施肥对干旱胁迫下幼龄期小粒咖啡光合特性及生长的影响

Effects of fertilization on photosynthetic characteristics and growth of Coffea arabica L. at juvenile stage under drought stress

  • 摘要: 为明确氮、磷肥对幼龄期小粒咖啡抗旱性的影响, 采用盆栽试验, 研究了干旱胁迫下3种施氮水平N0 (0 g·株-1)、N1 (2.5 g·株-1)、N2 (7.5 g·株-1)和3种施磷水平P0 (0 g·株-1)、P1 (2.5 g·株-1)、P2 (7.5 g·株-1)的完全处理组合对幼龄期小粒咖啡光合及生长的影响。结果表明: 干旱胁迫下小粒咖啡的叶片相对含水量(LRWC)、最大净光合速率、气孔导度、蒸腾速率、叶绿素含量、比叶面积及生物量均较正常供水时低。干旱胁迫时, 施氮、磷肥均能减缓咖啡LRWC的下降速度, 其中中氮(N1)和磷肥(P1、P2)单施及其配施处理下的LRWC均在72%以上, 显著大于N0P0处理的LRWC。施氮、磷肥有利于改善干旱胁迫下咖啡的光合特性, 其中N0P1、N0P2和N1P2处理的最大净光合速率和水分利用效率显著大于其他处理, 分别是N0P0处理的2.09倍、2.09倍、2.40倍和1.37倍、1.46倍、1.58倍。施氮、磷肥皆可增加叶绿素含量, 还能缓解干旱下叶绿素的降解速度, 且氮磷配施的效应优于氮磷单施。施氮、磷肥有利于小粒咖啡各器官生物量的积累, 而干旱胁迫能促进光合产物向地下部的分配, 各处理的根重比(RMF)和根冠比(R/S)都大于正常供水时的对应值, 其中N0P1和N0P2处理的RMF和R/S最大, 其次是N1P2处理, 且N1P2处理的根干重大于正常供水时的对应值。因此得出, 氮肥和磷肥在改善幼龄期小粒咖啡抗旱性方面发挥着重要作用, 而磷肥的效果优于氮肥, 增强小粒咖啡抗旱性的最佳施肥处理为N1P2

     

    Abstract: To understand the enhancing effects of nitrogen (N) and phosphorus (P) on drought resistance of Coffea arabica L. at juvenile stage, a pot experiment was conducted at the Division of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan Province, China. The experiment consisted of eighteen treatments (in 3 × 3 × 2 design) with three N rates N0 (0 g·plant-1), N1 (2.5 g·plant-1) and N2 (7.5 g·plant-1), three P rates P0 (0 g·plant-1), P1 (2.5 g·plant-1) and P2 (7.5 g·plant-1) and two water treatments (normal water supply and drought stress). To learn the effects of different fertilizer and water treatments on various coffee traits, we mainly investigated coffee leaf relative water content (LRWC), photosynthetic characteristics, chlorophyll content, morphology and biomass allocation. The results showed that LRWC, maximum net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), chlorophyll content, specific leaf area (SLA) and biomass allocation under drought stress were lower than those under normal water supply. Both N and P slowed down LRWC depression induced by drought stress. The LRWC of C. arabica under fertilizer treatments (both single applications of N1, P1 and P2 and combined applications of N1 with P1 or P2) exceeded 72%, and was significantly higher than that of non-fertilizer treatment (N0P0). Both N and P enhanced photosynthetic characteristics of C. arabica. The maximum Pn and water use efficiency (WUE) of fertilizer treatments (N0P1, N0P2 and N1P2) were significantly higher than those of other treatments. Pn of N0P1, N0P2 and N1P2 fertilizer treatments were 2.09 times, 2.09 times and 2.40 times that of N0P0 (non-fertilizer treatment), while the corresponding WUEs were 1.37 times, 1.46 times and 1.58 times that of N0P0. Compared with N0P0, both gs and Tr of fertilizer treatments increased obviously, but with no significant difference among treatments. N and P increased chlorophyll content of coffee leaves and eased chlorophyll degradation rate caused by drought stress. Moreover, combined application of N and P performed better than single application of N or P. The morphology and biomass allocation of C. arabica were obviously influenced by both N and P. And drought stress promoted the distribution of photosynthetic products to underground system, increasing root mass fraction (RMF) and root-to-shoot ratio (R/S), all fertilizer treatments had higher RMF and R/S under drought stress than under normal water supply. N0P1 and N0P2 had the largest RMF and R/S, followed by N1P2 treatment, and root dry weight of N1P2 under drought stress was bigger than under normal water supply. The findings demonstrated that both N and P fertilization were critical for improving drought-resistance of C. arabica at juvenile stage, and N1P2 was the optimum treatment for C. arabica.

     

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