Differential responses of accessions of native Australian Nicotiana species to water stress

Abstract

Thirty-two accessions of four Nicotiana species (Nicotiana benthamiana Domin, Nicotiana occidentalis H.-M.Wheeler, Nicotiana simulans N. Burb. and Nicotiana umbratica N.T.Burb.) collected from wild plants in northern Australia were assessed for responses to water stress. Under moderate water stress conditions, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, root : shoot ratio, and relative water content of leaves were significantly affected. However, the degree to which the accessions were affected varied considerably. Some accessions of N. simulans, N. benthamiana and N. occidentalis were significantly more affected by water stress than others. There was significant variation between accessions in leaf and shoot tip wilting times. Initial symptom expression (leaf wilting) was significantly delayed in three accessions of N. benthamiana, and in one accession of N. umbratica. The least water stress tolerant lines, two accessions each of N. benthamiana, N. occidentalis and N. simulans, exhibited advanced symptoms of water stress (shoot tip wilting) within 14–17 days of cessation of watering. This stage was significantly delayed in three accessions of N. benthamiana and two accessions N. occidentalis and one accession of each of N. simulans and N. umbratica, which showed tip wilting only after 21–24 days. There were variations among the accessions of same Nicotiana species on their tolerance to water stress. Plant responses to water stress could not be predicted from their plant biomass and leaf relative water content under well-watered conditions. Leaf chlorophyll content was variable under water stress, but did not correlate with water stress tolerance.