Effects of irrigation with amended dilutions of seawater on germination, growth and ionic distribution in Pennisetum divisum (GMEL.) HENR - An arid psammophytic perennial graminoid

Germination, growth and ionic distribution in Pennisetum divisum (Gmel.) Henr. were investigated using 10-30% amended sea water (ECiw: 4.5-14.0 dS.m-1) for irrigation. Fifty percent reduction in germination (in petriplates) corresponded with ECiw: 10.44 dS.m-1 and threshold ECiw corresponding with 50% reduction in growth (in drum pot culture) was around 10.13 plus minus 1.01 dS.m-1 (ranging from 8.57 to 12.25 dS.m-1 when assessed in terms of root, residual shoot, harvested shoot and total plant biomass). The plant showed decline in regeneration after bi-monthly clipping around the year. The growth was extremely reduced during winter season (dormancy period). The cumulative forage biomass harvested per annum under 30 %, amended seawater (14.0 dS.m-1) was 1267.67 plus minus 234.67 g.drum-1 (FW). It was 5467.0 plus minus 261.4 g.drum-1 (FW) in control (1.2 dS m-1) reduction being c. 76.8%. The reduction in forage production in 10 and 20% seawater was c.48.3 and c.61.3%, respectively. The plant showed dowering throughout the year. The plant irrigated with saline water showed decrease in chlorophyll and water content. Sugar contents remained statistically indifferent in leaves up to 20% seawater irrigation but increased in 30% seawater. Although proline level increased considerably, protein concentration remained quite unaffected. Sodium increased in the roots as well as shoots. Potassium concentration, which increased in roots of plants, irrigated kith 10% seawater declined in 20 and 30 % seawater. It didn't vary in leaves up till 20% seawater. In leaves calcium declined at higher salinity. Mg concentration which increased in leaves (63.5%) of plants irrigated with low salinity declined in higher salinity but didn't vary significantly from that in the control plants K/Na ratio was much higher in shoot and Ca/ Mg ratio was relatively higher in roots. Mg concentration was relatively higher in shoot than root of the treated plants