水肥耦合对巨能草生长和光合色素的影响

摘要

采用盆栽控制实验的方式，利用控水、控肥的实验方法，设计了干旱（25％ FC）、对照（75％ FC）和水淹（100％FC）3个水分梯度以及低、中、高3个养分水平的完全随机组合实验，研究了不同水肥耦合条件对巨能草生长与光合色素的影响。结果表明，巨能草的地上生物量、地下生物量、生物总量和根冠比都受到了水肥交互作用的显著影响。在正常水分条件下，高肥处理下的分蘖数、株高、地下生物量、地上生物量和生物总量都是最大的，是9种水肥配比中巨能草生物量积累最佳的水肥配比。可见，良好的水肥条件是巨能草获得高产的前提。水淹和干旱都不利于植株的分蘖和高生长，但干旱条件下可通过施肥提高植株的分蘖能力。水淹环境下，不宜施用过多肥料，中等施肥量最有利于巨能草地下生物量的积累，其根冠比显著增大，有利于植物根系适应水淹条件下的缺氧环境。与水淹条件相比，干旱条件更不利于巨能草地上生物量的积累，为了适应干旱环境，巨能草会把更多的同化物质分配给地下部分，进而增大根冠比，从而表现出较高的生理可塑性以适应极端的干旱环境。有趣的是，水分胁迫下的光合色素含量显著高于正常水分，且随着施肥量的增加，光合色素的含量都有所增加，干旱处理下的增加尤为显著。由此可见，在水分胁迫环境下，巨能草会通过其各种形态和生理适应机制来适应环境，表现出一定的耐涝性和抗旱性，且施肥能够在一定程度上降低水分胁迫对植物生长的影响。%A pot experiment was conducted to detect the interaction effect of water and fertilizer on growth and photosynthetic pigments of Puelia sinense .The experiment was a completely randomized design with 9 factori-al combinations of 3 levels of water [drought,25% field capacity (FC);control,75% FC;flooding,100%FC)]and fertilizer (low,moderate,high levels of fertilizer).Above-ground biomass,below-ground biomass, total biomass,and root:shoot ratio were significantly affected by the interaction of water and fertilizer.For the control water treatment,a high level of fertilization led to increased tiller number and plant height,and greater below-ground,above-ground,and total plant biomass.This combination was the best among the 9 combinations.These results indicate that normal supply of water and high nutrient supply are the optimal con-ditions to achieve a high yield for this species.Both flooding and drought were detrimental to tillering and growth.However,under water deficit where a tillering reduction was observed,tillering capacity could be im-proved through fertilization.Under flooding,high fertilization was not beneficial and a moderate amount of fer-tilizer was sufficient for optimal accumulation of below-ground biomass.Plants in these conditions had a higher root to shoot ratio,possibly a plant response to hypoxic conditions.Compared to flooding,drought was more detrimental to the accumulation of above-ground biomass.In order to adapt to drought,P .sinense allocated more assimilate to the belowground organs.The increased root:shoot ratio was presumably advantageous for plant water capture and so to adaptation to drought.Interestingly,under water deficit stress,concentrations of photosynthetic pigments were significantly higher than those under control conditions.With increase in fertili-zation,contents of photosynthetic pigments also increased,especially when exposed to drought at the same time.These results elucidated some morphological and physiological adaptive mechanisms of this species when responding to water-deficit.Increased fertilization could mitigate the detrimental effects of water deficit stress on plant growth to some degree.