Journal of Research on Crop Ecophysiology
Volume:9 Issue: 2, Spring 2014

The major constraints of agricultural production in the south western coastal areas of Bangladesh are soil and water salinity of varying degrees, lack of fresh water for irrigation, slow soil drying pattern which are being augmented further due to climate change, requires suitable options of farming systems and component technologies. The major constraints and potentials of agricultural production systems in medium and high saline soils, farmers’ needs and preferences were identified using participatory rural appraisal tools and based on that a number of integrated and component agricultural technologies were listed, validated and identified for scaling out to adapt with the changing climatic situation. The validated technologies were – integrated rice-fish for gher and vegetables on the levee, salt tolerant rice, pulse and oilseed crops and seasonal fruits and vegetables.The integration of salt tolerant high yielding rice varieties and tilapia in ghers with vegetables on the levee increased the gross return (93%) and gross margin (121%) remarkably compared to existing system of cultivating local varieties of rice and mixed species of fishes. The salt tolerant rice varieties, BRRI dhan47 and BRRI dhan53 produced grain yield of 4.00 and 4.65 t ha-1, respectively, in medium saline soils where the popular variety BRRI dhan28 was damaged. Watermelon yielded 3.3 to 5.4 t ha-1 in the fields where soil salinity was recorded 13.8 to 17.3 dS m-1 at maturity in April. Community-based approaches are needed for larger scale dissemination of the validated and identified technologies.

 In order to select the best planting distributions on the rows and study their effects on morphological traits and uptake amount of some nutrients including nitrogen, phosphorus, potassium and calcium in forage of common vetch (Vicia sativa) a factorial experiment was carried out with randomized complete block design and 3 replications in research field of Mohaghegh Ardabili University in Ardabil, Iran. The first factor was the distance between rows including 25, 35 and 50 cm and the second factor was the distance between plants on the rows including 10, 15 and 20 cm. Results demonstrated that the effect of distance between rows was significant on green cover percentage. But the main effects and interaction of distance between rows and between plants on the rows were not significant on traits including number of secondary branches, plant height and plant weight at 10 percent flowering stage. Also, effect of distance between rows and between plants was not significant on fresh forage yield and by decreasing these distances, the yield increased. Mean comparisons demonstrated that planting distributions of 35×20, 35×15 and 50×20 cm increased phosphorus percentage of plants compared to other treatments and the least amount of phosphorus was acquired by planting distribution of 20×20 cm. The effect of planting distribution was not significant on potassium and calcium percentage. Generally, in this experiment the best planting distribution in order to acquire maximum amount of fresh and dry forage in vetch was 20×20 cm, but for the maximum protein content the pattern of 20×50 cm is recommended.

 Evapotranspiration and plant water absorption reduce when exposed to water stress and this reduction results in an increase in leaf temperature. To determine the effect of water stress on leaf temperature and timing of irrigation using leaf temperature, a research was conducted on the Research and Education Greenhouse Production Center of Islamic Azad University, Isfahan Branch (Khorasgan). This study was conducted in controlled conditions and soilless culture of cucumber, tomato, pepper and strawberry. The index of difference between the temperature of air and leaf (ΔT= TAir –TLeaf ) showed leaf temperature which then could indicate the amount of water absorbed by the root therefore, transpiration rates were measured. With an acceptable coefficient of determination model, we concluded that this index (difference between the temperature of air and leaf) was dependent on the intake of water from the roots and leaf transpiration rate, so it can be used as an indicator to determine the time of irrigation.     Abbreviation: VPD: Vapor Pressure Deficit, PAR: Photosynthetically Active Radiation, RH: Relative Humidity, ΔT = TAir –TLeaf.

In order to study the relationships among seed yield and its components in Nigella sativa, path coefficient and factor analysis was done using some agro- morphological traits of 21 different genotypes. Genotypes were evaluated using a completely randomized design with four replications in Ardestan University Research Farms. There was a high and positive correlation between seed yield and biological yield, seed number in follicle, number of stem branches, bush height and harvest index. Stepwise regression analysis for seed yield showed that biological yield, seed number per follicle, number of stem branches and harvest index were entered in the model, respectively, and justified 45 percent of total variation of seed yield. Based on path analysis, biological yield and number of seed in follicle had the highest direct effect on seed yield. Factor analysis revealed 3 hidden factors which totally accounted for 94.12% of variations among traits. These factors were named as efficiency factor (seed yield and biological yield), yield components factor (number of stem branches and follicle number per plant) and follicle trail factor (follicle weight and number of seeds in follicle), respectively. Therefore, the research suggested that biological yield, seed number per follicle and number of stem branches had the most relative effects on seed yield and can be consider as suitable selection criteria for improving seed yield per plant in Nigella sativa.

Aluminum is one of the most important heavy metals which not only can be easily absorbed by roots, but it also damages its normal function and blocks absorption of water and nutrients. According to this fact that sunflower has been widely used in industry, this study investigates the effects of aluminum toxicity on biochemical factors in two sunflower varieties including Sirena (tolerant) and Sanbero (sensitive). The study was carried out in a completely randomized design with aluminum (0, 100, 200, 300, 400, 700 µM) treatments and four replications in hydroponic culture. Experiments are conducted in establishment stage of the plant in four iterations at concentrations of 0, 100, 200, 300, 400, and 700 µm of aluminum. Results of biochemical tests show that aluminum, as a heavy metal, reduces the content of photosynthetic pigments and soluble sugars. In addition, it causes toxicity in sunflower plant. Increase in the proline content of two sunflower varieties show that varieties (Sirena and Sanbero) are more vigorous against oxidative stress with low concentrations of aluminum.

 Crop residues are well known for their chemical (allelopathic) effects on crops. The allelopathic potential of the aqueous extracts and chopped residual of sorghum (Sorghum bicolor L.) on germination, seedling growth, relative water content, seedling dry weight, seedling length and antioxidant enzyme activity namely catalase (CAT), peroxidase (POD) and Superoxide Dismutase (SOD) of Silybum marianum was studied. Petri dish and pot experiments were performed in completely randomized design with three replications. Five concentrations of the aqueous extracts and foliar application of the sorghum [control (water distilled), 5, 10, 15 and 20 w/v] and sorghum chopped (0, 5, 10 and 20 g dry chopped / 100 g soil) were used in the experiments carried out in the laboratory and greenhouse, respectively. Petri dish trial showed that the different extract levels reduced total germination percentage (GP), germination rate (GR) and seedling growth. Moreover, relative water content (RWC), dry weight, and seedling length, antioxidant enzyme activity except CAT of milk thistle bioassay were inhibited when growth in soil incorporated with oven-chopped residual of sorghum. The inhibitory effects often depend on the concentration. Finally, sorghum residues had an enormous potential to suppress elements of germination and seedling growth of milk thistle. Hence, this soil incorporation of allelopathic crop residues could be employed as an important agent for crop rotation management.