遮阴胁迫下氮肥运筹对胡麻茎秆木质素合成及抗倒伏性的调控机制OA

To explore the regulatory mechanism of nitrogen fertilizer management under shading stress on lignin synthesis,stem components and lodging resistance of flax,a split-plot experiment with two factors of shading degree and nitrogen application rate was conducted using'Dingya 26'flax as the experimental material.The main plots were set at three light levels:natural light(S0),30%shading(S1),and 60%shading(S2);the subplots were set at three nitrogen application rates:pure N 0 kg·hm-2(N0),pure N 150 kg·hm-2(N1),and pure N 225 kg·hm-2(N2).The effects of shading and nitrogen application on the mechanical properties of flax stems,structural components,activities and gene expressions of lignin-related enzymes,and yield components were studied.The results showed that compared with natural light(S0),shading led to a decrease in the number of branches,seeds per capsule,capsules per plant,and 1 000-seed mass.The yields of flax under S1 and S2 levels decreased by 143.81 kg·hm-2 and 328.90 kg·hm-2,respectively.Meanwhile,the lodging resist-ance index and bending resistance of stems under S1 and S2 levels significantly decreased.This showed that the shading inhibited the lodging resistance of stems,and that the inhibition degree increased with the increase of shading degree.The application of pure N 150 kg·hm-2 significantly increased the activities of PAL,TAL,and CAD enzymes and the expression levels of 4CL1 and F5H3 genes un-der shading conditions,promoted lignin synthesis and increased cellulose content,and which mostly showed a trend of"first increase then decrease".Compared with the natural light level,the lodging resistance index under the S1N1 treatment varied between-13.49%to 35.29%.Compared with the shading treatment,the lodging resistance index significantly increased by 13.62%to 83.88%,accom-panied by a yield increase of 224.68 kg·hm-2 to 417.60 kg·hm-2.Correlation analysis indicated that the activities of lignin synthesis enzymes PAL,TAL,and CAD,the relative expression levels of 4CL1 and F5H3 genes,lignin and cellulose contents were significantly correlated with the bending re-sistance and lodging resistance index of stems.Therefore,under a low-light(shading)environment,the application of pure N 150 kg·hm-2 simultaneously enhances the lodging resistance and stabilizes the yield of flax by regulating the physiological and molecular processes of lignin synthesis and optimi-zing the structural components of stems.The study provides a precise nitrogen fertilizer management scheme for flax cultivation under low-light stress.