基质与灌溉耦合对大叶绣球光合特性和水分利用效率的影响

Effects of substrate-coupled irrigation on Hydrangea macrophylla photosynthetic characteristics and water use efficiency

【目的】研究不同基质类型和灌溉方式对大叶绣球光合特性和水分利用效率的影响,揭示大叶绣球对不同基质与灌溉措施的响应规律,为其科学灌溉和高效栽培提供依据。【方法】在上海辰山植物园大棚内搭建智能灌溉系统,以2年生大叶绣球(品种为花手鞠)为供试材料进行田间盆栽试验。设置3种栽培基质类型:园土(S1)、50%园土+50%园林废弃物(S2)、50%园土+40%园林废弃物+10%生物炭(S3);设两种灌溉方式:充分灌溉(FI)、亏缺灌溉(DI)。测量大叶绣球株高、冠幅和生物量,测定光合特性(气体交换参数、光合-CO_(2)响应曲线和相对叶绿素含量SPAD)、气孔形态特征(气孔大小和气孔密度)、叶水势和碳同位素分辨率(Δ^(13)C),计算植物生长指数和植株水分利用效率,并对指标进行相关性和主成分分析。【结果】基质类型和灌溉方式显著影响了大叶绣球光合特性和水分利用效率(P<0.05)。与FI相比,DI条件下大叶绣球叶片的净光合速率(P_n)、气孔导度(G_(S))、蒸腾速率(T_(r))、初始羧化速率(R_(p))、光呼吸速率(Γ)和相对叶绿素含量(SPAD)均显著降低,但生物炭的添加(S3)显著提高了DI条件下叶片的Pn、Rp、Γ和SPAD值。S1、S2和S3在DI条件下的总耗水量表现为S1>S3>S2,与FI相比,分别节约用水22.9%、65.1%和63.1%。DI条件下,不同基质的植物生长指数和地上生物量均表现为S1<S2<S3,与S1相比,S2、S3的植物生长指数分别显著增加了16.7%、30.1%;地上生物量分别增加了0.5和1.3倍。S2和S3基质使得大叶绣球在低耗水量的同时维持了较高的地上生物量,其中生物炭的添加(S3)使大叶绣球叶片瞬时水分利用效率(WUE_(i))、内在水分利用效率(WUE_n)、气孔密度和叶水势显著提高,而Δ^(13)C显著减低,保持了最高的地上生物量和植株水分利用效率。相关性分析表明Δ^(13)C与WUE_(i)和WUE_n呈极显著的负相关关系,且Δ13C对WUE_n的指示性更优;主成分分析表明R_(p)和WUE_n在光合特性和水分利用效率指标中起主导作用。【结论】生物炭和亏缺灌溉的联合应用缓解了水分限制的负面影响,提高了叶片对CO_(2)的利用能力,在维持大叶绣球生长的同时提高了水分利用效率,是提高大叶绣球水分利用效率的适宜栽培组合。

【Objectives】This study aims to investigate the impact of various substrate types and irrigation methods on the photosynthetic characteristics and water use efficiency (WUE) of Hydrangea macrophylla.It seeks to elucidate the plant’s adaptive mechanisms to different substrate-irrigation combinations,providing insights for scientific irrigation and efficient cultivation.【Methods】A pot experiment was conducted using 2-year-old Hydrangea macrophylla (‘Hanatemari’) and an intelligent irrigation system was built in the greenhouse of Chenshan Botanical Garden in Shanghai.Three substrate types (S1:garden substrate,S2:50%garden substrate+50%garden waste,S3:50%garden substrate+40%garden waste+10%biochar) and two irrigation methods (full irrigation,FI;deficit irrigation,DI) were set up.Plant height,crown width,and biomass of H.macrophylla were measured,and photosynthetic characteristics (gas exchange parameters,photosynthetic-CO_(2) response curves,and relative chlorophyll content),stomatal morphological features (stomatal size and stomatal density),leaf water potential,and carbon isotope discrimination (Δ~(13)C) were determined.Plant growth indices and water use efficiency were calculated,and correlation and principal component analyses were performed on the indicators.【Results】Both substrate type and irrigation method significantly influenced the photosynthetic characteristics and water use efficiency of H.macrophylla (P<0.05).Compared with FI,under DI conditions,the net photosynthetic rate (P_n),stomatal conductance (G_S),transpiration rate (T_r),initial carboxylation rate (R_p),photorespiration rate (Γ),and relative chlorophyll content (SPAD) of H.macrophylla leaves were significantly reduced,but the addition of biochar (S3) significantly increased P_n,R_p,Γ,and SPAD values of leaves under DI conditions.Compared with FI,under DI conditions,the total water consumption of three substrate types showed a pattern of S1>S3>S2,saving water by 22.9%,65.1%,and 63.1%,respectively.Under DI conditions,the plant growth index and above ground biomass of the different substrates showed a pattern of S1<S2<S3,with S2 and S3 significantly increasing the plant growth index by 16.7%and 30.1%,and above ground biomass by 0.5 times and 1.3 times compared with S1,respectively.S2 and S3 substrates maintained a high aboveground biomass while conserving water,and the addition of biochar (S3) significantly increased instantaneous water use efficiency (WUE_i),intrinsic water use efficiency (WUE_n),stomatal density,and leaf water potential,while significantly reducingΔ~(13)C,maintaining the highest aboveground biomass and plant water use efficiency.Correlation analysis showed a highly significant negative correlation betweenΔ~(13)C and both WUE_(i) and WUE_n,withΔ~(13)C being more indicative of WUE_n;principal component analysis showed that R_(p) and WUE_(n) played a dominant role in photosynthetic characteristics and water use efficiency indicators.【Conclusions】The synergistic application of DI and S3 substrate mitigates the adverse effects of water scarcity,improving leaf utilization of CO_(2),sustaining plant growth and augmenting WUE in H.macrophylla.This combination emerges as an effective cultivation strategy for enhancing the plant's water efficiency.