This research was carried out to determine effectiveness of nitric oxide (NO) on some physiological and biochemical reactions, and water use efficiency (WUE) of chard (Beta vulgaris L. var. cicla) under well-watered and drought conditions. NO solutions were prepared with four doses (0, 50, 100, 150 and 200 µM) of sodium nitroprusside as a nitric oxide donor and exogenously applied on only seeds (s) or together with seed and foliar (sf) of chard under different levels of drought according to 100 (control), 67 and 33% of the water required to reach field capacity. NO mitigated the negative effects of drought stress on fresh and dry weights of leaf and root, chlorophyll content, gas exchange parameters and electrical leakage in all doses, especially for doses of 100 and 150 µM for both s and sf applications. Higher antioxidant enzyme content was observed with the application of NO especially under well-watered conditions. Mild drought conditions caused a desirable increase on WUE of the chard.

Peat is a spongy substance which is an effect of incomplete decomposition of plant residues in different stages of decomposition. Between the several organic matters which are used as substrate for horticultural plants cultivation in soilless conditions, peat is the unabandonable ingredient for mixtures for commercial production of plants. Peat is used in horticulture as a component of garden plant substrates, in agriculture for the production of garden soil and as an organic fertilizer, and in balneology as a material for baths and wraps. The use of peat for agriculture and horticulture is determined by the following quality parameters: the degree of decomposition, ash content, pH, the presence of carbonates, the density of the solid phase, bulk density, and porosity. As an organic material, the peat forms in the acidic, waterlogged, and sterile conditions of fens and bogs. The conditions seem like the development of mosses. The plants do not compose as they die. Instead of this, the organic matter is laid down and accumulates in a slow time as peat due to the oxygen deficiency in the bog. This makes peat a highly productive growing medium. In the present novel review, we discuss the peat use in horticulture.

Water use efficiency (WUE) is considered as an important component of adaptation to drought stress. This study was conducted to determine the effect of drought stress on gas exchange parameters and selected physiological properties, and also its relations with WUE in summer squash seedlings (Cucurbita pepo L.). Plants were grown in pots under different irrigation levels (D0: 100%, D1: 67% and D2: 33% of the water required to reach the field capacity) in controlled greenhouse. The results show that drought treatments significantly decreased the leaf chlorophyll reading values (LCRV), leaf relative water content (LRWC), stomatal conductance (g_s), photosynthetic rate (P_N), transpiration rate (T_r), fresh weight (FW) and dry weight (DW) of squash seedlings by 7, 42, 69, 62, 62 63 and 82%, respectively, in D2 treatment compared to D0. However, electrolyte leakage (EL) values increased 72% with severe drought treatments (D2). The highest WUE was obtained by D0 treatment as 0.26 g mm⁻¹. The relationship between P_N and WUE is the strongest one among all leaf gas exchange parameters. Together with T_r, the linear relation with WUE was considerably higher compared to other measured parameters.

Salinity causes yield and quality losses in agricultural production and therefore great economic losses around the world. Hydrogen sulfide (H₂S) is known to play a crucial role to ease physiological and metabolic processes in plants, and also increases the tolerance of the plant against many abiotic stress conditions. In this study, we investigated the effects of H₂S treatments (0, 25, 50, 75 and 100 µM NaHS were applied as H₂S donor) to the tomato seedlings to alleviate the harmful effects of salt stress (0, 75 and 150 mM NaCl). There was a significant decrease in plant growth and development in parallel with the increased salt level. Visible changes in plant development were observed after the dose of 75 mM NaCl in the tomato seedling. The effects of different doses of exogenous H₂S treatment were found to be significant. H₂S treatment increased the stress tolerance in tomato seedlings by arranging the mineral element and hormone content. Furthermore, H₂S relieved the effect of stress in plants by increasing photosynthetic activity (photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductivity (gs) and intercellular CO₂ concentration (Ci)) of the plant. In addition, the effect of H₂S on salt stress tolerance in tomato seedlings may be due to its positive effect on mineral element contents. As a result, based on the beneficial effects of H₂S in tomato seedlings under salt stress, this treatment can be considered as an alternative resilience method for cultivation in saline soils or irrigation with low quality waters.

This study was conducted to evaluate the influence of cadmium (Cd) (0, 100, 150 and 200 mg kg-1) and lead (Pb) (0, 1000, 1500 and 2000 mg kg-1) on morphological, physiological and biochemical responses of rocket (Eruca sativa L.) in greenhouse conditions. Plant growth, some physiological (membrane permeability, relative water content, stomal conductance, etc.) and biochemical (antioxidant enzyme activity, proline and sucrose content) parameters of rocket plants were altered with Cd and Pb levels. The Cd and Pb content in rocket increased with elevated concentration. Both Cd and Pb stress conditions negatively affected plant growth, photosynthetic activity and chlorophyll content. The negative effect of heavy metals elevated with increased doses of Cd and Pb. The treatment of Cd and Pb significantly elevated antioxidant enzyme activities. Furthermore, the heavy metal stressed plants had more malondialdehyde (MDA), hydrogen peroxide (H2O2), proline and sucrose as compared to control plants. This study indicated that rocket plants developed defense mechanisms by regulating enzyme activity and osmolyte accumulation against heavy metal stress.