Comparative Effects of Drought and Salt Stress on Germination and Seedling Growth of <i>Pennisetum divisum</i> (Gmel.) Henr.

Abstract

Problem statement: Water stress due to drought and salinity is probably the most significant abiotic factor limiting plant and also crop growth and development. Salinity and drought stresses are physiologically related, because both induce osmotic stress and most of the metabolic responses of the affected plants are similar to some extent. Water deficit affects the germination of seed and the growth of seedlings negatively. Temperature is an exceedingly important factor in seed germination. It directly affects whether a plant can sprout and, if so, how long it will take to emerge from the ground. Approach: The objective of this investigation was to determine the effect of four alternating temperature regime, drought and salt stress on germination characteristics of Pennisetum divisum. Seeds were germinated at four alternating temperatures (10/20, 15/25, 20/35 and 25/40°C at 12 h light). Seeds were also germinated with the iso-osmotic concentrations of sodium chloride (NaCl) or in polyethylene glycol PEG8000 (0, -0.2, -0.4, -0.6 and -0.8 MPa) for 14 days. Concentrations were applied to determine their effects on seed germination and seedling growth under laboratory conditions. The effects of different osmotic concentrations of NaCl and PEG were compared to distilled water (control). Results: Optimum germination was attained at 15/25°C which corresponds to temperatures prevailing during spring time. The highest values of germination parameters were obtained with no osmotic potential (0 MPa) under 15/25°C. The final germination percentage and rate of germination in the Pennisetum divisum treated seeds were decreased with the increase of the osmotic potential. At treatment by PEG, the germination was severely decreased at -0.6 MPa. While, no germination occurred at-0.8 MPa by NaCl. The results of the effects of the different osmotic potential of NaCl and PEG on the Radicle Length (RL) and the Hypocotyl Length (HL) mm of the tested P. divisum seeds were retarded when compared to the control. Conclusion: Results indicated germination sensitive to both the stresses. However, seedling growth was more sensitive to NaCl than was germination. However, seedling growth was more sensitive to NaCl than was germination responses to water stress induced by PEG and NaCl. Results also indicated that seed germination of P. divisum is less sensitive to osmotic potential indicating that the seeds of the species are efficient in osmotically adjusting to soluble salts. This suggests the possibility of revegtating moderately salt affected soils.

Oligoglucans as Elicitors of an Enzymatic Antioxidant System in Zucchini Squash (<i>Cucurbita pepo</i> L.) Seedlings at Low Temperature

“…Indeed, H 2 O 2 levels in coldstressed zucchini cotyledons increased significantly after 7 d. This result reveals a typical response of low temperature treatments in stressed plants, such as cucumber, maize (Dat et al, 2000) and Gramineae grasses (Al-Taisan, 2010). Zucchini cotyledons showed a linear correlation between H 2 O 2 accumulation and membrane damage measured as IL, contrary to the same parameters evaluated in barley plants infected with powdery mildew (Harrach et al, 2008).…”

“…Generally, if plants are in non-stress conditions, ROS production and scavenging processes are in equilibrium; however, this condition can be easily perturbed by extreme temperatures and several abiotic and biotic factors (Del Río et al, 2006). For example, ROS accumulation begins in chloroplasts and mitochondria of plants, such as wheat, cucumber, corn, Arabidopsis thaliana and rice, due to low temperature condition (Dat et al, 2000;Al-Taisan, 2010). To decrease the damage of ROS in biomolecular targets (proteins, nucleic acids and lipids), plants employ a complex antioxidant system that helps them restore cellular redox homeostasis.…”

Effect of ecological factors on germination of horse purslane (Trianthema portulacastrum)

“…Similar results were observed by Nandula et al (2009) for LoIium multiflorim, whose germination was reduced from 79 to 8% when drought stress increased from 0 to -0.8 MPa. Taisan (2010) reported that drought stress decreased and delayed germination of Pennisetum divisum and germination was only 10% at drought stress of -0.8 MPa. The significant reduction in germination of T. portulacastrum, even at moderate drought stress levels, is in contradiction to the results of Singh (2009), who reported that moderate stress intensities only delayed germination, whereas the highest concentration of PEG reduced final germination percentages of Sorghum halepense.…”

“…Salinity causes considerable decline in germination percentage and seedling growth by specific ion toxicity and osmotic effect (Taisan, 2010). The level of drought and salinity at which germination is reduced varies with species, genotype, environmental conditions, osmotic potential and specific ions (Ungar, 1991).…”

Evaluation of <i>Hevea brasiliensis</i> (Latex Timber Clone: RRIM 2001 and RRIM 3001) in Relation to Different Water Stress

“…Plant water status is also affected by reducing of water availability in plant. More than that, water stress influences plant growth at various levels, including cell community (Al-Taisan, 2010;Blumwald et al, 2004;Colom and Vazzana, 2001). The quantity and quality of plant growth depend on cell division enlargement and differentiation and all of these events are affected by water stress (Cabuslay et al, 2002;Correia et al, 2001).…”