The Physiological Responses of Zea Mays L. and Cucumis Sativus L. on Drought Stress and Re-Watering

Drought leads to deficit water availability and its detrimental effects seriously threaten plant growth. This study assessed the physiological, biochemical, and antioxidant adjustments in different types of photosynthetic plants between Zea mays L. (C4) and Cucumis sativus L. (C3 plant) under response to short-term drought stress. Analyses of relative water content (RWC), proline, and ascorbic acid (AsA) were performed to explore how these plants react to drought. Fifteen-day-old plants were subjected to full irrigation or gradual drought periods for 2-d, 4-d, 6-d, and 8-d following by recovery for 7-d. The results revealed that drought significantly reduces leaf RCW in both plants. Re-watered Z. mays after 8-d drought was higher than C. sativus and reestablished RCW by 23% of stressed plant although remained lower by 9% of the well-watered plant. While, proline and AsA contents in Z. mays were higher than those in C. sativus in drought treatment at 8-d (2.05 µmol/g FW) and 6-d (3174.60 AsA/100 g FW), respectively, that could demonstrate osmotic adjustment ability in this C4 species. The increased proline in both plants also indicates a good strategy for plants to recover. Rewatering gave a decrease AsA and could be expected that plants restore cellular activity after oxidative injury. Based on our study, proline is the most informative biochemical marker to differentiate plant response to drought and Z. mays adjusted defense mechanism to drought rather than C. sativus due to higher accumulation of proline, better antioxidant activity, and improved RCW after recovery.

Insights into the role of cytokinin and gibberellic acid in improving waterlogging tolerance of mung bean

Mung bean (Vigna radiata) is one of the most important pulse crops, well-known for its protein rich seeds, which growth and productivity are severely undermined by waterlogging. In this study, we aim to evaluate how two promising phytohormones, namely cytokinin (CK) and gibberellic acid (GA3), can improve waterlogging tolerance in mung bean by investigating key morphological, physiological, biochemical and yield-related attributes. Our results showed that foliar application of CK and GA3 under 5-days of waterlogged conditions improved mung bean growth and biomass, which was associated to increased levels of photosynthetic rate and pigments. Waterlogged-induced accumulation of reactive oxygen species, and the consequent elevated levels of malondialdehyde, were considerably reduced by CK and GA3 treatments. Mung bean plants sprayed with either CK or GA3 suffered less oxidative stress due to the enhancement of total phenolics and flavonoids levels. Improvement in the contents of proline and total soluble sugars indicating a better osmotic adjustment following CK and GA3 treatments in waterlogged-exposed plants. Most fundamentally, CK or GA3-sprayed waterlogged-stressed mung bean plants demonstrated an increased tendency of the above-mentioned parameters after the 15-day recovery period as compared to water-sprayed waterlogged-exposed plants. Our results also revealed that CK and GA3 treatments increased yield-associated features in waterlogged-stressed plant. Importantly, both phytohormones are efficient in improving mung bean resistance to waterlogging; however, CK was found to be more effective. Overall, our findings suggested that CK or GA3 could be used for the management of waterlogging-induced damage in mung bean, and perhaps in other cash crops.

Anatomical changes in chickpea (Cicer arietinum L.) under aluminium stress condition

An experiment was conducted to investigate the effect of aluminium (Al) toxicity on the anatomical changes in the root, stem and leaf of chickpea (Cicer arietinum L.) plants grown in sand culture. Toxicity of Al reduced the length of primary root and the number of lateral roots of chickpea than that of the control. Aluminium decreased the size and number of vessels in the root of chickpea. Larger area of sclerenchyma cells was noticed in the stem of Al-stressed plant. Number of palisade parenchyma was reduced in the leaf of chickpea. Aluminium treatment caused closure of stomata. Increased number of trichomes in chickpea leaves was also reported due to aluminium. Dhaka Univ. J. Biol. Sci. 30(2): 187-196, 2021 (July)

Viscosity and liquid–liquid phase separation in healthy and stressed plant SOA

Molecular composition, viscosity, and phase state were investigated for secondary organic aerosol derived from synthetic mixtures of volatile organic compounds representing emissions from healthy and aphid-stressed Scots pine trees.

Infra Red Thermography Reveals Transpirational Cooling in Pearl Millet (Pennisetum glaucum) Plants Under Heat Stress

An infra red thermographic analysis of well watered control and well watered heat stressed pearl millet (Pennisetum glaucum) was conducted at ICAR – Central Research Institute for Dryland Agriculture as a part of high resolution phenomics studies to identify the individual quantitative physiological parameters by plant phenotyping that form the basis for more complex abiotic stress tolerant traits. It was seen that the temperature gradient increased gradually from ground level to the top in the control non heat stressed plant. In contrast, it was seen that in the heat stressed plant the temperature increased up to the middle of the plant and then started to decrease at the top of the plant in comparison with the non heat stressed control plant. Our results indicate that the lowering of temperatures in the top of the heat stressed plant may be a mechanism by which the heat stressed plant acclimates to stress by regulating its transpiration thereby bringing in a cooling effect to counter stress.

Isolation, identification, and detection of ACC deaminase gene-encoding rhizobacteria from rhizosphere of stressed pineapple

ACC deaminase is a microbial cytoplasmic enzyme that cleaves ACC, a precursor of ethylene, in the stressed plant. The aims of this study were to isolate, identify, and detect the presence of ACC deaminase gene-encoding rhizobacteria from the rhizospheric soil of pineapple plants that have been exposed to abiotic and biotic stress, specifically herbicide, flooding, and Phytophthora spp. stress. A total of 49 rhizobacterial isolates were obtained, seven of which were observed for their growth on DF medium containing 3 mM L-1 ACC. The four best-growing isolates were selected for genomic DNA extraction. They were molecularly identified as Stenotrophomonas maltophilia (3), Burkholderia territorii (2A), Pseudomonas oryzihabitans (5B), and Bacillus tropicus (1E). A set of primers, 105F-acdS 5’-TGCCAAGCGTGAAGACTGC-3’ and 244R-acdS 5’-GGGTCTGGTTCGACTGGAT-3’, were constructed to amplify the ACC deaminase gene (acdS). Based on melt peak curve analysis, four products appeared to show a specific single peak at 86, 89, 87, and 89.5°C, indicating a single product was produced. In addition, a Blast search showed that these four products met the ACC deaminase feature and their acdS sequences were clustered into an ancestral group compared with the bacterial strains deposited in GenBank. These results suggest that ACC deaminase gene-encoding rhizobacteria from a pineapple plantation of tropical origin may affect the acdS sequences and may contribute to the host plant’s stress tolerance.

Identification of candidate genes involved in the response to different abiotic stresses in potato (Solanum tuberosum L.)

Plants growing in natural habitats are exposed to multiple environmental stresses resulting from abiotic factors such as heat, drought, and cold, which have a significant impact on cultivated potato. We have evaluated in two Solanum tuberosum varieties, Soprano and Kondor, the adaptation to different abiotic stresses as heat, cold, and drought. For this purpose plants of both varieties were stressed, and when they showed symptoms, RNA extraction was carried out and a cDNA library for each sample was constructed. The objective of this study was to detect and analyse the genes involved in the responses to abiotic stresses in potato. The assay generated transcriptome sequences from both varieties, and a total of 5.579.655 reads and 8420 putative candidate genes were generated. 4.027 of the candidate genes were polymorphic and presented a different number of patterns defined by a varying number of SNPs. Many of the generated candidate genes showed differential expression, since the candidate gene was present in the stressed plant, but not in the control plant. The application of this methodology allows us to detect numerous candidate genes or specific alleles/allele combinations, which are differentially expressed in specific samples after the application of different abiotic stresses. This will be useful to identify superior alleles which can be used in Marker Assisted Selection for resistance and tolerance to abiotic stresses.

Detection of Acoustic Emission Characteristics of Plant According to Water Stress Condition

Utilization of acoustic emission (AE) technique for understanding of plant reaction due to the change of environmental conditions was performed in this research. The object of present experiment is to study the acoustic emission characteristics acquired from water-stressed plant and well-watered plant. In this study, two specimens of maize were chosen to be test under controllable environment. The outcomes of this experiment revealed that a large number of AE signals detected from plant were able to be noticed, especially in counts number of AE signals, when the plant was under water stress condition, whereas this situation of AE signals did not appear on plat with well water condition. Moreover, multiple regression calculated to find the correlation between AE parameter received from maize and environmental parameters presented that air temperature was the most important parameter affecting to the RMS value as an AE parameter showing cavitation event of test plant. As these results, AE signals detected from test maize is capable of indicating its water stress condition. Therefore, using of AE method for monitoring the plant is considerably interested as state-of –art technique for increasing productivity, especially in agricultural field.