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Crop plants, such as watermelon, suffer from severe Aluminum (Al3+)-toxicity in acidic soils with their primary root elongation being first arrested. However, the significance of apoplastic or symplastic Al3+-toxicity in watermelon root is scarcely reported. In this work, we identified a medium fruit type (ZJ) and a small fruit type (NBT) as Al+3-tolerant and sensitive based on their differential primary root elongation rate respectively, and used them to show the effects of symplastic besides apoplastic Al distribution in the watermelon's root. Although the Al content was higher in the root of NBT than ZJ, Al+3 allocated in their apoplast, vacuole and plastid fractions were not significantly different between the two cultivars. Thus, only a few proportion of Al+3 differentially distributed in the nucleus and mitochondria corresponded to interesting differential morphological and physiological disorders recorded in the root under Al+3-stress. The symplastic amount of Al+3 substantially induced the energy efficient catalase pathway in ZJ, and the energy consuming ascorbate peroxidase pathway in NBT. These findings coincided with obvious starch granule visibility in the root ultra-structure of ZJ than NBT, suggesting a differential energy was used in supporting the root elongation and nutrient uptake for Al+3-tolerance in the two cultivars. This work provides clues that could be further investigated in the identification of genetic components and molecular mechanisms associated with Al+3-tolerance in watermelon.

Salinity is a negative abiotic stress that produces drastic disorders on soils and plants causing a critical reduction in plant growth and yield parameters, particularly maize plant, which ...

The involvement of natural and eco-friendly alternatives in agriculture has acquired great importance to reduce the harmful effects of excessive and indiscriminate use of agrochemicals. In this regard plant growth-promoting rhizobacteria (PGPR) represented a useful and promising means for sustainable management of plant disease. PGPR are proved their aptitude to save the plant before the establishment of the pathogen within the pathosystem interplay model, this ability is the central point in the effective management of plant disease. They protect the plant in two ways; the first one is directive when competing for plant pathogens for nutrients and niches and suppressing their growth through secretion of a vast range of antimicrobial compounds. Meanwhile, the second way is indirect when they induce systemic resistance against plant pathogens and strengthen plant health. This chapter will offer an extensive discussion about these microorganisms, their direct and indirect interaction mechanisms with plant-pathogen pathosystem, recent progress, and prospects in the application of this auspicious approach for sustainable agriculture production.

Melatonin (MT) is a pleiotropic molecule with diverse and numerous actions both in plants and animals. In plants, MT acts as an excellent promotor of tolerance against abiotic stress situations such as drought, cold, heat, salinity, and chemical pollutants. In all these situations, MT has a stimulating effect on plants, fomenting many changes in biochemical processes and stress-related gene expression. Melatonin plays vital roles as an antioxidant and can work as a free radical scavenger to protect plants from oxidative stress by stabilization cell redox status; however, MT can alleviate the toxic oxygen and nitrogen species. Beyond this, MT stimulates the antioxidant enzymes and augments antioxidants, as well as activates the ascorbate–glutathione (AsA–GSH) cycle to scavenge excess reactive oxygen species (ROS). In this review, we examine the recent data on the capacity of MT to alleviate the effects of common abiotic soil stressors, such as salinity, alkalinity, acidity, and the presence of heavy metals, reinforcing the general metabolism of plants and counteracting harmful agents. An exhaustive analysis of the latest advances in this regard is presented, and possible future applications of MT are discussed.

Water stress (drought and waterlogging) is drastic abiotic stress to plant growth and development. Melatonin, bioactive plant hormone, has been widely tested in drought situations in diverse plant species, while a few studies on the role of melatonin in waterlogging stress conditions have been published. In the current review, we analyze the bio-stimulatory functions of melatonin on plants under both drought and waterlogging stress. Melatonin controls the levels of reactive oxygen and nitrogen species and positively changes the molecular defense to improve plant tolerance against drought and waterlogging stress. Moreover, the crosstalk of melatonin and other phytohormones is a key element on plant survival under drought stress, while this relationship needs further investigation under waterlogging stress. In this review, we draw the complete story of water stress on both sides: drought and waterlogging through discussing the previous critical studies under both conditions. Moreover, we suggest several research directions, especially for waterlogging, which remains a big vague piece of melatonin and water stress puzzle.

Boron (B) is a microelement required in vascular plants at a high concentration that produces excess boron and toxicity in many crops. B stress occurs widely and limits plant growth and crop productivity worldwide. Salicylic acid (SA) is an essential hormone in plants and is a phenolic compound. The goal of this work is to explore the role of SA in the alleviation of excess B (10 mg L&minus, 1) in watermelon plants at a morphological and biochemical level. Excess boron altered the nutrient concentrations and caused a significant reduction in morphological criteria, chlorophyll a, b, and carotenoids, net photosynthetic rate, and the stomatal conductance and transpiration rate of watermelon seedlings, while intercellular carbon dioxide (CO2) was significantly increased compared to the control plants (0.5 mg L&minus, 1 B). Furthermore, excess boron accelerated the generation of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) and induced cellular oxidative injury. The application of exogenous SA significantly increased chlorophyll and carotenoid contents in plants exposed to excess B (10 mg L&minus, 1), in line with the role of SA in alleviating chlorosis caused by B stress. Exogenously applied SA promoted photosynthesis and, consequently, biomass production in watermelon seedlings treated with a high level of B (10 mg L&minus, 1) by reducing B accumulation, lipid peroxidation, and the generation of H2O2, while significantly increasing levels of the most reactive ROS, OH&minus, SA also activated antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) and protected the seedlings from an ROS induced cellular burst. In conclusion, SA can be used to alleviate the adverse effects of excess boron.

Metal-contaminated soils are considered a global concern due to their adverse effects on ecosystem vitality. This study was conducted to assess the efficiency of garden waste biochar (GB), as a modern remediation tool of soils contaminated with heavy metals (HMs), compared with the other Paulownia biochar (PB) and bamboo biochar (BB), on the growth of Brassica juncea (L.). The experiments and analyses were carried out at the Institute of Agricultural Resources and Environment, Guangdong Academy of Agricultural Sciences (Guangzhou, China), during the year 2018. The studied contaminated soil sample was amended with 0, 2%, 4%, and 6% (w/w) of PB, BB, GB400, and GB600 biochar. The experiment was designed in a completely randomized block design with 3 replications for each treatment. Garden waste biochar significantly duplicated the soil organic matter and EC 1.43−2.21 and 1.33−1.51 times, respectively, enhanced soil pH, and improved plant growth. It was more efficient to improve soil properties than PB and BB. DTPA-extractable metals showed the highest reduction at 6% of GB400, which was 29.56, 46.04, and 59.98% for Pb, Cd, and Cu, respectively, while it was 48.29% for Zn at GB600 over the control. Moreover, GB treatments increased the nitrogen (N) and phosphorus (P) contents of the plant shoots. Besides, HM contents of soil and plant tissues were significantly reduced after biochar applications and the highest reduction was recorded using 6% of GB. The results obviously pointed out that the metal transfer coefficient (TC) of shoots was decreased compared with the control after biochar applications, and GB showed the optimum response in this regard. The huge amounts of garden waste, after transforming them to biochar (GB) which has been considered more effective in safe crop production, can be used to reduce the availability of toxic metals in the soil and keep them under safe limits, especially with large-scale vegetable crops in China. It will clean the environment and improve resource sustainability. Therefore, GB is recommended to be used in soil HM remediation on a large scale in polluted areas.

Crop plants, such as watermelon, suffer from severe Aluminum (Al

The present work reveals the beneficial role of sodium nitroprusside (SNP, NO donor concentration: 50 and 100 &micro, M) in mitigation of water stress accompanied by a reduction in viral disease incidence in tomato plants subjected to deficit irrigation. The plants were grown under two irrigation regimes: well-watered (WW, irrigated after the depletion of 55&ndash, 60% of available soil water) and water deficit (WD, irrigated after the depletion of 85&ndash, 90% of available soil water) in two seasons of 2018 and 2019. The results indicated that under water stress conditions, plant growth, chlorophyll, relative water content (RWC), and fruit yield were decreased. Conversely, water stress significantly increased the MDA, proline, soluble sugars, and antioxidant enzymes&rsquo, activities. Moreover, it was obvious a negligible increase in the fruit content from NO2 and NO3. Water-deficit stress, however, had a positive impact on reducing the percentage of viral disease (TMV and TYLCV) incidence on tomato plants. Similarly, SNP application in the form of foliar spray significantly reduced the disease incidence, the severity, and the relative concentrations of TMV and TYLCV in tomato plants raised under both WW and WD conditions. The treatment of SNP at 100 &micro, M achieved better results and could be recommended to induce tomato plant tolerance to water stress. Thus, the present work highlights the role of NO (SNP) in the alleviation of water stress in tomato plants and subsequent reduction in viral disease incidence during deficit irrigation.

Although boron deficiency (BD) is a drastic disorder to the agriculture crops, its effects on watermelon still unknown. Therefore, the present study investigates the effect of BD (0 and 0.5 mg L−1) on different morphological, physiological and biochemical traits, and mineral uptake during early seedlings stage of watermelon. B-deficiency induced leaf chlorosis in watermelon initiated from the leaf margins and tips. Despite that, BD increased shoot length, and root and shoot dry weight of BD-watermelon seedlings. BD decreased leaf chlorophyll and carotenoid contents, and photosynthetic parameters without affecting quantum yield of PSII. BD significantly inhibited total soluble protein accumulation, while leaf proline content was unaffected. A significant increase in antioxidant enzyme activities in response to higher hydrogen peroxide (H2O2) generation could possibly reduced lipid peroxidation and promoted BD-watermelon plant growth. BD influenced mineral uptake variously: the induction of phosphor...