Tolerance In Early Stages Research Articles

Magnetic Field Treatment in Barley: Improved Salt Tolerance in Early Stages of Development

It is known that salinity is one of the most important abiotic stress factors reducing productivity in agriculture. High salt concentration has a negative effect on seed germination and seedling formation. Magnetic field treatment can be considered as an environmentally friendly, innovative and inexpensive method to increase tolerance to stress, as a productivity-enhancing factor in agriculture. In this study, germination rate, germination strength, shoot and root length, fresh and dry weights, chlorophyll a, b and total chlorophyll content and ion leakage values of three different barley varieties under the influence of 150 mT constant magnetic field at different time intervals were determined. In light of the results, it was determined that although it varies according to the barley varieties, it has a significant positive effect on the germination rate and strength depending on the duration of the applied magnetic field. This study revealed that the magnetic field seed treatment has different effects according to the treatment time and the severity of the salt stress.

Increased cell wall thickness of endodermis and protoxylem in Aeluropus littoralis roots under salinity: The role of LAC4 and PER64 genes

Enhanced cell wall lignification is one of the major salinity tolerance strategies in the roots of halophytes. A deep insight into the exact root developmental system in halophytes may be of great importance for understanding plant salt tolerance mechanisms. In this work the developmental and anatomical changes in the roots of halophyte Aeluropus littoralis along with expression patterns of two genes encoding for cell wall laccase (LAC4) and peroxidase (PER64) were investigated. The plants were treated with 0, 300 and 600mM NaCl and root samples were collected 3, 6 and 9days after treatment (DAT). Upon salinity treatment, root diameter and parenchyma thickness were increased significantly in the tip and middle segments compared to upper zones, but the change trend was reversed with the time. It was interestingly revealed that protoxylem was the tissue of target for lignification at root tips, while the highest lignification rates were observed in metaxylem and endodermis in upper segments. Compared to endodermis, protoxylem is restrictively involved in early stages of salt stress in root tips as an efficient barrier against Na+ flow. Gene expression analysis revealed that LAC4 expression was higher in root tips resulting in enhanced protoxylem lignification while PER64 expression was higher in more differentiated zones leading to endodermis thickening. The overall results of this study reveal the crucial role of LAC4 as an important gene in specialized protoxylem lignification in undifferentiated root tips leading to enhanced tolerance in early stages of salt stress.

Heat stress in food legumes: evaluation of membrane thermostability methodology and use of infra-red thermometry

Heat tolerance in 45 chickpea, lentil, and faba bean genotypes was investigated during 2007/2008 and 2008/2009 at Alexandria Agriculture Research Station, Alexandria, Egypt, using screening methods employing the membrane thermostability technique. Threshold temperature to be used in screening for heat tolerance at germination was also investigated for each crop. Temperatures, responsible for 50% germination were 40, 33.5, and 29°C for chickpea, faba bean, and lentil, respectively. Germination percent under high temperature varied significantly (P ≤ 0.05) amongst genotypes. Germination percentage ranged from 4.8 to 71.6, 39.2 to 90.0, and 4.8 to 68.6, in chickpea, lentil, and faba bean, respectively. Differences were significant (P ≤ 0.05) among faba bean and chickpea genotypes. Membrane relative injury (RI%) showed significant (P ≤ 0.05) variability among the genotypes and ranged from 10.57 to 58, 5.2 to 61.7, and 15.7 to 52.7 in chickpea, lentil, and faba bean, respectively. Canopy temperature was measured to evaluate heat avoidance in tested genotypes. Infra-red thermometry was used to measure canopy temperature and the gradient of canopy to ambient air temperature (∆TC-A) in moisture stressed and unstressed treatments. Canopy temperature, leaf water potential (LWP) and leaf water content were affected by the level of soil moisture. Genotypes were able to bring their canopy temperatures to levels lower than ambient air temperatures but the differences were not significant. A heat stress index (HSI) were computed relating the ∆TC-A in moisture stressed to unstressed treatments. Regression of leaf water potential (LWP) and the heat stress index (HSI) was significant (P ≤ 0.05) in faba bean genotypes in the stressful environment. The results of the present investigation emphasize the efficiency of membrane thermostability technique in selection for heat tolerance in early stages of growth in food legumes.

Study of Salinity Tolerance in Rapeseed

Eight diverse Brassica napus genotypes and their 28 F1s were evaluated in nonsaline and saline environments in sand culture. Combined analysis based on two salinity levels revealed significant salinity-level effects for shoot dry weight, plant height, root length, and ions in shoot tissues, including potassium (K), sodium (Na), Ca/Na, and K/Na. Salinity had no significant effect on shoot calcium (Ca) concentration. Stress intensity (SI) estimates, its larger values indicating the more severe stress intensities, were high for all studied traits except for root length, Ca, and Na. The mean of Na in a saline environment was more than seven times the mean in a nonsaline environment, therefore SI was not calculated for this parameter. Low estimates of SI for root length and Ca indicated the effects of a saline environment for these two traits were less than for the other traits. Significant interactions of genotype and salinity levels were observed for all studied traits. The results of factor analysis based on minimum eigenvalue revealed two factors for eight studied traits in a saline environment. Factor one was detected as a nutritional trait in which Ca, K, Ca/Na, and K/Na had a high coefficients factor loading. Factor two was detected as morphological traits. The results of factor analysis indicated that selection for nutritional traits should be more efficient than selection for morphological traits and, specifically, that selection based on K and K/Na should be more efficient than Ca and Ca/Na. Significant positive correlations were found between shoot dry weight and other traits, including Ca, K, Ca/Na, and K/Na in a saline environment; therefore, these ion relations can be used as good selection criteria for improving shoot dry weight. On the basis of low estimates of the tolerance index (TOL) for shoot dry weight (its large value represents more sensitivity to stress), it was concluded that the genotypes including BL2, Ceres, Shiralee, Falcon × BL2, PF7045/91 × Ceres, and BL2 × Ceres had suitable salinity tolerance in early stages of growth.