Table_2_Tomato Rootstocks Mediate Plant-Water Relations and Leaf Nutrient Profiles of a Common Scion Under Suboptimal Soil Temperatures.DOCX

Environments with short growing seasons and variable climates can have soil temperatures that are suboptimal for chilling-sensitive crops. These conditions can adversely affect root growth and physiological performance thus impairing water and nutrient uptake. Four greenhouse trials and a field study were conducted to investigate if rootstocks can enhance tomato performance under suboptimal soil temperatures (SST). In a controlled greenhouse environment, we exposed four commercial rootstocks (Estamino, Maxifort, RST-04-106-T, and Supernatural) grafted with a common scion (cv. BHN-589) to optimal (mean: 24°C) and SST (mean: 13.5°C) and compared their performance with the non-grafted BHN-589 cultivar. Several root and shoot physiological traits were evaluated: root hydraulic conductivity and conductance, root anatomy, leaf gas exchange, leaf δ13C, shoot C and N, and biomass. Under field conditions, the same five phenotypes were evaluated for canopy growth, normalized difference vegetation index (NDVI), leaf nutrients, biomass, and yield. Under SST, root hydraulic conductivity (Lp) and conductance (KR), stomatal conductance (gs), and plant biomass decreased. Hydrostatic Lp decreased more than osmotic Lp (Lp∗hyd: 39–65%; Lp∗os: 14–40%) and some of the reduced conductivity was explained by the increased cortex area of primary roots observed under SST (67–140%). Under optimal soil temperatures, all rootstocks conferred higher gs than the non-grafted cultivar, but only two rootstocks maintained higher gs under SST. All phenotypes showed greater reductions in shoot biomass than root biomass resulting in greater (∼20%) root-to-shoot ratios. In the field, most grafted phenotypes increased early canopy cover, NDVI, shoot biomass, and fruit yield. Greenhouse results showed that Lp∗os may be less affected by SST than Lp∗hyd and that reductions in Lp may be offset by enhanced root-to-shoot ratios. We show that some commercial rootstocks possess traits that maintained better rates of stomatal conductance and shoot N content, which can contribute toward better plant establishment and improved performance under SST.

生长季短促且气候波动剧烈的生境中，土壤温度往往无法满足低温敏感作物的最佳生长需求。此类环境条件会对作物根系生长与生理活性产生不利影响，进而损害其水分与养分吸收能力。本研究开展了4组温室试验与1项田间试验，旨在探究砧木能否在亚适土壤温度（suboptimal soil temperatures, SST）下提升番茄的生长表现。在可控温室环境中，本研究将4种商业砧木（Estamino、Maxifort、RST-04-106-T与Supernatural）与统一接穗（品种BHN-589）进行嫁接，分别置于适宜土壤温度（平均24℃）与亚适土壤温度（平均13.5℃）环境下处理，并以未嫁接的BHN-589品种作为对照进行性能对比。本研究测定了多项根系与地上部的生理性状：根系导水率与导度、根系解剖结构、叶片气体交换参数、叶片δ¹³C、地上部碳氮含量以及生物量。在田间条件下，针对上述5种表型，本研究测定了冠层生长情况、归一化植被指数（normalized difference vegetation index, NDVI）、叶片养分含量、生物量与果实产量。在亚适土壤温度条件下，作物根系导水率（Lp）、根系导度（KR）、气孔导度（gs）以及植株生物量均出现下降。静水压导水率（Lp*hyd）的下降幅度大于渗透压导水率（Lp*os）（Lp*hyd降幅为39%~65%，Lp*os降幅为14%~40%）；部分导水率的降低可归因于亚适土壤温度下初生根皮层面积的增加（增幅67%~140%）。在适宜土壤温度条件下，所有砧木处理组的气孔导度均高于未嫁接对照组，但在亚适土壤温度条件下仅2种砧木仍能维持较高的气孔导度。所有表型的地上部生物量降幅均大于根系生物量，最终导致根冠比提升约20%。田间试验结果显示，多数嫁接处理组的早期冠层覆盖度、归一化植被指数、地上部生物量与果实产量均有所提升。温室试验结果表明，相较于静水压导水率，渗透压导水率受亚适土壤温度的影响更小；而根冠比的提升可部分抵消根系导水率的下降幅度。本研究证实，部分商业砧木具备维持较高气孔导度与地上部氮含量的特性，这有助于提升植株在亚适土壤温度条件下的定植成活率与生长表现。