Root Foraging Strategy Improves the Adaptability of Tea Plants (Camellia sinensis L.) to Soil Potassium Heterogeneity

Root foraging enables plants to obtain more soil nutrients in a constantly changing nutrient environment. Little is known about the adaptation mechanism of adventitious roots of plants dominated by asexual reproduction (such as tea plants) to soil potassium heterogeneity. We investigated root foraging strategies for K by two tea plants (low-K tolerant genotype 1511 and low-K intolerant genotype 1601) using a multi-layer split-root system. Root exudates, root architecture and transcriptional responses to K heterogeneity were analyzed by HPLC, WinRHIZO and RNA-seq. With the higher leaf K concentrations and K biological utilization indexes, 1511 acclimated to K heterogeneity better than 1601. For 1511, maximum total root length and fine root length proportion appeared on the K-enriched side; the solubilization of soil K reached the maximum on the low-K side, which was consistent with the amount of organic acids released through root exudation. The cellulose decomposition genes that were abundant on the K-enriched side may have promoted root proliferation for 1511. This did not happen in 1601. The low-K tolerant tea genotype 1511 was better at acclimating to K heterogeneity, which was due to a smart root foraging strategy: more roots (especially fine roots) were developed in the K-enriched side; more organic acids were secreted in the low-K side to activate soil K and the root proliferation in the K-enriched side might be due to cellulose decomposition. The present research provides a practical basis for a better understanding of the adaptation strategies of clonal woody plants to soil nutrient availability.

Automated summary

This study investigated the root foraging strategies of tea plants under soil potassium heterogeneity. It found that the low-K tolerant genotype 1511 showed better acclimation to K heterogeneity than the low-K intolerant genotype 1601. The adaptation of 1511 was attributed to a smart root foraging strategy, including the development of more roots (especially fine roots) in the K-enriched side, secretion of more organic acids in the low-K side to activate soil K, and cellulose decomposition promoting root proliferation. This research provides practical insights into the adaptation strategies of clonal woody plants to soil nutrient availability.