Soil fertility and heavy metal pollution (Pb and Cd) alter kin interaction of Sorghum vulgare

Abstract

Plant kin recognition has been confirmed in some plant species, but it remains unclear how kin recognition is related to soil conditions such as fertility and heavy metal stress (Lead or Cadmium). A three-factor experiment based on soil fertility, neighbor’s kinship and heavy metal addition was conducted using Sorghum vulgare as a target plant. Plant morphological traits, physiological traits and plant nutrient use efficiency (NUE) and heavy metal concentrations of lead (Pb) and Cadmium (Cd) were measured to determine plant kin interactions.Significant soil fertility, kinship, heavy metal, and their interactive effects were observed on measured indicators. Kin plants showed higher specific leaf area (SLA), root activity, the NUE of phosphorus (P) and sulphur (S) than strangers in nutrient-poor soil. When in nutrient-rich soil, lower SLA and the NUE of nitrogen (N) and sodium (Na) were observed in kin than strangers. Under Pb stress, decreased stem elongation and the NUE of potassium (K), whereas increased malondialdehyde (MDA) and proline content were observed in kin than strangers in nutrient poor-soil. On contrast, kin plants increased the stem elongation, SLA, root activity, and the NUE of S compared to strangers in nutrient-rich soil; Under Cd stress, kin plants decreased the total biomass, the NUE of P, as well as the content of chlorophyll and proline, while increased the MDA and Cd concentration compared to strangers in nutrient-poor soil. Kin plants increased the SLA, root activity, MDA content and Cd concentration, while decreased the NUE of S compared to strangers in nutrient-rich soil. Under Pb plus Cd stress, compare to strangers, kin plants produced higher biomass and the NUE of P in nutrient-poor soil, whereas exhibited lower stem elongation, less proline, Pb and Cd concentration than strangers in nutrient-rich soil.We conclude that kin recognition of S. vulgare was soil fertility and heavy metal stress depended. Kin benefit occurred below ground in nutrient poor soil, while it occurred above ground in nutrient rich soil. Pb stress alone made co-occurrence of kin recognition and competition, while Cd stress alone supported kin competition. By comparison, the Pb plus Cd stress supported kin recognition of S. vulgare. Plant NUE for specific elements, combined with morphological and physiological performance, can be used as sensitive response indicators for kin recognition under complicated soil conditions.