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A greenhouse experiment was conducted to investigate the effects of water deficit on growth and physiological parameters of Ficus benjamina and Conocarpus erectus. The results revealed that all growth parameters such as plant height, stem diameter, no. of leaves, no. of branches and chlorophyll contents significantly decreased under water deficit condition. Interestingly, although leaf, stem and total biomass production and allocation decreased significantly under water deficit, but root biomass production and allocation increased significantly. Similarly, stomatal conductance to water vapor decreased significantly and CO2 assimilation rate remained similar to control under water deficit condition. Resultantly, a significant increase in water use efficiency was evident in both species under water deficit condition. These results suggested that, in spite of a significant decrease in biomass production, young Conocarpus erectus and Ficus benjamina can tolerate water deficit which is due to sustained CO2 assimilation rate and increase in root biomass.

Low water availability predicted under climate change is a major abiotic factor limiting plants growth and productivity. In this study a greenhouse experiment was conducted on three important tree species of arid environment: Conocarpus erectus (CE), Acacia modesta (AM), and Salix tetrasperma (ST). Young saplings were subjected to control (C), medium (MWD) and severe soil water deficit (SWD) treatments and response was evaluated. Results showed that in all the three species leaf, stem and root dry weight production remained similar to C under MWD treatment but decreased significantly under SWD. The highest decrease in total dry weight was noticed in ST and the lowest was evidenced in AM under SWD. Root:shoot ratio increased significantly in both CE and AM under MWD and SWD. Furthermore, chlorophyll content decreased while proline content increased significantly in both MWD and SWD treatments. The production of oxidants (hydrogen peroxide and superoxide anions) and antioxidants (superoxide dismutase, catalase, peroxidase and ascorbate peroxidase) increased significantly under both MWD and SWD treatments and were the highest in AM in both MWD and SWD treatments. Therefore, we may conclude that all the three species can tolerate medium water stress due to increased root production and an effective antioxidant defense mechanism.

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Soils polluted by organic or inorganic pollutants are an emerging global environmental issue due to their toxic effects. A phytoremediation experiment was conducted to evaluate the extraction potential of three European aspen clones (R2, R3, and R4) and seven hybrid aspen clones (14, 27, 34, 134, 172, 191, and 291) grown in soils polluted with hydrocarbons (includes polycyclic aromatic hydrocarbons (PAH) and total petroleum hydrocarbons (TPH)). Height growth, plant survival rates, and .hydrocarbon removal efficiencies were investigated over a 4-year period at a site in Somerharju, Luumaki Finland, to assess the remediation potential of the clones. Hydrocarbon content in the soil was determined by gas chromatography and mass spectrometry. The results revealed that hybrid aspen clones 14 and 34 and European aspen clone R3 achieved greater height growth (171, 171, and 114 cm, respectively) than the other clones in the study. Further, the greatest removals of PAH (90% at depth 10-50 cm) and (86% at depth 5-10 cm) were observed in plot G15 planted with clone R2. Furthermore, the greatest TPH removal rate at 5-10 cm depth (C 22-C 40 , 97%; C 10-C 40 , 96%; and C 10-C 21 , 90%) was observed in plot 117 with clone 134. However, other clones demonstrated an ability to grow in soils with elevated levels of TPH and PAH, which indicates their tolerance to hydrocarbons and their potential capacity for phytoremediation of hydrocarbon-polluted soils. Our study suggests that European aspen and hybrid aspen clones could be used for the remediation of soils polluted with PAH and TPH.

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Fruit tree culture is at the brink of disaster in arid to semi-arid regions due to low water availability. A pot experiment was carried out to analyze whether foliar application of salicylic acid (SA) can improve water stress tolerance in Syzygiumcumini. Saplings were subjected to control (CK, 90% of field capacity, FC), medium stress (MS, 60% of FC) and high stress (HS, 30% of FC) along with foliar application of 0.5 and 1.0 mM of SA. Results showed that soil water deficit significantly decreased leaf, stem and total dry weight, leaf gas exchange attributes and chlorophyll a, b. However, root dry weight and root/shoot ratio increased under MS and HS, respectively. Contrarily, foliar application of SA significantly improved chlorophyll a, b, leaf gas exchange attributes, and dry weight production under soil water deficit. Concentration of oxidants like hydrogen peroxide and superoxide radicals, along with malondialdehyde and electrolyte leakage increased under soil water deficit; however, decreased in plants sprayed with SA due to the increase in the concentration of antioxidant enzymes like superoxide dismutase, peroxidase, catalase and ascorbate peroxidase. Results suggest that the foliar application of SA can help improve water stress tolerance in Syzygiumcumini saplings; however, validation of the results under field conditions is necessary.