Responses of plant growth, root morphology, chlorophyll and indoleacetic acid to phosphorus stress in trifoliate orange

Abstract

Background and Objective: In citriculture, citrus trees are often exposed to low soil phosphorus (P) levels, resulting in low fruit production. The present study aimed to analyze the changes in plant growth, biomass production, root morphology, chlorophyll and root indoleacetic acid (IAA) of trifoliate orange (Poncirus trifoliata L Raf.) in response to different substrate P stresses. Methodology: Five-leaf-old trifoliate orange seedlings were grown in plastic pots supplied with sands, accompanied with the Hoagland solution with no-P (0 mM P), low-P (0.1 mM P), adequate-P (1 mM P) and high-P (10 mM P) treatments for 8 weeks. Results: No-P, low-P and high-P treatments significantly decreased plant height, stem diameter, leaf number and shoot and root biomass as compared with adequate-P. An increased trend in root morphological traits (total length, surface area, projected area, volume, taproot length and No. of 1st and 2nd order lateral roots) was from 0-1 mM P levels and a decreased trend was from 1-10 mM P levels. Compared with adequate-P treatment, no-P, low-P and high-P treatments significantly decreased chlorophyll a and carotenoid level. In addition, low-P and high-P treatments significantly increased root IAA concentration relative to adequate-P. Conclusion: The results of this study suggested that low-P and high-P considerably inhibited plant growth and root development, which may be closely related with chlorophyll changes but not with root IAA levels.