Salt Stress Affects the Growth and Yield of Wheat (Triticum aestivum L.) by Altering the Antioxidant Machinery and Expression of Hormones and Stress- Specific Genes

Understanding physiological responses in saline agriculture may facilitate wheat breeding programs.Based on a screening test,the Ningmai-14(NM-14)and Yangmai-23(YM-23)wheat cultivars were selected for further experiments to understand the underlying salinity tolerance mechanism.This study investigated the effects of five salinity levels such as Control(CK)=0(without NaCl stress),S1=0.20%,S2=0.25%,S3=0.30%and S4=0.35%of NaCl concentrations of soil on wheat plants.The results showed that increased salinity concentration reduced the growth and yield of wheat cultivars(NM-14 and YM-23).However,YM-23(12.7%)yielded more than NM-14 at maximum salinity stress.The higher salinity(S4)increased the concentration of Na^(+)(4.3 to 5.8-fold)and P contents(2.5 to 2.2-fold),while reducing the average concentrations of K^(+),Cu,and K^(+)/Na^(+)ratio.The higher salinity(S4)reduced the spikelet length by 21.35%(followed by grain spike−1),and the starch content by 18.81%.In the YM-23 cultivar,higher salinity increased superoxide dismutase(SOD),total antioxidant capacity(TAC),and amylase.Compared to NM-14,induced expression of TaYUC2,6,and TaGA13ox,20ox genes were recorded in YM-23.Similarly,in YM-23 the stress-specific genes such as TaHSP70,90 were enhanced whereas,TaSOS1,2 were suppressed.Overall,our study revealed that salt tolerant cultivars modulate hormonal and antioxidant activities,thus maintaining high growth.

Reduced nitrogen application rate with dense planting improves rice grain yield and nitrogen use efficiency: A case study in east China

Dense planting could be a feasible method for reducing nitrogen(N) application rates without compromising rice grain yield in northeast and central China. It is still unclear whether reduced N application with dense planting(RNDP) can achieve higher rice yield and N use efficiency(NUE) in Jiangsu, east China. Three japonica inbred rice(JI) and three indica hybrid rice(IH) cultivars were grown in a field experiment. Their grain yield, NUE, and related traits were compared under two cultivation treatments:conventional high-yielding practice(CHYP) and RNDP. JI showed similar yields under the two treatments,while IH showed lower yield under RNDP than under CHYP, and the partial factor productivity of N and N use efficiency for grain yield increased(P < 0.05) in both JI and IH under RNDP. Compared with CHYP,RNDP reduced spikelets per panicle but increased panicles per m2 and filled-kernel percentage of JI and IH, and JI's kernel weight was increased(P < 0.05) under RNDP. Shoot biomass weight and nonstructural carbohydrate(NSC) content in the stem at heading and maturity of JI and IH were reduced under RNDP, while harvest index and NSC remobilization reserve were increased(P < 0.05) under RNDP, especially for JI. Our results suggest that RNDP could achieve a higher rice grain yield and NUE, particularly for JI, a dominant rice cultivar type in Jiangsu. For JI, the increased panicles per m2, sink-filling efficiency, harvest index, and NSC remobilization after heading under RNDP contributed to a grain yield similar to that under CHYP.

Biochar-mediated Cd accumulation in rice grains through altering chemical forms,subcellular distribution,and physiological characteristics

Biochar can change the availability and morphology of soil Cd.However,the influence of biochar on Cd chemical form and subcellular fraction in rice is poorly understood,particularly under different irrigation methods.A pot experiment of biochar application combined with two irrigation methods(continuous flooding and intermittent irrigation,CF and Ⅱ)was conducted.The Cd accumulation,chemical form and subcellular fraction in rice organs and the associated physiological responses were examined.Biochar significantly reduced soil available Cd(30.85-47.26%and 32.35-52.35%)under CF and Ⅱ but increased the Cd content(30.4-63.88%and 13.03-18.59%)in brown rice.Additionally,the Cd content in shoots/grains under Ⅱ was higher than that under CF.Biochar elevated the Cd soluble fraction in roots while lowered the cell wall fraction under both irrigation methods,whereas the opposite result was observed in leaves.Biochar increased water-,ethanol-,and NaCl-extractable Cd in roots meanwhile increased ethanol-extractable Cd in leaves under both irrigation methods.Moreover,the total amount of water-,ethanol-,and NaCl-extractable Cd in rice roots was higher under Ⅱ than under CF.Related hormones and antioxidant enzymes may also be involved in biochar-mediated Cd accumulation in rice grains.Thus,changes in Cd chemical form and subcellular fraction in the root and leaf are the main mechanisms of biochar-induced rice grains Cd accumulation.