Comparative physiological and full-length transcriptome analyses reveal the molecular mechanism of melatonin-mediated salt tolerance in okra (Abelmoschus esculentus L.).

BACKGROUND: Melatonin, a multifunctional signal molecule, has been reported to play crucial roles in growth and development and stress responses in various plant species. Okra (Abelmoschus esculentus L.) is a food crop with extremely high values of nutrition and healthcare. Recent reports have revealed the protective role of melatonin in alleviating salt stress. However, little is known about its regulatory mechanisms in response to salt stress in okra. RESULTS: In this study, we explored whether exogenous melatonin pretreatment could alleviate salt stress (300 mM NaCl) of okra plants. Results showed that exogenous application of melatonin (50 µM) significantly enhanced plant tolerance to salt stress, as demonstrated by the plant resistant phenotype, as well as by the higher levels of the net photosynthetic rate, chlorophyll fluorescence and chlorophyll content in comparison with nontreated salt-stressed plants. Additionally, melatonin pretreatment remarkably decreased the levels of lipid peroxidation and H2O2 content and scavenged O2•- in melatonin-pretreated plants, which may be attributed to the higher levels of enzyme activities including POD and GR. Moreover, a combination of third- (PacBio) and second-generation (Illumina) sequencing technologies was applied to sequence full-length transcriptomes of okra. A total of 121,360 unigenes was obtained, and the size of transcript lengths ranged from 500 to 6000 bp. Illumina RNA-seq analysis showed that: Comparing with control, 1776, 1063 and 1074 differential expression genes (DEGs) were identified from the three treatments (NaCl, MT50 and MT + NaCl, respectively). These genes were enriched in more than 10 GO terms and 34 KEGG pathways. Nitrogen metabolism, sulfur metabolism, and alanine, aspartate and glutamate metabolism were significantly enriched in all three treatments. Many transcription factors including MYB, WRKY, NAC etc., were also identified as DEGs. CONCLUSIONS: Our preliminary results suggested that melatonin pretreatment enhanced salt tolerance of okra plants for the first time. These data provide the first set of full-length isoforms in okra and more comprehensive insights into the molecular mechanism of melatonin responses to salt stress.

Effect of Abelmoschus esculentus (okra) on metabolic syndrome: A review.

Metabolic syndrome is a disorder characterized by dyslipidemia, insulin resistance, abdominal fat, high blood pressure, hypertriglyceridemia, and diminished high density lipoprotein cholesterol. Okra (Abelmoschus esculentus L.), routinely called lady's finger, has belonged to the Malvaceae family. Okra is considered as a valuable crop due to the multiple functions of its leaves, buds, flowers, pods, stems, and seeds in traditional and modern medicines. Several bioactive components are presented in different parts of okra including polyphenolic compounds especially oligomeric catechins and flavonol derivatives such as quercetin. The antioxidant, anti-inflammatory, anticancer, immunomodulatory, gastroprotective, neuroprotective, lipid lowering, and antidiabetic effects of okra have been established. Although different in vivo and in vitro studies revealed that okra has an ability to overcome metabolic syndrome symptoms, the lack of clinical studies is notable. So, further clinical trials should be accomplished to confirm the role of okra in metabolic syndrome. The aims of this review are to gather different studies regarding the potential efficacy of okra in metabolic syndrome.

Hyperspectral imaging combined with machine learning as a tool to obtain high-throughput plant salt-stress phenotyping.

The rapid selection of salinity-tolerant crops to increase food production in salinized lands is important for sustainable agriculture. Recently, high-throughput plant phenotyping technologies have been adopted that use plant morphological and physiological measurements in a non-destructive manner to accelerate plant breeding processes. Here, a hyperspectral imaging (HSI) technique was implemented to monitor the plant phenotypes of 13 okra (Abelmoschus esculentus L.) genotypes after 2 and 7 days of salt treatment. Physiological and biochemical traits, such as fresh weight, SPAD, elemental contents and photosynthesis-related parameters, which require laborious, time-consuming measurements, were also investigated. Traditional laboratory-based methods indicated the diverse performance levels of different okra genotypes in response to salinity stress. We introduced improved plant and leaf segmentation approaches to RGB images extracted from HSI imaging based on deep learning. The state-of-the-art performance of the deep-learning approach for segmentation resulted in an intersection over union score of 0.94 for plant segmentation and a symmetric best dice score of 85.4 for leaf segmentation. Moreover, deleterious effects of salinity affected the physiological and biochemical processes of okra, which resulted in substantial changes in the spectral information. Four sample predictions were constructed based on the spectral data, with correlation coefficients of 0.835, 0.704, 0.609 and 0.588 for SPAD, sodium concentration, photosynthetic rate and transpiration rate, respectively. The results confirmed the usefulness of high-throughput phenotyping for studying plant salinity stress using a combination of HSI and deep-learning approaches.

Rapid modulation of ultraviolet shielding in plants is influenced by solar ultraviolet radiation and linked to alterations in flavonoids.

The accumulation of ultraviolet (UV)-absorbing compounds (flavonoids and related phenylpropanoids) and the resultant decrease in epidermal UV transmittance (TUV ) are primary protective mechanisms employed by plants against potentially damaging solar UV radiation and are critical components of the overall acclimation response of plants to changing solar UV environments. Whether plants can adjust this UV sunscreen protection in response to rapid changes in UV, as occurs on a diurnal basis, is largely unexplored. Here, we use a combination of approaches to demonstrate that plants can modulate their UV-screening properties within minutes to hours, and these changes are driven, in part, by UV radiation. For the cultivated species Abelmoschus esculentus, large (30-50%) and reversible changes in TUV occurred on a diurnal basis, and these adjustments were associated with changes in the concentrations of whole-leaf UV-absorbing compounds and several quercetin glycosides. Similar results were found for two other species (Vicia faba and Solanum lycopersicum), but no such changes were detected in Zea mays. These findings reveal a much more dynamic UV-protection mechanism than previously recognized, raise important questions concerning the costs and benefits of UV-protection strategies in plants and have practical implications for employing UV to enhance crop vigor and quality in controlled environments.

Responses of growth of lady's fingers (Abelmoschus esculentus L.) to different treatments methods of dairy wastewater.

INTRODUCTION AND OBJECTIVE: Water is one of the most important precious resources found on the earth, and are most often affected by anthropogenic activities and by industry. Pollution caused by human beings and industries is a serious concern throughout the world. Population growth, massive urbanization, rapid rate of industrialization and modern techniques in agriculture have accelerated water pollution and led to the gradual deterioration of its quality. A large quantity of waste water disposed of at sea or on land has caused environmental problems which have led to environmental pollution, economic losses and chemical risks caused by the wastewater, and its impact on agriculture. However, waste water which contain nutrients and organic matter has possible advantages for agricultural purposes. Therefore, the presented study was undertaken to assess the impact of Dairy Effluent (treated and untreated waste water) on seed germination, seedling growth, dry matter production and the biochemical parameters of lady's fingers (Abelmoschus esculentus L.). MATERIALS AND METHODS: A field experiment in a green house was conducted to use raw and treated dairy wastewater for watering lady's fingers (Abelmoschus esculentus L.). The plants were watered using (WW) raw dairy wastewater, (T1) chemicals treatment, (T2) physical treatment, (T3) dilution method treatment and tap water (TW) in pot experiments. Ten plants of each treatment /3 replicate were randomly selected and labelled for the collection of data. The data was collected sequentially, starting with chlorophyll content pre-harvest, vegetative qualities (shoot, root and seedling length) and dry matter quality (shoot and root dry matter) pos-tharvest. RESULTS: The effect was seen on the germination seed and growth of the plant. The results showed inhibitory effect from dairy effluent (WW) on seed germination and plant growth. Treatment with chemicals showed statistically significant differences with other treatments. Chemical treatment (TC2) at 20 mg/L Al2(SO4)3 and pH 6.5 improved all growth characteristics, compared with WW, and TW reached 85%, 70.8 cm, 28.6 cm, 99.4 cm, 65.36%, 15.86% and 3.543 Mg\g FW for seed germination, shoot length, root length, seedling length, shoot dry matter, root dry matter and chlorophyll, respectively. Also, 25% concentration and 6.5 pH from the dilution method treatment improved all the qualities, but at a lower level. A maximum favourable effect was also observed in the (T2) physical treatment, and ranged from average to moderate in terms of impact. CONCLUSIONS: Thus, dairy effluent, after chemical treatment and proper dilution, can be used as a potential source of water for seed germination and plant growth in agricultural practices.

Influence of wastewater application and fertilizer use on growth, photosynthesis, nutrient homeostatis, yield and heavy metal accumulation in okra (Abelmoschus esculentus L. Moench).

The scarceness of freshwater assets is a serious problem in semi-arid zones and marginal quality water is increasingly being used in agriculture. This study aimed at evaluating the physico-chemical and biological risks on irrigated soils of treated wastewater, the nutrient supply and the effect on okra plant. A pot experiment based on completely randomized block design was conducted with Treated Wastewater (TW) and inorganic fertilizers to observe a comparative effect on biochemical characters using Okra var. Nidhi. The physico-chemical analysis of the TW showed that it was rich in total suspended and dissolved solids with large amount of BOD and COD. The higher amount of Cl-, Ca++, Mg++ and K+ were also present in the effluent. The heavy metal (Cd, Cr, Ni and Pb) content in TW is comparatively more than groundwater (GW). The values of these heavy metals were slightly higher in the soil irrigated with TW. The effluent severely affects crop plants and soil properties when used for irrigation. The growth parameters, photosynthetic characteristics, chlorophyll content, yield and nutrient homeostatis were analyzed during different growth periods in all treatments. All the parameters were found to increase due to wastewater application. Among the fertilizer treatments, N120 proved optimum, N90 deficient and N150 proved as luxury dose. The seeds accumulated Cd and Ni but their level was under permissible limits. Thus, it may be concluded that wastewater may be used profitably for the cultivation of okra.

Agro-potentiality of distillery effluent on soil and agronomical characteristics of Abelmoschus esculentus L. (okra).

The present study showed that irrigation of soil with different effluent concentrations (10, 25, 50, 75, and 100 %) of distillery effluent (DE) for 60 days resulted in significant (P < 0.001) changes in moisture content; electrical conductivity (EC), pH, chlorides (Cl(-)), total organic carbon (TOC), exchangeable sodium (Na(+)), available potassium (K(+)), calcium (Ca(2+)), magnesium (Mg(2+)), iron (Fe(2+)), total Kjeldahl nitrogen (TKN), available phosphorus (P), and sulfate (SO4 (2-)) of soil. The non-significant (P > 0.05) changes were observed for water-holding capacity and bulk density of the soil. Among various concentrations of DE irrigation, irrigation with 100 % effluent concentration increased moisture content, (24.85 %), EC (77.88 %), Cl(-) (285.95 %), TOC (3,171.42 %), exchangeable Na(+) (241.04 %), available K(+) (52.49 %), Ca(2+) (990.37 %), Mg(2+) (1,751.72 %), TKN (1,417.00 %), available P (305.00 %), and SO4 (2-) (75.32 %) in the soil and decreased pH (-20.22 %). The more stimulation in agronomical parameters such as shoot length, root length, number of leaves, flowers, pods, dry weight, fresh weight, chlorophyll content, leaf area index, and crop yield of A. esculentus were observed to be inversely proportional to the concentration of effluent water, with the best results being obtained at a dilution of 25 % of DE concentration.

Spectroscopic and thermooxidative analysis of organic okra oil and seeds from Abelmoschus esculentus.

With changes in human consumption from animal fats to vegetable oils, the search for seed types, often from unconventional vegetable sources has grown. Research on the chemical composition of both seed and oil for Brazilian Okra in South America is still incipient. In this study, flour and oil from organic Okra seeds (Abelmoschus esculentus L Moench), grown in northeastern Brazil were analyzed. Similar to Okra varieties from the Middle East and Central America, Brazilian Okra has significant amounts of protein (22.14%), lipids (14.01%), and high amounts of unsaturated lipids (66.32%), especially the oleic (20.38%) and linoleic acids (44.48%). Oil analysis through PDSC revealed an oxidation temperature of 175.2 °C, which in combination with low amounts of peroxide, demonstrates its resistance to oxidation and favors its use for human consumption.

Studies on heterosis in Abelmoschus esculentus (L.) Moench and A. callei (A. Chev) stevels cultivars during shorter day photoperiods in south eastern Nigeria.

Better parent heterosis was studied in direct and reciprocal crosses using 9 early and late okra cultivars which belonged to the Early-early, Early-late, Late-early and Late-late okra flowering types. The ANOVA for length of pod, circumference of pod, number of locules per pod, number of seeds per pod, Number of pods per plant, weight of 1000 seeds, density of seeds, weight of pods per plant, days to flower opening, plant height and circumference of stem at 10 cm above soil level, showed almost very highly significant differences-an indication that the cultivars are genetically diverse. Very highly significant, narrow and intermediate, heterosis was recorded for most of the direct and reciprocal crosses, showing that selections could be made from the hybrids to meet desired local okra qualities. A cross between an Early-late and Late-early parents, using early okra as the maternal parent, gave rise to a stable viable bridge hybrid which outperformed the better parent in many respects thereby overcoming the hitherto strong barrier to gene flow in interspecific hybridization studies involving the two okra types and also indicating the existence of maternal effects. Consequently with this development, the window has been opened for possible accelerated transfer of several desirable genes from late okra types to many promising but vulnerable early okra types. This could result to minimizing the further erosion of such early okra germplasm still in the custody of the local farmers.

Alterations in activities of acid phosphatase, alkaline phosphatase, ATPase and ATP content in response to seasonally varying Pi status in okra (Abelmoschus esculentus).

Phosphorus (P) is the second most important macronutrient for plant growth. Plants exhibit numerous physiological and metabolic adaptations in response to seasonal variations in phosphorus content. Activities of acid and alkaline phosphatases, ATPase and ATP content were studied in summer, rainy and winter seasons at two different developmental stages (28 and 58 days after sowing) in Okra. Activities of both acid and alkaline phosphatases increased manifold in winter to cope up with low phosphorus content. ATP content and ATPase activity were high in summer signifying an active metabolic period. Phosphorus deficiency is characterized by low ATP content and ATPase activity (which are in turn partly responsible for a drastic reduction in growth and yield) and enhanced activities of acid and alkaline phosphatases which increase the availability of P in P-deficient seasons.