不同水分条件下春小麦根系耗碳及其与产量形成的关系

CARBON CONSUMPTION OF ROOTS AND ITS RELATIONSHIP TO YIELD FORMATION IN SPRING WHEAT AS AFFECTED BY SOIL MOISTURE

在自动控制的遮雨棚中 ,用盆栽法研究了不同水分条件下春小麦 (Triticumaestivum)根系耗碳过程及与籽粒产量的关系。设高 (W)、中 (M)、低 (S) 3个水分处理 ,试验品种为‘陇春 81 39_2’(L)和‘定西 2 4’(D)。在开花期及之前 ,根系的日生物量碳、日呼吸耗碳和日分泌耗碳量占根系日总耗碳量的比例平均为 2 6 %、5 8%和 1 6 %。在成熟期 ,W、M处理的根日生物量碳的下降 (负值 )在两品种之间没有显著差异 ,而在S处理中 ,D品种根生物量碳日下降幅度显著高于L品种 ,日呼吸耗碳量和日分泌耗碳量也最低 ,致使其根日生物量碳下降超过根总耗碳量的 1 0 0倍 ,而根日呼吸耗碳量和日分泌耗碳量分别是根日总耗碳量的 7.89倍和 3.75倍 ,与其它处理 /品种形成了鲜明对比。以根系日呼吸和日分泌耗碳之和占日光合固碳量的百分比来看 ,L品种在W、M和S处理中分别为 5 3%、5 2 %和83% ,D品种分别为 5 8%、4 9%和 5 5 %。两个品种根系碳消耗比例最低的是M处理 ,S处理的D品种远低于L品种。两品种产量水平接近 ,湿润条件下 ,L品种产量略高于D品种。籽粒产量与平均产量之比 (Y/Ym)L品种在 3个处理中分别为 1 .34,1 .1 4和 0 .5 3;D品种分别为 1 .0 4 ,1 .0 6和 0 .90。干旱条件下D品种保持了良好的产量稳定性。对D品种而言 ,中?

A potted plant experiment was conducted under an auto_rain_shelter to investigate C consumption of roots and its relationship to yield formation of spring wheat ( Triticum aestivum ) as affected by soil moisture. Two cultivars of plants, `Longchun 8139_2' (L) and `Dingxi 24' (D), were grown in a split PVC pot 100 cm long and 10 cm in diameter in a mixture of deep loessial soil and vermiculite (1∶5.2 g/g). Three soil water treatments were employed: wet (W, 75%-85% of field water capacity); medium drought (M, 45%-55% of field water capacity); and serious drought (S, 25%-35% of field water capacity). Water regimes were controlled by watering every 5 days and destructive sampling was performed at jointing, anthesis and mature stage to measure plant biomass in shoots and roots. Respiration in roots and rhizosphere was measured by infrared gas analysis system at these stages. Root exudation was calculated from the rhizosphere respiration. Of the total carbon consumed by roots during jointing and anthesis, 26% of daily C consumption was allocated to root biomass, 58% to root respiration and 16% to root exudation, when averaged across all treatments. During the maturing period, no significant differences in the daily decrease of C allocated to root biomass in the W and M treatments were found between the two cultivars, but, in the S treatment, the daily decrease of C allocated to root biomass was significantly more in D cultivars than in L, and the lowest daily C consumption from root respiration and exudation also occurred in D cultivars in the S treatments. This resulted in a greater than 100 times reduction in the ratio of root biomass C to total C invested in roots, and a 7.89 times and 3.37 times decrease in the ratio of root respiration C and exudation C to total C consumption, which was very different from other treatments/cultivars. The ratio of the sum of root respiration C and exudation C to total C consumption was 53%, 52% and 83% respectively for W, M and S treatments in L cultivars, and 58%, 49% and 55% in D cultivars. The lowest ratio occurred in the M treatment for both cultivars, and this ratio was far lower in D cultivars than in L for the S treatment. Grain yields were similar for both cultivars, but a little higher in L than in D under wet conditions. The ratio of grain yields of individual treatments to the mean yield of the three treatments was 1.34, 1.14 and 0.53 for W, M and S treatments in L cultivars, and 1.04, 1.06 and 0.90 in the three treatments of D cultivars. This suggests a higher stability of grain yields in D than in L cultivars. The decrease in daily C consumption of roots and the relative stabilization of daily photosynthetic rates accounted for the higher water use efficiency and relatively high grain yields under conditions of medium soil moisture.