Mucilage inhibits germination of desert ephemeral Nepeta micrantha seed under moderate osmotic stress and promotes recovery after release of this stress

Abstract

Mucilage is considered to play an important role in the survival of seeds in harsh desert environments. Nepeta micrantha is an ephemeral plant of the Gurbantungut Desert, China. The outer surface of N. micrantha nutlets contains a layer of mucilage. We hypothesised that mucilage improves germination during and after osmotic stress. Germination of both intact and demucilaged nutlets under different polyethylene glycol (PEG)-simulated drought stress was tested at the optimal light and temperature conditions. Germination of intact and demucilaged nutlets decreased with an increase in PEG concentration. However, there were no significant differences in germination between intact and demucilaged nutlets at the same PEG concentration, except at 15% PEG. Recovery percentage and final germination of intact nutlets were considerably higher than that of demucilaged nutlets after treatment with 15% PEG. These findings demonstrate that mucilage contributes significantly to drought tolerance ofN. micrantha nutlets by decreasing germination under moderate osmotic stress and aiding germination after the release of this stress.