Study of Genetic Analysis of Physiological Attributes under Normal and Drought Conditions in Gossypium hirsutum L.

The aim of this study was to identify the suprior cotton genotypes with improved physiological characteristics under drought conditions. On the bais of root-shoot charcteristics, five genoypes of G. hirsutum were identified as drought tolerant and three genotypes screened out as drought susceptible. The field screening experiment were carried out to validate the findigs of root-shoot screening sudy on the basis of physiological as well as agronomical chracteristics. Both drought tolerant and susceptible genotypes were grown in glass house in pots and followed line x tester mating desighn to cross these genotyps. Parents with their fiftenn offsprings were grown in field conditions in very next cotton season for further analysis. Analysis of variance showed the existence of significant variations among the accessions for all the physiological parameters i.e, osmotic potential, relative water content, cell injury, leaf water potential, excised leaf water loss, stomatal conductance, photosynthesis rate and transpiration rate. Further, among parents line, MS-64 and tester, BH-176 showed superior performance under water scarce conditions. Among the crosses COOKER-315 x Cyto-62 and GS-444 x MPS-11 were better perfomed for high yielding parametrs. The results showed that these two combinations might be helpful to develop drought resistant germplasm on large scale.

The Enhancement of Drought Tolerance in Arabidopsis Plants Induced by Pretreatment with Sulfur Dioxide

Sulfur dioxide (SO2) is a common air pollutant that has multiple effects on plants. Here, the effect of prior exposure to SO2 on the improvements of drought tolerance and possible regulation mechanisms were investigated in Arabidopsis plants. The experimental results showed that pre-exposure to 30 mg/m3 SO2 for 72 h could reduce leaf water loss, and enhance the drought tolerance of Arabidopsis plants. SO2 pre-exposure decreased leaf stomatal conductance (Gs) and transpiration rate (Tr) but increased net photosynthetic rate (Pn), water use efficiency (iWUE) and photosynthetic pigment contents under drought conditions. Importantly, the activities of superoxide dismutase (SOD) and peroxidase (POD) were significantly increased, while the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were decreased in SO2-pretreated Arabidopsis plants under drought stress. Additionally, the activity of o-acetylserine(thio)lyase (OASTL) and the content of cysteine (Cys), the rate-limiting enzyme and the first organic product of sulfur assimilation, were increased significantly in drought-stressed plants after SO2 pretreatment, along with the increases of other thiol-containing compounds glutathione (GSH) and non-protein thiol (NPT). Meanwhile, SO2 pre-exposure induced a higher level of proline accumulation, accompanied by the increased activity of proline synthase P5CS, the decreased activity of proline dehydrogenase ProDH and the corresponding alteration of gene transcription. Collectively, the enhanced drought tolerance afforded by SO2 might be related to the improvement of plant photosynthesis, antioxidant defense, sulfur assimilation and osmotic adjustment. These findings provide new insights in understanding the role of SO2 in plant adaptation to environmental stress.

Response of wheat varieties to salinity: growth, yield and ion analysis

In plants, development, growth and yield most severely affected through saline soil/water in growth medium, ultimately cause severe threat to global food production for human being. Wheat (Triticum aestivum) is the most edible crop in Pakistan. Production of this crop can be improved through using marginal areas with the help of growing salt-tolerant varieties. The present investigation is carried out to screen out six local wheat varieties (F.Sarhad, Insaf, Lalma, Tatora, Bathoor and Barsat) with reference to their vegetative and reproductive growth, different physiological parameters [relative water content (RWC), electrolyte-leakage (EL) and leaf water loss (LWL)] and ionic status of plants. Present experiment designed in completely randomized manner (CRD) and 54 pots were arranged in the Botanical Garden, Department of Botany. These pots arranged in 6 lines with 9 pots/line and each line was irrigated with non-saline (control), 50 mM and 150 mM NaCl solution. The data from present research revealed that application of salt cause significant reduction in plant-height, root-length, fresh-biomass, dry-biomass, seed number/plant, seed weight/plant, spike-weight, relative water content, leaf water loss, and different ions of plants. Similarly at same applied doses of salt weight of 100 seeds, spike-length, electrolyte-leakage, Na+ and Cl- ions become increased. It has been concluded from the results of present study that varieties F. Sarhad, Insaf and Lalma exhibited more salt tolerance as compare to other varieties. So, these recommended for growing on moderately salt affected soil/water to achieve more yield of wheat from such affected lands of Khyber Pakhtunkhwa, Pakistan.

Unraveling the Strategies Used by the Underexploited Amaranth Species to Confront Salt Stress: Similarities and Differences With Quinoa Species

Yield losses due to cultivation in saline soils is a common problem all over the world as most crop plants are glycophytes and, hence, susceptible to salt stress. The use of halophytic crops could be an interesting alternative to cope with this issue. The Amaranthaceae family comprises by far the highest proportion of salt-tolerant halophytic species. Amaranth and quinoa belong to this family, and their seeds used as pseudo-cereal grains have received much attention in recent years because of their exceptional nutritional value. While advances in the knowledge of salt tolerance mechanisms of quinoa have been remarkable in recent years, much less attention was received by amaranth, despite evidences pointing to amaranth as a promising species to be grown under salinity. In order to advance in the understanding of strategies used by amaranth to confront salt stress, we studied the comparative responses of amaranth and quinoa to salinity (100 mM NaCl) at the physiological, anatomical, and molecular levels. Amaranth was able to exhibit salt tolerance throughout its life cycle, since grain production was not affected by the saline conditions applied. The high salt tolerance of amaranth is associated with a low basal stomatal conductance due to a low number of stomata (stomatal density) and degree of stomata aperture (in adaxial surface) of leaves, which contributes to avoid leaf water loss under salt stress in a more efficient way than in quinoa. With respect to Na+ homeostasis, amaranth showed a pattern of Na+ distribution throughout the plant similar to glycophytes, with the highest accumulation found in the roots, followed by the stem and the lowest one detected in the leaves. Contrarily, quinoa exhibited a Na+ includer character with the highest accumulation detected in the shoots. Expression levels of main genes involved in Na+ homeostasis (SOS1, HKT1s, and NHX1) showed different patterns between amaranth and quinoa, with a marked higher basal expression in amaranth roots. These results highlight the important differences in the physiological and molecular responses of amaranth and quinoa when confronted with salinity.

Smart Glass Impacts Stomatal Sensitivity of Greenhouse Capsicum Through Altered Light

Optical films that alter light transmittance may reduce energy consumption in high-tech greenhouses, but their impact on crop physiology remains unclear. We compared the stomatal responses of Capsicum plants grown hydroponically under control glass (70% diffuse light) or smart glass (SG) film ULR-80, which blocked >50% of short-wave radiation and ~9% of photosynthetically active radiation (PAR). SG had no significant effects on steady-state (gs) or maximal (gmax) stomatal conductance. In contrast, SG reduced stomatal pore size and sensitivity to exogenous ABA thereby increasing rates of leaf water loss, guard cell K + and Cl - efflux, and Ca 2+ influx. SG induced faster stomatal closing and opening rates on transition between low (100 µmol m -2 s -1) and high PAR (1500 µmol m -2 s -1), which compromised water use efficiency relative to control plants. The fraction of blue light (0% or 10%) did not affect gs in either treatment. Increased expression of stomatal closure and photoreceptor genes in epidermal peels of SG plants is consistent with fast stomatal responses to light changes. In conclusion, stomatal responses of Capsicum to SG were more affected by changes in light intensity than spectral quality, and re-engineering of the SG should maximize PAR transmission, and hence CO2 assimilation.

Silicon attenuates calcium deficiency by increasing ascorbic acid content, growth and quality of cabbage leaves

Calcium (Ca) deficiency in cabbage plants induces oxidative damage, hampering growth and decreasing quality, however, it is hypothesized that silicon (Si) added to the nutrient solution may alleviate crop losses. Therefore, this study aims at evaluating whether silicon supplied in the nutrient solution reduces, in fact, the calcium deficiency effects on cabbage plants. In a greenhouse, cabbage plants were grown using nutrient solutions with Ca sufficiency and Ca deficiency (5 mM) without and with added silicon (2.5 mM), arranged as a 2 × 2 factorial in randomized blocks, with five replications. At 91 days after transplanting, the plants were harvested for biological evaluations. In the treatment without added Si, Ca deficiency promoted oxidative stress, low antioxidant content, decreased dry matter, and lower quality leaf. On the other hand, added Si attenuated Ca deficiency in cabbage by decreasing cell extravasation while increasing both ascorbic acid content and fresh and dry matter, providing firmer leaves due to diminished leaf water loss after harvesting. We highlighted the agronomic importance of Si added to the nutrient solution, especially in crops at risk of Ca deficiency.

Investigation on the effects of water loss on the solar spectrum reflectance and transmittance of Osmanthus fragrans leaves based on optical experiment and PROSPECT model

In addition to reducing water content, leaf water loss also exerted three effects on the leaf reflectance and leaf transmittance, i.e., the increases of brown pigment content, leaf refractive index, and leaf internal structure index.

Dissecting the Roles of Cuticular Wax in Plant Resistance to Shoot Dehydration and Low-Temperature Stress in Arabidopsis

Cuticular waxes are a mixture of hydrophobic very-long-chain fatty acids and their derivatives accumulated in the plant cuticle. Most studies define the role of cuticular wax largely based on reducing non-stomatal water loss. The present study investigated the role of cuticular wax in reducing both low-temperature and dehydration stress in plants using Arabidopsis thaliana mutants and transgenic genotypes altered in the formation of cuticular wax. cer3-6, a known Arabidopsis wax-deficient mutant (with distinct reduction in aldehydes, n-alkanes, secondary n-alcohols, and ketones compared to wild type (WT)), was most sensitive to water loss; while dewax, a known wax overproducer (greater alkanes and ketones compared to WT), was more resistant to dehydration compared to WT. Furthermore, cold-acclimated cer3-6 froze at warmer temperatures, while cold-acclimated dewax displayed freezing exotherms at colder temperatures compared to WT. GC-MS analysis identified a characteristic decrease in the accumulation of certain waxes (e.g. alkanes, alcohols) in Arabidopsis cuticles under cold acclimation, which was additionally reduced in cer3-6. Conversely, the dewax mutant showed a greater ability to accumulate waxes under cold acclimation. FTIR spectroscopy also supported observations in cuticular wax deposition under cold acclimation. Our data indicate cuticular alkane waxes along with alcohols and fatty acids can facilitate avoidance of both ice formation and leaf water loss under dehydration stress, and are promising genetic targets of interest.

Evaluation of different cotton varieties against drought tolerance: A comparative analysis

The limited water supply for irrigation is a major constraint to cotton production. Morphological and physiological traits provide useful information for drought tolerance. This research work was carried out for the identification of cotton genotypes having better drought tolerance. For this purpose, forty (40) genotypes of upland cotton were studied under two moisture regime, i.e. normal and drought environment in field conditions. The experiment was conducted using split plot design under RCBD arrangement. All the genotypes behaved differently under two moisture levels. The interaction of cotton genotypes with two moisture levels were studied for various traits, i.e. plant height, sympodial branches, seed cotton yield, boll weight, number of bolls per plant, excised leaf water loss and relative water content by using Principle Component Analysis (PCA). Results showed that the genotypes VH-144, IUB-212, MNH-886, VH-295, IR-3701, AA-802, NIAB-111, NS-121, FH-113, and FH-142 are either stable or showing positive interaction with drought conditions for most of the traits under studied. These genotypes can be used in further breeding program for developing varieties suitable for cultivation under drought conditions, whereas; IR-3, CIM-443, FH-1000, MNH-147, S-12 interacted undesirably with drought stress

Arabidopsis CK2 family gene CKB3 involved in abscisic acid signaling

CKB3 is a regulatory (beta) subunit of CK2. In this study Arabidopsis thaliana homozygous T-DNA mutant ckb3 was studied to understand the role of CKB3 in abscisic acid (ABA) signaling. The results shown: CKB3 was expressed in all organs and the highest expression in the seeds, followed by the root. During seed germination and root growth the ckb3 mutant showed reduced sensitivity to ABA. The ckb3 mutant had more stomatal opening and increased proline accumulation and leaf water loss. The expression levels of number of genes in the ABA regulatory network had changed. This study demonstrates that CKB3 is an ABA signaling-related gene and may play a positive role in ABA signaling.