Effects of the potassium application rate on lipid synthesis and eating quality of two rice cultivars

Lipid content has an important effect on rice eating quality,but the effects of fertilizer application rate on the lipid synthesis and eating quality of rice are not well understood.Potassium(K)has a strong influence on rice quality and the requirement for K fertilizer in rice is greater than for nitrogen(N)and phosphorus(P)fertilizers.To investigate the effects of K fertilizer on the lipid synthesis and eating quality of rice,we used Nanjing 9108(NJ9108,japonica)and IR72(indica)rice as experimental materials and four K levels:K0(0 kg ha^(-1)),K1(90 kg ha^(-1)),K2(135 kg ha^(-1))and K3(180 kg ha^(-1)).The results showed that the lipid content,free fatty acid(FFA)content,unsaturated fatty acid(UFA)content,malonyl-CoA(MCA)content,phosphatidic acid(PA)content,lipid synthesis-related enzyme activities and eating quality first increased and then decreased with increasing K in both cultivars.The maximum values were obtained under K2.However,the saturated fatty acid(SFA)content showed the opposite trend.No significant differences were found in pyruvate(PYR)content among the K treatments.The protein and oxaloacetic acid(OAA)contents and phosphoenolpyruvate carboxylase(PEPCase)activity of NJ9108 first decreased and then increased with increasing K,and the minimum values were obtained under K2;while IR72 showed the opposite trend and the maximum values were obtained under K1.Overall,increasing K optimized the fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis.The optimal K application rate for lipid synthesis,eating quality and grain yield was 135 kg ha^(-1)for both cultivars.

Screening of the Optimal Potassium Fertilization Rate for Maximizing Bulb Yield and Potassium Nutrient Evaluation in Fritillaria thunbergii Miq.

Background:The dry bulb of Fritillaria thunbergii Miq.is a traditional Chinese medicine,and is the leading product of the geo-authentic crude drugs‘Zhebawei’in Zhejiang Province.Fritillaria thunbergii requires more potassium(K)than nitrogen and phosphorus,while the response of F.thunbergii to K has rarely been studied.Objective and Methods:To evaluate the K nutritional status of F.thunbergii,a 2-year field experiment was conducted under six K application rates(0,40,80,120,160,and 200 kg K_(2)O ha−1)with two F.thunbergii cultivars(ZB1,narrow-leaf;ZB2,broad-leaf).Results:The bulbus Fritillariae Thunbergii(BFT)yield increased to a plateau with more than~120 kg K_(2)O ha-1.The BFT quality met the standard of Pharmacopoeia of P.R.China with more than 40.0 kg K_(2)O ha^(-1).Leaf K concentration was significantly correlated with BFT yield,and was more sensitive to K application rate as compared to those of stems and flowers.Potassium application extended the duration of rapid leaf-biomass accumulation and increased the accumulation rate.Two cultivars had similar response patterns to K application,but ZB2 had higher K partial productivity,leaf-biomass,and leaf K concentration than ZB1.Conclusion:108.4-128.0 kg K_(2)O ha^(-1) was the optimal K application range for BFT yield.The potassium nutrition index(KNI)model established based on leaf K concentration has biological significance and can be used for dynamic diagnosis of K nutritional status of F.thunbergii with both accuracy and simplicity.