The role of mucilage in improving germination and early growth of plants under drought stress (Case study: Plantago ovata and Plantago major)

Seed germination as the most important plant development stages can be frequently affected by environmental stress including drought and salinity. The seeds and/or fruits of many species in desert habitats have an external mucilage layer that can be increased water holding capacity of seeds under water stress condition. To evaluate the role of mucilage in enhancing of drought tolerance of Plantago ovata Forsk. and Plantago major L. in seed germination and early growth stages، a completely randomized experiment was conducted in a factorial arrangement with four replications. Plant species (P. ovata، P. major)، drought stress levels (0، -5، -9، - 14. 5، -21 MPa) and seed type (with mucilage، and without mucilage) were considered as first، second and third factors، respectively. Different variables including germination percentage، rate of germination، stem as well as root length were measured. Results indicate that with increasing drought stress، germination and seedling growth of two plant species were significantly decreased. Seeds with mucilage were less affected by drought stress compared to the seeds without mucilage. Germination and early growth of the two plant species differ in their sensitivity to drought stress and P. major was more affected by drought stress. Overall، results indicate that mucilage can improveseed germination of both plant species under drought stress condition. However، the ability of mucilage in improving seed germination depends on type of plant species and amount of seeds mucilage.