Modified non-rectangular hyperbola equation with plant height for photosynthetic light-response curves of Potentilla anserina and Elymus nutans at various growth phases in the Heihe River Basin, Northwest China

The non-rectangular hyperbola(NRH)equation is the most popular method that plots the photosynthetic light-response(PLR)curve and helps to identify plant photosynthetic capability.However,the PLR curve can't be plotted well by the NRH equation at different plant growth phases due to the variations of plant development.Recently,plant physiological parameters have been considered into the NRH equation to establish the modified NRH equation,but plant height(H),an important parameter in plant growth phases,is not taken into account.In this study,H was incorporated into the NRH equation to establish the modified NRH equation,which could be used to estimate photosynthetic capability of herbage at different growth phases.To explore photosynthetic capability of herbage,we selected the dominant herbage species Potentilla anserina L.and Elymus nutans Griseb.in the Heihe River Basin,Northwest China as the research materials.Totally,twenty-four PLR curves and H at different growth phases were measured during the growing season in 2016.Results showed that the maximum net photosynthetic rate and the initial slope of PLR curve linearly increased with H.The modified NRH equation,which is established by introducing H and an H-based adjustment factor into the NRH equation,described better the PLR curves of P.anserina and E.nutans than the original ones.The results may provide an effective method to estimate the net primary productivity of grasslands in the study area.

沙地节水莲-渔共作对莲藕生长发育、品质的影响及效益评价

研究了不同莲-渔共作的生态种养模式对莲藕的生长发育、产品商品性、营养品质及经济效益的影响。结果表明,莲-渔共作模式有利于莲藕的生长发育和营养品质的提升。其中,T1莲-鳅共作模式处理表现最好,其莲藕根状茎的全藕质量、主藕质量、最大藕节质量分别为1.58 kg、1.39 kg和423 g,与对照相比分别提高了29.5%、36.3%和6.3%;在莲藕根状茎营养品质方面,T1处理莲藕产品的粗蛋白、淀粉、还原糖、粗纤维、维生素C含量均高于其他处理及对照,T1处理莲藕产品的氨基酸总量低于其他共生处理而高于对照,T1处理莲藕产品的硝酸盐含量低于其他共生处理并显著低于对照;在效益方面,T1处理增产效益最高,达97180元·hm^(-2),比对照增加64000元·hm^(-2),T2莲-小龙虾共作模式与T4莲-大闸蟹共作模对莲藕幼芽破坏较大,造成莲藕产量降低,但这2个处理的水产品产值较高,弥补了莲藕产量的产值损失,其经济效益均高于对照,而T3莲-鲤共作模式处理的增产效益最小,也比对照增加31940元·hm^(-2)。综上所述,沙地节水莲-渔共作模式中以T1处理表现最佳,值得在生产中推广应用。