The combined effect of root morphological and resistance traits alleviated the growth limitations of Pinus massoniana seedlings under low phosphorus conditions

Understanding the adaptive strategies of plants to phosphorus (P) deficiency, particularly the plasticity of structural and physiological responses, is crucial for predicting plant growth. Our study aimed to investigate the growth, root morphological and resistance trait responses of Pinus massoniana seedlings under a fact-based low-P range.

A P manipulation experiment (0–9.299 mg·kg⁻¹) was carried out to measure biomass, root morphological and resistance traits of P. massoniana seedlings.

The root to shoot biomass ratio changed, however, the belowground biomass did not change in response to decreased P content of the growing substrate. Seedlings extended fine roots (0–2 mm in length) thus increased root surface area to enhance P uptake. The length of coarse root (> 5 mm) and root average diameter increased with P addition. A strong response was found in root resistance traits, which also exhibited higher plasticity and made greater contributions to growth. Antioxidant enzyme activities, malondialdehyde content, acid phosphatase activity, and organic acid content all decreased with P addition, but root vigor showed a more sensitive response, making it a potentially informative indicator for changes in P conditions.

Physiological traits related to root resistance were more sensitive and important in plant growth regulation, while root morphological traits showed different adaptative strategies among root classes to regulate biomass and absorptive function. The combined effects of morphological and resistance traits alleviate the limitation of P on plant growth. Our findings will provide insights into the adaptive strategies of plantation growing in subtropical regions under limiting nutrient environment.