Investigating and modeling the combined effects of pH and osmotic pressure on seed germination for use in phytoactivity and allelopathic research

Phytoactivity and allelopathic studies are heavily dependent on germination bioassays of water solutions of allelochemical(s), which necessarily imply that pH and osmotic pressure vary among treatments and between treatments and controls and are therefore a confounding factor in the assessment of seed germination responses to allelochemical(s). When the contribution of pH and osmotic pressure to seed germination responses is considered in experimental designs their effects are almost without exceptions examined separately being assumed, without any evidences, that pH and osmotic pressure act independently on seed germination responses. The objectives of this work were to examine experimentally such assumption using wheat, lettuce, and subterranean clover cultivars to evaluate and model the combined effects on germination of pH and osmotic pressure in the range between 3.0–6.0 and 0–100 mOsmol kg⁻¹, respectively. Empirical equations are fitted, discussed, and the need to consider the simultaneous effects of pH and osmotic pressure firmly established. Finally, the use of the equations fitted and its impact on conclusions is exemplified in a dose-response bioassay of water extracts of <i>Cistus ladanifer</i> on seed germination using subterranean clover as target species where hormesis was found before allelochemical effects were corrected for pH and osmotic pressure values of control and extracts.

植物活性与化感作用研究高度依赖于化感物质水溶液的发芽生物测定，而此类测定必然导致各处理组间、处理组与对照组间的pH与渗透压存在差异，进而成为评估化感物质对种子萌发响应时的混杂因素。若在实验设计中纳入pH与渗透压对种子萌发响应的影响，现有研究几乎无一例外均单独考察二者的效应，且在无任何证据支撑的前提下，默认pH与渗透压对种子萌发响应的作用相互独立。本研究的目标为：以小麦、生菜及地下三叶草品种为材料，通过实验验证上述假设，分别在pH范围3.0~6.0、渗透压范围0~100毫渗摩尔·千克⁻¹的条件下，评估并建模pH与渗透压对种子萌发的联合效应。本研究拟合了经验方程并展开讨论，同时明确了在相关研究中必须同时考虑pH与渗透压的联合效应。最后，本研究以地下三叶草为靶标物种，开展赖百当岩蔷薇（*Cistus ladanifer*）水提物对种子萌发的剂量-反应生物测定，示例了拟合方程的应用及其对研究结论的影响：在未对对照组与提取物的pH及渗透压进行校正前，该实验中被检出了毒物兴奋效应。