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Drought conditions may have direct or indirect effects on plant physiology, biochemistry, and molecular characteristics. The purpose of this study was to investigate the effects of drought stress on the physiological, biochemical, and molecular responses of three different watermelon cultivars with varying levels of drought tolerance (24: drought resistant, CS: moderately tolerant, and 98: drought sensitive). The cultivars exhibited different responses to cope with water stress according to their tolerance level. Drought induced significant reductions in chlorophyll <em>a</em>, total chlorophyll and carotenoid content and glutation reductase and ascorbate peroxidase activity in the sensitive cultivar unlike in the moderately tolerant and drought resistant cultivars. Additionally, the expression levels of <em>NAC1</em>, <em>NAC2</em>, <em>ORE1</em>, <em>WRKY24</em>, <em>SAG12</em>, <em>SAG13</em>, <em>KCS2</em>, <em>CER1</em>, <em>DREB2A</em>, <em>LTP3</em>, <em>SWEET15</em>, and <em>PYL9</em> genes were measured using qRT-PCR. The expression ratios of the genes significantly varied depending on the gene location and on the tolerance of the cultivars. Results showed that the physiology and biochemical and molecular pathways of tolerant cultivars change to adapt to drought conditions. Therefore, the drought-resistant cultivar copes with drought stress by increasing proline content and antioxidant enzyme activities, as well as by increasing the expression of specific genes.

Determination of heterosis and heterobeltiosis values of salt-tolerant summer squash (Cucurbita pepo L.) genotypes and genetic relationships of parental genomes -779 -

Water scarcity is one of the most pressing problems facing countries in the semi-arid and arid regions of the world. Data predicts that by 2030, global water consumption will increase by 50%, leading to severe water shortages. Today, agricultural production consumes more than 70% of fresh water in many parts of the world, increasing the pressure on water scarcity. For these reasons, agricultural production models and approaches should be developed to reduce water consumption. One developed approach is the use of hydrogel to reduce water consumption and have a positive effect on plant growth. This study investigated the use of hydrogels as chemical components that can be used in water shortage conditions and against the expected water scarcity. Parsley was used as the model organism. The method used was as follows: two different water treatments (50% and 100%) and four different hydrogel concentrations (0%, 50%, 75%, and 100%) were applied, and root width and length, leaf width and length, main stem length, and the number of tillers were measured. According to the results, while no improvement was observed in the plants with 100% hydrogel concentration, the best results were obtained from 50% hydrogel application. The results obtained from 75% hydrogel application were found to be higher than those of 100% hydrogel but lower than 0% hydrogel application. With 50% hydrogel (water-restricted), all plant growth parameters were higher compared to the plants with 100% (full irrigation) water application. It was determined that the average value of the I1 (50%) irrigation was the highest (3.6), and the average value of the I2 (100%) irrigation (2.4) was the lowest. It was determined that the highest average value (6.2) in all measured traits was the average value of the H1 (50%) application, and the lowest average value (0.0) was in the H3 hydrogel applications (100%). In conclusion, this study suggested that hydrogel application is beneficial on a large scale, can optimize water resource management for higher yields in agriculture, and has a positive effect on agricultural yield under water deficit stress.

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