Plasticity and co‐variation of root traits govern differential phosphorus acquisition among 20 wheat genotypes

Abstract

Trait plasticity (variation of a trait under environmental variability or gradients) and trait integration are both crucial for plant adaption to environmental change. Variations in different suite of root traits such as biomass allocation, morphology and physiology underlie diverse phosphorus (P) acquisition strategies among plants. Yet, how the intraspecific plasticity and integration of root traits influence plant adaptation to different P supply remains obscure. To characterize diverse adaptive strategies in relation to plant P acquisition, eight root traits were assessed in 20 wheat Triticum aestivum genotypes grown in a culture room with low and high P supply. High P supply increased shoot P accumulation and biomass of all wheat genotypes. The shoot P accumulation in genotypes with high P sensitivity (PS: calculated as shoot P content at low P/shoot P content at high P supply) was higher with high P supply and lower with low P supply compared with that in the genotypes with low PS. The high‐PS genotypes exhibited larger variation in root length, root/shoot ratio and rhizosphere pH across P supplies than the low‐PS genotypes, suggesting an integrated response at the whole‐plant level. At low P supply, the high‐PS genotypes had greater root length and specific root length, but lower acid phosphatase activity than the low‐PS genotypes, which suggests contrasting P‐acquisition strategies across the genotypes. Strong co‐variation of root traits occurred across low‐PS genotypes regardless of P supply; conversely, the high‐PS genotypes only exhibited strong trait integration at low P supply, whereas high P supply sharply reduced root trait co‐variation. Our findings suggest that P stress may strengthen root trait integration in wheat plants, and that both plasticity and integration of root traits drive plant adaptive strategies and tolerance to P‐deficiency stress.