Heat stress is an environmental problem that can negatively impact tomato productivity by reducing fruit setting and disrupting pollen development. The present study aims to understand the molecular mechanism of heat tolerance induced by L-ascorbic acid. Plants were grown in the summer of 2022 (day and night temperatures were 34.4°C and 25.2°C respectively). The plants were divided into two groups: one was sprayed with L-ascorbic acid (0.5 mM) and the other served as a control. Growth parameters, antioxidant enzymes, proline, hydrogen peroxide, and malondialdehyde levels in the leaves were determined. Additionally, a molecular docking allowed understanding the interaction between the antioxidant enzymes and L-ascorbic acid. Results indicated that L-ascorbic acid increased antioxidant enzyme activities (catalase, peroxidase, ascorbate peroxidase, polyphenol oxidase), proline content, fruit setting and growth indicators (shoot and root fresh and dry weight). It also reduced hydrogen peroxide and malondialdehyde levels in tomato leaves. Furthermore, the in-silico analysis revealed that L-ascorbic acid binding energies toward antioxidant enzymes were similar to those of known activators. In conclusion, foliar application of L-ascorbic acid (0.5 mM) effectively mitigated heat stress effects, activating antioxidant enzymes and eliminating reactive oxygen species, ultimately resulting in increased fruit setting.

This study was to evaluate the activity of peroxidase, polyphenoloxidase, pectin methyl esterase and protease as well as the proximate chemical composition and quality parameters of cactus pear and papaya which were dried by different methods and stored for 6 months. Our findings revealed that the highest moisture content was recorded in osmo – freeze drying of papaya and cactus pear. On the other hand, the browning index of oven dried papaya and cactus pear was higher than those dried with osmotic dehydration and osmo – freeze drying. The less activity of peroxidase was recorded in osmo – freeze drying of papaya and cactus pear. Also, the highest reduction of polyphe-noloxidase activity was noticed in osmo–freeze drying methods. While oven dried pa-paya recorded the highest activity of pectin methyl esterase pectin (0.34 %), complete in-activation was shown in other dried methods after 6 months of storage at 4 ±1℃. Different dried methods of papaya caused to reduce the activity of protease, moreover, complete inac-tivation was observed after 3 months from storage. The quality parameters for sensory evaluation of dried cactus pear and papaya demonstrated that osmo–freeze drying was more favorable to preserve samples followed by osmotic dehydration and oven drying.

Biological experiments were carried out at Agronomy Seed Lab., Agronomy Dept., Faculty of Agriculture, Ain Shams University and Ain Shams Center For Genetic Engineering and Biotechnology ACGEB, Genetic Dept., Faculty of Agriculture, Ain Shams University during 2016/2017 season. Priming and its duration were investigated whereas different types of priming (hydro-priming, osmopriming and salt-priming) and different periods of each type (short- medium and long periods) were stuied. Newly harvested soybean seeds cultivar (Giza 111) were submitted from Field Crop Institute, Agricultural Research Center (ARC). It was found that type of priming enhanced germination percentage significantly from low performance of 40% to 51%, 68% and 75.5% for hydration, osmopriming and salt priming respectively. Extending exposing period to the longest period gave significantly maximum increment in seed germination. Maximum germination enhancement was achieved when calcium chloride solution was used for the longest period (48 hrs.) giving value of 96.0%. Such increment reached 140% as compared with control.  It was noticeable that increasing soaking period to the longest period examined in this investigation accelerated the rate of germination to a maximum level. Salt priming produced longest soybean seedling shoot when compared with control. Overall, for most results obtained in this trial,   seed primed with CaCl2 showed better perfor mance than those primed with water or PEG solution.  Seedling dry weight revealed a significant effect in a similar manner of seedling length. The longest exposing priming period showed a significant effect on seedling dry weight. Soybeans seeds proteins exposed to priming for all three periods used in this investigation varied from control, whereas number of protein bands on SDS gel increased from 10 bands separated on control pattern to 13, 11 and 12 for hydration treatment at periods of 6, 12 and 24 hrs., respectively. Also number of mono poly-uni. and unique bands varied as well as its intensive dye which reflect that amount of protein formed varied between treatments.  Considering exposing seeds to salt solution of CaCl2 for longest period (48 hrs.) less bands of separated protein were formed on SDS gel. Biological seed quality was assessed by extracting proteins on native polyacrylamide gel electrophoresis, whereas, all priming treatment at application periods caused on increasing in peroxidase activity compared to control (untreated seeds).  It was remarkably that the longest period of expose showed the highest peroxidase activity when compare to control and also for the short and medium exposing periods (6 and 12 hrs.). Also it was noticed that there were a unique diffuse band at the end of the lane, these bands were less intensive in staining color, meaning that their activities is less than those extracted from hydro-primed seeds for short and medium periods (6 and 12 hrs. respectively).  Seed esterase activity bands had two prolonged regions, these bands appeared as a diffuse bands. Esterase activity bands of PAGE gel showed less activity as subjected to all priming types at any period used in this investigation (long, medium and short) when compared to untreated seed (control). It was clear that increasing period of exposing seeds to priming reduced esterase activity since the intensive band diminished in their intensive color.

This study aims to evaluate the effect of solar UV radiation on defensive enzymes activities in lettuce seedlings. Seeds of lettuce were grown in high tunnels for 35 days, exposed to three different levels of solar UV, created by using three different types of plastic films. Each plastic film transmits different levels of solar UV (0% in UV-B, 4% in UV-L and 83% in UV-T). The obtained results indicated that solar UV radiation has led to significant decrease in seedling fresh weight. UV-B treatment resulted the highest shoot and root length while UV-T treatments exhibited the highest shoot: root ratio. Solar UV radiations have no effect on peroxidase activity in shoots. While ascorbate peroxidase was activated and catalase was inhibited in shoot by UV-T treatments. In lettuce roots, peroxidase, ascorbate peroxidase, and catalase activities were increased by increasing the level of solar UV radiation. In case of UV-T, phenylalanine ammonia lyase (PAL) activity in both shoots and roots of lettuce seedlings was higher than those of other treatments. In addition, Phenols are accumulated in lettuce shoots as a result of UV radiation in UV-L and UV-T treatments. Also, phenols in roots increased by increasing solar UV dose. The study concluded that solar UV radiation induced some antioxidant enzymes, increased the accumulation and biosynthesis of phenolic compounds and reduced lettuce seedlings growth.