Alterations in the Antioxidant Metabolites in Cotton Leaf Curl Disease Infected and Healthy Cotton Leaves

The upland cotton (Gossypium hirsutum) belongs to the family Malvaceae and cultivated since ancient times in warmer parts of the world. Pakistan is the 4th largest cotton producing country and prominent cotton yarn exporter of the world. Cotton is the major source of natural fiber and significantly contributes to the economy of Pakistan. There are many factors (biotic and abiotic) affecting the cotton yield in Pakistan. The cotton leaf curl disease (CLCuD) is one of the biotic factors and endemic in the most cotton growing areas of the country. The antioxidant enzymes and antioxidant biochemical metabolites play important role during stress. The present study was planned to compare the antioxidant enzymes and metabolites from healthy and CLCuD infected cotton leaves. Antioxidant enzymes activities including catalase, peroxidase and peroxidase were measured through different antioxidant assays and different antioxidant metabolites were also determined. During stress condition antioxidant metabolites serve as signal for the activation of antioxidant enzymes. Present study revealed that antioxidant enzymes were significantly higher in the infected cotton leaves as compared to the healthy cotton leaves. While the amount of antioxidant metabolites like total phenolic contents (TPC) and total flavonoid contents (TFC) were higher in healthy cotton leaves as compared to the infected leaves.

Microbial Inoculants Modulate Physiological Behaviour Of Troyer Citrange Under Drought Stress

A study was undertaken with Troyer citrange (Citrus sinensis × Poncirus trifoliata), the rootstock of citrus, to elucidate the interaction effects of arbuscular mycorrhizal fungi and plant-growth-promoting bacteria on plant physiology under both ample watered and water stress conditions. The result exhibited significant influence of Glomus intraradices and phosphorus solubilising bacteria (PSB) (mixture of Bacillus subtilis and B. megatherium) on plant growth due to root-fungus-bacteria interaction leading to reduced accumulation of reactive oxygen species, production of antioxidant metabolites, higher anti-scavenging enzymes and higher acquisition of plant nutrients, besides enhancing rhizosphere microbial activity. Thus, Troyer citrange could be co-inoculated with G. intraradices and PSB during propagation for healthy growth of the seedlings thereby pre-ponding the budding and subsequent establishment of composite plants under field conditions. Bangladesh J. Bot. 50(3): 467-474, 2021 (September)

Antioxidant Metabolites in Primitive, Wild, and Cultivated Citrus and Their Role in Stress Tolerance

The genus Citrus contains a vast range of antioxidant metabolites, dietary metabolites, and antioxidant polyphenols that protect plants from unfavorable environmental conditions, enhance their tolerance to abiotic and biotic stresses, and possess multiple health-promoting effects in humans. This review summarizes various antioxidant metabolites such as organic acids, amino acids, alkaloids, fatty acids, carotenoids, ascorbic acid, tocopherols, terpenoids, hydroxycinnamic acids, flavonoids, and anthocyanins that are distributed in different citrus species. Among these antioxidant metabolites, flavonoids are abundantly present in primitive, wild, and cultivated citrus species and possess the highest antioxidant activity. We demonstrate that the primitive and wild citrus species (e.g., Atalantia buxifolia and C. latipes) have a high level of antioxidant metabolites and are tolerant to various abiotic and biotic stresses compared with cultivated citrus species (e.g., C. sinensis and C. reticulata). Additionally, we highlight the potential usage of citrus wastes (rag, seeds, fruit peels, etc.) and the health-promoting properties of citrus metabolites. Furthermore, we summarize the genes that are involved in the biosynthesis of antioxidant metabolites in different citrus species. We speculate that the genome-engineering technologies should be used to confirm the functions of candidate genes that are responsible for the accumulation of antioxidant metabolites, which will serve as an alternative tool to breed citrus cultivars with increased antioxidant metabolites.

Exogenous Spermine Mitigate Adversities of Salinity Induced Oxidative Stress through Antioxidant Metabolites in Wheat

Change in climatic scenarios due to global warming is characterized by extreme climate variability, land and water degradation which resulted in water scarcity. Accumulation of salts at the surface and sub-surface layers of soils affect crop production of major cereals which is a constraint in sustainable food production. Salinity is a major challenge to tackle wheat cultivation and harness productivity in arid and semi-arid regions of India. In the present investigation, mitigation of salinity induced oxidative stress through exogenous application of spermine (Spm) in four wheat genotypes was studied in relation to antioxidant metabolites. The levels of O2.- increased with increasing levels of salinity in wheat flag leaves. DBW 88 showed the levels of O2.- of 11.75 nmol g-1 FW and 15.74 nmol g-1 FW (at 8 dSm-1 and 12 dSm-1 respectively) at 21 Days After Sowing (DAS) and application of Spm decreased the O2.- content under control and saline stressed conditions at 8 dSm-1 and 12 dSm-1. Hydrogen peroxide content was increased with increasing levels of salinity in all the wheat varieties at 21 DAS. However, the increase was more in the case of DBW 88 when compared with HD 3086. Treatment of Spm decreased the H2O2 content when compared with control and saline stressed wheat varieties. The malondialdehyde (MDA) content was increased with increasing levels of salinity at 21 DAS. The highest increase in MDA content was seen in DBW 88 whereas the lowest increase was found in Kharchia 65. Application of Spm decreased the MDA content under control at both levels of salinity treated wheat varieties. The carotenoid content decreased with increasing levels of salinity in all four wheat varieties. However, the decrease was more in DBW 88 when compared with other varieties viz. HD 3086, Kharchia 65 and KRL 210 at 21 DAS. Exogenous Spm increased the carotenoids content in all four wheat varieties irrespective of the salinity. The leaves of Kharchia 65 and KRL 210 had higher levels of ascorbic acid as compared to that of DBW 88 and HD 3086. Increased content of carotenoid was observed in Spm-treated wheat. Exogenous application of Spm increased the ascorbic acid content in control at both levels of salt stress. The glutathione content increased with an increase in salinity treatment in all the varieties however, a higher increase was observed in Kharchia 65. Exogenous Spm increased the glutathione content in all the varieties irrespective of salinity stress. The results presented in the study indicated that the exogenous application of Spm improved their tolerance levels under salinity.

Responses to Salinity in Four Plantago Species from Tunisia

The genus Plantago is particularly interesting for studying the mechanisms of salt tolerance in plants, as it includes both halophytes and glycophytes, as well as species adapted to xeric environments. In this study, the salt stress responses of two halophytes, P. crassifolia and P. coronopus, were compared with those of two glycophytes, P. ovata and P. afra. Plants obtained by seed germination of the four species, collected in different regions of Tunisia, were subjected to increasing salinity treatments for one month under greenhouse conditions. Morphological traits and biochemical parameters, such as ion accumulation and the leaf contents of photosynthetic pigments, osmolytes, oxidative stress markers and antioxidant metabolites, were measured after the treatments. Salt-induced growth inhibition was more pronounced in P. afra, and only plants subjected to the lowest applied NaCl concentration (200 mM) survived until the end of the treatments. The biochemical responses were different in the two groups of plants; the halophytes accumulated higher Na+ and proline concentrations, whereas MDA levels in their leaves decreased, indicating a lower level of oxidative stress. Overall, the results showed that P. coronopus and P. crassifolia are the most tolerant to salt stress, and P. afra is the most susceptible of the four species. Plantago ovata is also quite resistant, apparently by using specific mechanisms of tolerance that are more efficient than in the halophytes, such as a less pronounced inhibition of photosynthesis, the accumulation of higher levels of Cl− ions in the leaves, or the activation of K+ uptake and transport to the aerial part under high salinity conditions.

Ulva intestinalis Extract Acts as Biostimulant and Modulates Metabolites and Hormone Balance in Basil (Ocimum basilicum L.) and Parsley (Petroselinum crispum L.)

Natural elicitors from macroalgae may affect plant secondary metabolites. Ulvan is a sulfated heteropolysaccharide extracted from green seaweed, acting as both a plant biotic protecting agent, and a plant elicitor, leading to the synthesis of signal molecules. In this work, the aqueous extract of Ulva intestinalis L., mainly composed of ulvan, was used as foliar-spraying treatment and its eliciting effect was investigated in basil (Ocimum basilicum L.) and parsley (Petroselinum crispum L.). Antioxidant metabolites (polyphenols and carotenoids), volatile compounds (both in headspace emissions and hydrodistilled essential oils), and hormones (jasmonic acid, salicylic acid, salicylic acid 2-O-β-D-glucoside, abscisic acid, and azelaic acid) were quantified. The foliar-spraying treatment with U. intestinalis extract increased salicylic acid and its β-glucoside in parsley; in basil, it induced the accumulation of jasmonic and abscisic acids, indicating the presence of a priming effect. In basil, the elicitation caused a change of the essential oil (EO) chemotype from methyl eugenol/eugenol to epi-α-cadinol and increased sesquiterpenes. In parsley EO it caused a significant accumulation of 1,3,8-p-menthatriene, responsible of the typical “parsley-like” smell. In both species, the phenylpropanoids decreased in headspace and EO compositions, while the salicylic acid concentration increased; this could indicate a primarily defensive response to U. intestinalis extract. Due to the evidenced significant biological activity, U. intestinalis extract used as an elicitor may represent a suitable tool to obtain higher amounts of metabolites for optimizing plant flavor metabolites.

Serial Exhaustive Extraction Revealed Antimicrobial and Antioxidant Properties of Platycerium stemaria (Beauv) Desv

Microbial infections are increasing worldwide, and the widespread emergence of antibiotic-resistant pathogens poses a severe threat to public health. Medicinal plants are well-known sources of bioactive ingredients. This study was designed to determine the antimicrobial and antioxidant activities of extracts from Platycerium stemaria. The serial exhaustive extraction method using a solvent of increasing polarity from nonpolar (hexane) to polar (water) was designed to prepare crude extracts; liquid-liquid partition was used to fractionate of active extracts. The extracts and fractions were screened for antimicrobial activity on bacteria and yeasts using the microdilution method. The antioxidant activity was done using DPPH and FRAP assays. Out of the sixteen extracts screened, four (PsHex, PsH2O(H), PsMeOH(EA), and PsMeOH) exhibited potency with minimal inhibitory concentration (MIC) values ranging from 31.25 to 500 μg/mL. Out of the four extracts, two, including PsMeOH and PsMeOH(EA), exhibited DPPH radical scavenging activity with the antiradical power of 8.94 × 10 − 5 and 47.96 × 10 − 5 , respectively, and ferric reducing antioxidant power values ranging from 0.34 to 61.53 μg equivalent Vit C/g of extract. The phytochemical screening of the promising crude extracts revealed flavonoids, glycosides, phenols, tannins, terpenoids, saponins, and anthraquinones. This study reports the antimicrobial and antioxidant activities of P. stemaria for the first time. The results showed that the serial exhaustive extraction approach used in this study allowed capturing the antimicrobial and antioxidant metabolites beyond the single extraction, indicating the need for a rigorous choice of an appropriate solvent and method for extracting P. stemaria. Further investigation is needed to characterize the active ingredients present in the promising extracts.