Investigating the Water Availability Hypothesis of Pot Binding: Small Pots and Infrequent Irrigation Confound the Effects of Drought Stress in Potato (Solanum tuberosum L.) Data

To maximise the throughput of novel, high-throughput phenotyping platforms, many researchers have utilised smaller pot sizes to increase the number of biological replicates that can be grown in spatially limited controlled environments. This may confound plant development through a process known as “pot binding”, particularly in larger species including potato (Solanum tuberosum), and under water-restricted conditions. We aimed to investigate the water availability hypothesis of pot binding, which predicts that small pots have insufficient water holding capacities to prevent drought stress between irrigation periods, in potato. Two cultivars of potato were grown in small (5 L) and large (20 L) pots under glasshouse conditions and were subjected to three irrigation frequencies: every other day, daily, and twice daily. Plants were phenotyped with two Phenospex PlantEye F500s and canopy and tuber fresh mass and dry matter were measured. Increasing irrigation frequency from every other day to daily was associated with a significant increase in fresh tuber yield, but only in large pots. This suggests a similar level of drought stress occurred between these treatments in the small pots, supporting the water availability hypothesis of pot binding. Further increasing irrigation frequency to twice daily was still not sufficient to increase yields in small pots but caused an insignificant increase in yield in the larger pots, suggesting some pot binding may be occurring in large pots under daily irrigation. Canopy temperatures were significantly higher under each irrigation frequency in the small pots compared to large pots, which strongly supports the water availability hypothesis as higher canopy temperatures are a reliable indicator of drought stress in potato. Digital phenotyping was found to be less accurate for larger plants, probably due to a higher degree of self-shading. The research demonstrates the need to define the optimum pot size and irrigation protocols required to completely prevent pot binding and ensure drought treatments are not inadvertently applied to control plants.为最大化新型高通量表型平台的运行通量，诸多研究者采用更小规格的栽培盆钵，以在空间受限的可控培养环境中培育更多生物学重复样本。但该做法可能通过一种被称为“盆钵束缚效应（pot binding）”的过程干扰植物生长发育，对于包括马铃薯（Solanum tuberosum）在内的大型物种，以及处于水分限制条件下的植株而言，该效应尤为显著。本研究旨在验证盆钵束缚效应的水分可利用性假说——该假说预测小型栽培盆钵的持水量不足，无法在两次灌溉间隔间避免干旱胁迫，研究对象为马铃薯。本实验将两个马铃薯栽培品种分别种植于规格为5 L的小型盆钵与20 L的大型盆钵中，于温室栽培环境下设置三种灌溉梯度：每隔一日灌溉一次、每日灌溉一次、每日灌溉两次。采用两台Phenospex PlantEye F500表型成像设备对植株进行表型鉴定，并测定植株冠层与块茎的鲜重及干物质含量。将灌溉频率从每隔一日提升至每日一次，仅在大型盆钵组中观测到块茎鲜产的显著提升。该结果表明小型盆钵的两组灌溉处理间存在相近程度的干旱胁迫，支持了盆钵束缚效应的水分可利用性假说。进一步将灌溉频率提升至每日两次，仍未能提升小型盆钵的块茎产量，但在大型盆钵组中仅带来了统计学上不显著的产量提升，这表明在每日灌溉条件下，大型盆钵仍可能存在一定程度的盆钵束缚效应。相较于大型盆钵组，小型盆钵组在所有灌溉频率下的冠层温度均显著更高，这一结果有力支持了水分可利用性假说——冠层温度升高是马铃薯植株干旱胁迫的可靠指示指标。研究同时发现，数字表型鉴定技术对大型植株的检测准确性更低，这可能源于植株自身遮阴程度更高。本研究表明，需明确最优的栽培盆钵规格与灌溉方案，以完全避免盆钵束缚效应，并确保干旱处理不会被意外施加于对照植株。