不同生育时期遮光对马铃薯光合特性和产量的影响

为了研究不同生育时期遮光对马铃薯光合特性和产量的影响,明确马铃薯不同生育时期对弱光的耐受性,对2个马铃薯品种(‘冀张薯12号'和‘冀张薯8号')进行了4个生育时期(苗期、苗期至现蕾期、现蕾期至开花初期、开花初期至收获期)和3个遮光度(不遮光对照、20%遮光率和50%遮光率)的处理试验。结果表明: 与不遮光处理相比,20%遮光率下,2个品种马铃薯苗期SPAD值显著降低,苗期至现蕾期、现蕾期至开花初期SPAD值无显著变化,开花初期遮光15 d可使SPAD值呈一定程度增加;50%遮光率下,2个品种马铃薯SPAD值变化趋势与前者相同,除开花初期增幅加大外,其他生育时期变化幅度接近。各时期遮光对马铃薯叶片气孔导度(g_s)影响不大,除50%遮光率下‘冀张薯8号'叶片g_s在开花初期较对照显著降低43.9%外,其他处理的g_s与对照均无显著差异。遮光后叶片胞间CO₂浓度(C_i)呈增加趋势,苗期、苗期至现蕾期50%遮光可使C_i显著增加,其余各时期的C_i无显著变化。4个时期遮光处理的叶片净光合速率(P_n)均降低,2个品种马铃薯叶片P_n在50%遮光处理下的降幅均大于20%遮光处理,‘冀张薯12号'除在苗期遮光处理的叶片P_n降幅大于‘冀张薯8号'外,其余时期的降幅均小于‘冀张薯8号'。4个时期遮光使马铃薯产量均降低,且50%遮光处理降幅大于20%遮光处理。‘冀张薯12号'在苗期不耐弱光,其余时期的耐弱光能力优于‘冀张薯8号'。综合分析表明,耐弱光能力强的品种遮光处理后,叶片P_n和g_s降幅小、C_i增幅小,产量降幅也小。

Effects of shading on photosynthetic characteristics and yield at different growth stages of potato.

We examined the effects of shading photosynthetic characteristics, yield, and tolerance to low light in two potato varieties (Jizhangshu 12 and Jizhangshu 8) at four growth stages (seedling, seedling/budding, budding/early flowering and flowering/harvest). There were three shading treatments (0(CK), 20% and 50%). The results showed that at both 20% and 50% shading rates, the SPAD value (a measure of leaf cellular chlorophyll content) of the two varieties decreased significantly at the seedling stage compared with CK treatment. No significant change in the SPAD value occurred at the seedling/budding stage or the budding/early-flowering stage. However, the SPAD value increased marginally after shading at the initial flowering stage. Under the 50% shading regime, the SPAD values of both varieties followed the same trend as the 20% regime. The range of changes at different growth stages remained similar. The only exception was that shading at the beginning of flowering increased SPAD value. Shading had little effect on leaf stomatal conductance (g_s) at each developmental stage. There was no significant difference between all treatments and the control, except that the g_svalue of Jizhangshu 8 decreased significantly (43.9%) compared with the control under 50% shading at the beginning of flowering. After the shading treatment, the intercellular CO₂ concentration (C_i) of leaves showed an upward trend. 50% shading at the seedling and seedling/budding stages could significantly increase C_i, but not at other stages. The net photosynthetic rate (P_n) of the four periods were all decreased after 15 d of shading. The P_n reduction of the two varieties, 50% shading, was greater than 20% shading. The decline range of P_n of Jizhangshu 12 was less than that of Jizhangshu 8 at all stages, except for that at the seedling stage. The yield of shading treatments decreased in all four stages, with the decrease rate of 50% shading treatment being greater than that of the 20% shading treatment. ‘Jizhangshu 12'was not tolerant to low light at the seedling stage but performed better than ‘Jizhangshu 8' at other stages. The comprehensive analysis of two test varieties implied that varieties with strong tolerance to low light experienced a smaller boost in intercellular CO₂ concentration and a smaller drop in net photosynthetic rate, stomatal conductance, and yield post-shading.