The Growth and Physiological Responses of Gleditsia Sinensis Lam. Seedlings with Different Phosphorus Efficiencies to Low Phosphorus Stress

In order to elucidate the response mechanisms of Gleditsia sinensis Lam. with different phosphorus (P) efficiencies to low P stress, this study set up low P treatment (0.01 mmol·L−1, LP) and normal P treatment (1.00 mmol·L−1, NP). The experimental materials included low P-tolerant G. sinensis families F10 and F13, and low P-sensitive G. sinensis families F21 and F29. This study aimed to investigate the effects of low P stress on the agronomic traits, nutrient content, and physiological indices of G. sinensis seedlings with different P efficiencies. The results showed that the agronomic traits, such as plant height, stem diameter, and so on, of the low P-tolerant family, were significantly higher than those of the low P-sensitive family under low P stress. Low P stress significantly increased the total root length, total root surface area, total root projected area, total root volume, and main root diameter of the tolerant family. The tolerant family exhibited significantly higher net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate compared to the sensitive family. Low P stress significantly increased the activities of protective enzymes, acid phosphatase activity, and malondialdehyde content in the low P-tolerant family. The tolerant family exhibited higher P absorption efficiency and P utilization efficiency compared to the sensitive family. Low P stress significantly increased the P utilization efficiency of the tolerant family. In summary, compared to the sensitive family, the low P-tolerant G. sinensis family has stronger reactive oxygen species scavenging ability and can accumulate more osmotic regulatory substances to maintain cell osmotic potential and better protect cells; this improves P utilization efficiency and nutrient content, thereby alleviating the harm caused by low P stress and maintaining normal growth and metabolism.