合理施磷量提高水稻拔节期对大气增温的抵御能力

Optimizing phosphorus application rate to enhance rice resistance to elevated atmospheric temperature at the jointing stage

【目的】磷素(P)在水稻抗逆性方面有重要作用,我们研究了磷素供给水平对大气增温条件下水稻光合效率、养分吸收以及生长发育的影响,为应对气候变化提供养分管理措施。【方法】本研究选用‘陵两优268’(籼型两系杂交稻)作为研究对象,进行盆栽模拟试验。试验设常温对照和增温1.5℃两个温度条件,增温通过红外加热器(MR-2420)进行。每个温度下设置5个磷素(P_(2)O_(5))施用水平:0、30、60、90及120 mg/(kg,土),依次记为P_(0)、P_(30)、P_(60)、P_(90)、P_(120)。在水稻拔节期,测定叶片光合特征参数、养分含量和生物量。【结果】除常温条件下,P_(90)磷水平的水稻叶片胞间CO_(2)浓度(C_(i))出现最小值外,水稻叶片的净光合速率(P_(n))、气孔导度(Gs)、蒸腾速率(T_(r))和C_(i)均在P_(90)磷水平出现最大值。等施磷量下与常温相比,增温显著提高了P_(0)、P_(30)、P_(60)处理的Gs和T_(r),而对P_(90)处理的Gs和P_(120)处理的T_(r)没有显著影响;增温显著提高P_(90)和P_(120)处理的地上部磷含量,以及P_(0)和P_(120)处理的根部磷含量;增温提高P_(60)和P_(90)处理地上部和根部氮含量;增温提高P_(30)处理的地上部钾含量而对其根部钾含量无显著影响。常温和增温条件下,水稻生物量和分蘖数均在P_(90)达到最大值,增温显著提高了P_(30)和P_(60)处理的根部生物量,而显著降低了等磷处理下的地上部生物量以及P_(0)和P_(90)处理的总生物量。通径分析结果表明,在常温条件下,水稻生物量的最大影响因素为光合作用(P_(n)=0.554),其次为磷和氮吸收量,氮磷影响为直接作用,通径系数分别为0.309和0.308。增温条件下,水稻生物量的最大影响因素是磷(P_(TP)=0.794),其次为氮和光合作用,且二者通过磷产生间接作用,间接通径系数分别为0.547和0.528。【结论】合理施用磷肥是维持水稻光合效率和生物量的重要因素。江苏稻区的合理磷肥(P_(2)O_(5))用量约为110 kg/hm^(2),该施磷量下,水稻拔节期光合能力强,养分吸收量大,生物量也达到最高值,还可抵消增温对光合效率的不利影响,增加根部生物量,为后期水稻生产打下基础。因此,维持合理稳定的施磷水平是水稻抵御气候变暖不利影响的有效措施。

【Objectives】Phosphorus(P)plays an important role in stress tolerance of rice.We studied the effect of phosphorus supply levels on rice photosynthetic efficiency,nutrient absorption and growth,to find nutrient management for the adaptation of rice production to climate change.【Methods】A pot experiment was conducted using rice cultivar‘Lingliangyou 268’,an indica two-series hybrid rice,as test material.Two growth temperature conditions were provided,one was the local ambient temperature(aT),and the other was 1.5℃elevated temperature(eT)by infrared heater(MR-2420)above the rice plants.Under each air condition,five P_(2)O_(5)application rates of 0,30,60,90 and 120 mg/kg were setup,denoted as P_(0),P_(30),P_(60),P_(90) and P_(120).Leaf photosynthetic characteristics parameters,nutrient content and biomass were measured at the rice jointing stage.【Results】The net photosynthetic rate(P_(n)),stomatal conductance(Gs),transpiration rate(T_(r)),and intercellular CO_(2)concentration(C_(i))of rice leaves were all maximized,except for the minimum value of C_(i) in P_(90) treatment under ambient condition.Compared to aT in the same P application rate,eT significantly increased Gs and T_(r)in P_(0),P_(30),and P_(60) treatments,did not on Gs in P_(90) and T_(r)in P_(120) treatment.eT increased shoot P content in P_(90) and P_(120) treatments and root P content in P_(0) and P_(120) treatments,enhanced shoot and root N content in P_(60) and P_(90) treatments,elevated shoot K content in P_(30) treatment but did not significantly affect root K content.Under both aT and eT condition,the highest shoot,root and total biomass of rice were appeared in P_(90),which were significantly higher than in the other treatments.In the same P application rate,eT increased the root biomass in P_(30) and P_(60),decreased shoot biomass in all the P treatments and total biomass in P_(0) and P_(90) treatments.The results of the pathway analysis showed that under aT conditions,the greatest influence of rice biomass was photosynthesis(P_(n)=0.554),followed by P and N uptake,and the influence of N and P was direct,with the pathway coefficients of 0.309 and 0.308,respectively.Under eT condition,the greatest influence of rice biomass was P(P_(TP)=0.794),followed by N and photosynthesis,and the two had indirect effects through P,with the indirect pathway coefficients of 0.547 and 0.528,respectively.【Conclusions】Suitable P application rate is the key factor for maintaining high photosynthetic efficiency and biomass of rice.In the rice production of Jiangsu Province,applying 110 kg/hm^(2)of P fertilizer could achieve high photosynthetic efficiency,nutrient uptake and biomass of rice,enhance the tolerance to climate warming by keeping or increase root biomass at jointing stage of rice,and lay the foundation for rice production in the later stages of the season.Therefore,maintaining a reasonable and stable level of phosphorus application is an effective measure for rice to withstand the adverse effects of climate warming.