Effect of Brassinosteroids on Germination and Seedling Growth of Radish (<i>Raphanus sativus</i>L.) under PEG-6000 Induced Water Stress

Effect of 24-epibrassinolide and 28-homobrassinolide on the germination and seedling growth of radish (Raphanus sativus) subjected to water stress being imposed by 15% (w/v) polyethylene glycol (equivalent to -2.95 bars of osmotic pressure) was studied. Brassinosteroids supplementation reduced the inhibitory effect of water stress on seed germination and seedling growth. The growth stimulation in radish seedlings by brassinosteroids under desiccation stress was associated with elevated levels of nucleic acids and soluble proteins and lowered activities of RNase. The mitigation of osmotic stress imposed by PEG was associated with increased scavenging of reactive oxygen species as reflected in elevated activities of superoxide dismutase, catalase and ascorbate peroxidase. Brassinosteroids also enhanced the accumulation of the osmolyte free proline in radish seedlings challenged with drought stress. The two brassinosteroids also maintained membrane integrity under water deficiency conditions as indicated by lowered lipid peroxidation reflecting in reduced MDA content. The results of present study demonstrate the protective role of brassinosteroids against PEG imposed water stress in radish seedlings.

The Influence of Induced Drought Stress on Germination of Cenchrus ciliaris L.and Cenchrus setigerus Vahl.:Implications for Rangeland Restoration in the Arid Desert Environment of Kuwait

Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity.Imple­mentation of restoration projects in arid desert environments is largely dependent on water availability and soil mois­ture condition.This study investigated the influence of induced drought stress by using polyethylene glycol(PEG-6000)solution on germination viz.Cenchrus ciliaris and Cenchrus setigerus as the important rangeland species.The water stress potential treatments were 0(control),-0.5 MPa,-1.0 MPa,-1.5 MPa,and-2.0 MPa.The extent of seed germi­nation was severely affected by decreased water stress potential.As drought increased,the percentage of germination decreased in both Cenchrus’species.The water deficit at-0.5 MPa showed a significant(P<0.001)reduction in the final germination percentage in the case of C.setigerus and C.ciliaris by 65%and 42.5%,respectively.At-1.0 MPa to-1.5 MPa,changes in intermediate germination were observed in C.ciliaris(from 35%to 17.5%,respectively)and C.setigerus(from 22.5%to 11.25%respectively).Higher levels of water stress(-2.0 MPa)prevented the survival of both species.Understanding the germination strategies of native desert plant species associated with drought stress and identifying favorable conditions during the germination process can be useful for restoration practices and rangeland management actions to improve desert ecosystems and maintain biodiversity.