Abstract
Salinity is one of the main abiotic stress factors which limit the growth and productivity of plants, however, the nutritional status of plants is the first brick in the resistance wall against stresses. Therefore, a factorial experiment was undertaken to investigate effects of soil applied humic acid (0, 7, 14, 21 l.ha-1) and boron foliar spraying (0, 50, 100 ppm) and their interaction on growth and yield of melon plant under saline conditions. The results suggested that the treatments soil application of humic acid and the boron spraying successfully mitigated the deleterious effects of salt stress and influenced growth and yield of melon plant. Humic acid at 21 l.ha-1 or boron spray at 50 ppm exhibited an improvement in growth and yield of melon, in terms of plant length, plant fresh and dry mass, chlorophyll (SPAD), fruit mass, total yield, and also leaf nutrient content (N and K) and total soluble solids (TSS) of fruits, while reduced the sodium content of leaves. The combined treatment of humic acid at 21 l.ha-1 and boron spraying at 50 ppm was found to be more effective for the melon plant to improving growth performance and the crop yield by 21 % as compared with the control group under saline conditions.
Highlights
Salinity of both soil and water in the arid and semi-arid regions is one of the major concerns facing the development in the agricultural sector in these regions, higher salt concentrations and excess exchangeable sodium in the soil has led to the deterioration of soil structure and make plants suffer more, the harmful effects of salinity on plants occur due to its adverse effects on osmotic potential, photosynthesis and protein synthesis (Ouni et al, 2014)
Romero et al 1997, Kaya et al 2007 observed a significant decrease in the plant growth, fresh mass, fruit yield, contents of Ca, K and N, and chlorophyll, as well as the rates of photosynthesis and transpiration, while the Na uptake has increased in the melon plant under salt stress conditions
Increasing concentrations of humic acid caused a gradual increase in the vegetative growth parameters in terms of plant length, leaf chlorophyll reading (SPAD), and fresh and dry mass as compared with the control group
Summary
Salinity of both soil and water in the arid and semi-arid regions is one of the major concerns facing the development in the agricultural sector in these regions, higher salt concentrations and excess exchangeable sodium in the soil has led to the deterioration of soil structure and make plants suffer more, the harmful effects of salinity on plants occur due to its adverse effects on osmotic potential, photosynthesis and protein synthesis (Ouni et al, 2014). Boron is one of the essential micronutrient elements, boron in the proper concentration has several physiological roles within the plant including the function and integrity of cell walls and membranes, sugar transport, differentiation, and root elongation, as well as the metabolism of protein, carbohydrate, nucleic acid, and indole acetic acid (Pinho et al, 2010), plays a vital role in the division and elongation of plant cells as well as in the osmotic adjustment, metabolism of phenols and oxidative stress (Naeem et al, 2017) It is necessary for the flowering and fruiting processes, from the germination of pollen and growth of pollen tube to growth and development of fruit (Krudnak et al, 2013), enhances the nutrient status, marketable yield and shelf life of fruits (Davis et al, 2003). The availability of boron element decreases when the soil pH is higher than 7 in the saline-alkaline soil (Brady, 1990), boron deficiency has an unfavorable impact on the physiological processes of plants, diminishing growth and yield of plants (Pinho et al, 2010)
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