at the early growth stage， but significantly affected the leaf water content and soluble sugars content at later growth stages. In conclusion， appropriate N supplementation can promote the accumulation of organic osmoregulation substances and weaken the adverse effects of salt on the growth of forage rapeseed.

Key words: salt stress, nitrogen, rape, osmotic adjustment