Exogenous IAA enhances low potassium tolerance of sweetpotato by regulating root response strategy

ABSTRACT

Plant roots are sensitive to potassium (K⁺) deficiency signals. Therefore, regulating root growth by exogenous methods is a vital strategy to improve low K⁺ tolerance of sweetpotato. We studied the effects of exogenous indole-3-acetic acid (IAA) on growth, K⁺ absorption, and root characteristics in sweetpotato exposed to low K⁺ treatment (LK). LK significantly inhibited dry mass, K⁺ concentration and accumulation, as well as the root elongation (length) and branching (forks and crossings) in sweetpotato seedlings. However, exogenous IAA increased the length, ratio, and density of lateral roots and promoted absorption and accumulation of K⁺, which effectively alleviated the inhibitory effect of low K⁺. Exogenous IAA also increased the expression levels of auxin synthesis (IbYUC6 and IbTAR2) and transport (IbPIN1, IbPIN3, and IbPIN8) genes in leaves and roots, which promoted the increase of endogenous IAA content. Furthermore, exogenous IAA was more effective on low-K-tolerant variety (XS32) than low-K-sensitive variety (NZ1) under LK stress, depending on their different IAA synthesis and transport strategies. These results indicated that exogenous IAA enhanced root responsiveness of sweetpotato to low K⁺ stress by modulating auxin biosynthesis and transport, thereby improving the tolerance of sweetpotato to low K⁺ stress.

KEYWORDS:

• Exogenous methods
• expression analysis
• lateral root
• nutrition stress
• sweetpotato

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was financially supported by the National Natural Science Foundation of China (32001482), and the China Agriculture Research System of MOR and MARA (CARS-10, sweetpotato).