Improving Tolerance of Vachellia farnesiana Plants to Irrigation Water Salinity by Using Bio-Inocula under Sandy Soil Conditions

摘要

This study was conducted at the Experimental Laboratory of the Natural Resources Department, Inst.of African Res. and Studies, Cairo Univ., Giza, Egypt and Experimental Nursery of Ornamental HorticultureDepartment, Faculty of Agric., Cairo Univ., Giza, Egypt during the two successive seasons of 2013/2014 and2014/2015. The aim of this study was to investigate the possibility of improving tolerance of Vachelliafarnesiana plants grown in sandy soil to irrigation water salinity by using bio-inocula. Seedlings of Vachelliafarnesiana were inoculated with mixed spores of arbuscular mycorrhizal fungi (AM) from genera Glomus,Gigaspora and Acaulospora (450 spores/g sterilized peatmoss as a carrier) at the rate of 10g /pot alone, withtwo different Sinorhizobium terangae strains of bacteria (R, 109 CFU/ml) at the rate of 10 ml/ pot, or with mixedspores of arbuscular mycorrhizal fungi (AM) followed by the two Sinorhizobium terangae strains after themycorrhizal symbiosis was established (AM+ R). The plants were irrigated (till 85% of field capacity) every 4days using tap water (control, 300 ppm salinity) or tap water containing a mixture of NaCl and CaCl2 (1:1 w/w)at concentrations of 3000, 6000, 9000 or 12000 ppm. Increasing irrigation water salinity concentrationsignificantly reduced survival percentage, plant height, stem diameter, number of branches/plant, root lengthas well as fresh and dry weights of branches + leaves and roots/plant, total chlorophylls, carotenoids, N, P andK% in leaves comparing with the control. Raising the salt concentration in irrigation water up to 6000 ppmresulted in an insignificant reduction in most of the studied characters as compared to the control, whereashigher salt concentrations of 9000 and 12000 ppm recorded significant reduction. Total carbohydrates, Na, Cl,Ca, proline and activity of ascorbate peroxidase, catalase, superoxide dismutase and peroxidase in leaves wereincreased by raising the salt concentration in irrigation water salinity compared to the control. Plants receivingAM+R inocula gave the significantly highest mean values for most of the studied characteristics followed byplants receiving AM inoculum, then that inoculated with R inoculum, whereas uninoculated plants (control)gave the lowest values. On contrary uninoculated plants had the highest values of Na, Ca and Cl% in theirleaves followed by that inoculated with R, AM and AM+R inocula. It can be concluded that AM+R treatmentwas the best inoculum tested for improving tolerance of Vachellia farnesiana plants grown in sandy soil toirrigation water salinity up to 6000 ppm without significant reduction than the plants irrigated with tap water.The anatomical study proved this conclusion because of showing an obvious increase in number of stomataon the upper surface of leaf blade and prominent increments in thickness of leaf blade, palisade tissue, spongytissue as well as midrib over than those of control.