The chloroplast has a central position in oxygenic photosynthesis and primary metabolism. In addition to these functions, the chloroplast has recently emerged as a pivotal regulator of plant responses to abiotic and biotic stress conditions. Chloroplasts have their own independent genomes and gene-expression machinery and synthesize phytohormones and a diverse range of secondary metabolites, a significant portion of which contribute the plant response to adverse conditions. Furthermore, chloroplasts communicate with the nucleus through retrograde signaling, for instance, reactive oxygen signaling. All of the above facilitate the chloroplast’s exquisite flexibility in responding to environmental stresses. In this review, we summarize recent findings on the involvement of chloroplasts in plant regulatory responses to various abiotic and biotic stresses including heat, chilling, salinity, drought, high light environmental stress conditions, and pathogen invasions. This review will enrich the better understanding of interactions between chloroplast and environmental stresses, and will lay the foundation for genetically enhancing plant-stress acclimatization.
Greenhouse and aquaponic productions of basil (Ocimum basilicum L.) are well established, but the comparison between these two methods is not studied in detail. A study was conducted to evaluate the performance of basil in both aquaponic and soil systems under greenhouse conditions. The plants were raised in aquaponic beds with ornamental fish and a set of plants was raised in soil pots under a greenhouse setup. The studied parameters were morphological, biochemical and antioxidant levels. In order to analyze the stress effects of an aquaponic system on plant defense mechanism, two different antioxidant enzymes (catalase and peroxidase) were analyzed. Water quality parameters were monitored during the entire study period. Based on the results, there was a significant increase in growth parameters in the aquaponic system when compared to the conventional greenhouse cultivation of basil plants. The photosynthetic parameters showed a decline in the aquaponic system, but the biochemical parameters showed an enhancement in the aquaponic system of growing basil plants. The antioxidants exhibited a significant increase in the aquaponic system, which suggests a water stress effect on the plants induced by the aquaponic growing system. From the results of this study, it can be concluded that the aquaponic system is the best suitable method for basil production in the UAE condition.
Medicinal herbs are potential sources of biomolecules and their analogues that have great relevance in the preparation of modern medicines. Calligonum crinitum, a perennial shrub growing in the United Arab Emirates, has been utilized in the study to validate the therapeutic properties exploited in the traditional medicinal system of UAE. The phytochemical screening of the plant employing different solvents of methanolics and ethyl-acetates, expressed varied proportions of monosaccharides and carbohydrates along with tannins and saponins, which are high potency molecules for therapeutic applications. The presence of total phenol and flavonoid contents derived from methanolic extracts indicates antioxidant potentials and the defense mechanisms of the plant. Proximate and mineral nutrient analysis validates the significance of the extracts with a high amount of carbohydrates and proteins along with significantly high amounts of Zn, Fe, Mn, Ca, Mg and K involved in various metabolic reactions. Similarly, the ABTS radical scavenging activity varied significantly (p < 0.05) and ranged from 10 to 160 µg GAE/g in the methanolic extract. DPPH free radical scavenging activity exhibited a significantly high DPPH activity in methanolic extracts with free radical scavenging activity of 72%. Hydroxyl radicals scavenging activity was also found to be high in the Calligonum extracts along with SOD (49–83%, compared to the standard GAE 37–58%). Nitric oxide scavenging was also found to be high in the extracts, thereby decreasing the content of NO. Thus, our results confirm that the derived extracts have potential antioxidants, and this legitimizes their use in folkloric medicine. These results are highly significant as they can pave the way for future scientific validation of the traditional knowledge of this important medicinal plant.
The essential oil (EO) of the desert cotton (Aerva javanica (Burm. f.) Juss. ex Schul.) was extracted by hydrodistillation, from A. javanica flowers growing in the sandy soils of the United Arab Emirates (UAE) wild desert. The influence of seasonal variation on flowers’ EO yield was studied. The flowers’ EO yield obtained from spring samples (0.011%) was significantly the highest followed by early summer (0.009%), winter (0.007%), and autumn samples (0.006%), respectively. The flowers’ EO antioxidant analysis were tested by DPPH, FRAP and ABTS assays (in vitro). Results proved that A. javanica flowers’ EO, isolated during the four seasons, is a good source of natural bioactive antioxidants. Based on the three tested assays, the highest antioxidant activity was recorded in the spring. Testing of the chemical composition of the flowers’ EO was conducted for the season with the highest yield and the best antioxidant performance, recorded in spring, by a combination of gas chromatograph (GC) and gas chromatograph-mass spectrometer (GC-MS). This led to the identification of 29 volatile components, in which the flowers’ oil was characterized by angustione as a major compound. Photos by scanning electron microscope (SEM) showed prominent availability of star-shaped trichomes in the epidermis of the flowers.
Essential Oils (EOs) are expensive hydrocarbons produced exclusively by specific species in the plant kingdom. Their applications have deep roots in traditional herbal medicine, which lacks scientific evidence. Nowadays, more than ever, there is a growing global interest in research-based discoveries that maintain and promote health conditions. Consequently, EOs became a much attractive topic for both research and industry, with revenues reaching billions of dollars annually. In this work, we provide key guidance to all essential oil-bearing plants growing in the United Arab Emirates (UAE). The comprehensive data were collected following an extensive, up-to-date literature review. The results identified 137 plant species, including indigenous and naturalized ones, in the UAE, citing over 180 published research articles. The general overview included plant botanical names, synonyms, common names (Arabic and English), families and taxonomic authority. The study acts as a baseline and accelerator for research, industry and discoveries in multiple disciplines relying on essential oil-bearing plants.
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