Journal of Plant Ecophysiology
Volume:2 Issue: 2, 2010

To evaluate the effect of drought stress on the variation of leaf water potential, relative water content and SPAD in two plantago species (Plantago ovata and P. psyllium) as well as the improvement rate of these parameters after re-irrigation, an experiment was conducted at Agriculture Research Center, Melbourne University, Australia in 2006. Leaf water potential was constant within five days after irrigation stop and afterwards, it decreased to -1.6 and -2.0 MPa for P. psyllium and P. ovata at eighth day and -2.3 and -2.8 MPa at tenth day, respectively. Relative water content of both species was 90% up to two days after irrigation stop and had no significant difference with control treatment, but as stress intensified, relative water content of both species significantly decreased. With the decrease in relative water content and further decrease in leaf water potential, SPAD increased in both species, so that leaf chlorophyll content was 17 and 37% in P. ovata and P. Psyllium at relative water content of 60% and/or leaf water potential of -1.5 MPa, respectively.

Hydroponically integrated fish and plant production system (aquaponics) is a new production method that has received attention by growers and researchers recently. In order to investigate the effect of different plant substrates (perlite/cocopeat ratios) on strawberry growth and development in hydroponic and aquaponic systems, a greenhouse experiment was carried out as a factorial trial with a completely randomized design in three replications. Results of statistical analysis showed that in hydroponic system, leaf, crown and root fresh weight, runner length, individual leaf weight, chlorophyll a and b content (in high cocopeat ratios), total chlorophyll and carotenoid content (in high cocopeat ratios), were significantly higher than aquaponic system. Increase of cocopeat to perlite ratio in hydroponic system caused a higher chlorophyll a and b content in leaves and this increase was accompanied with increase of plant growth. Results of this research revealed that most of the measured features were better in hydroponic system than in aquaponic system. In addition, the perlite or cocopeat substrates individually were not appropriate for cultivation but their combination was found to be suitable as substrate for cultivation.

Soil salinity may reduce potassium (K) uptake due to strong competition with sodium cations in the root regions. In calcareous soils, zinc (Zn) precipitates in unavailable forms for plants. In this study, the response of two wheat genotypes (C) named Backcrossroshan and salinity tolerant Line No.4 was studied against to K and Zn fertilizers. A factorial experiment with four levels of K (K0=0, K1=60, K2=120 and K3=180 kg ha-1) and three levels of Zn (Zn0=0, Zn1=20 and Zn2=40 kg ha-1) based on a randomized complete block design was employed. Results of analysis of variance showed significant Zn×K×C interactions for all the measured traits except for ear length. Despite of illite clay and enough available potassium in the root growing media, plants responded to K application. Yield components, grain yield and protein content of the two genotypes increased linearly as the levels of K×Zn interaction treatments increased. Considering K2Zn2 and K3Zn2 treatments, Line No.4 produced 1000-grain weight, weight of grains per ear and grain yield higher than Backcrossroshan by 17%, 30%, and 23%, respectively. Results showed significant relationship between grains weight per ear and grain yield. Consequently the higher the grain weight per spike the higher grain yield was obtained. Results achieved highlight the importance of K and Zn nutrition in salt stress conditions.

Salicylic acid (SA) is an important signal molecule modulating plant response to stress. A field trial was, therefore conducted to study the impact of salicylic acid (SA) at 0, 0.1 and 0.5 mM on growth and biochemical parameters, bulb yield and allicin contents in a local garlic cultivar under drought stress in Iran. Drought significantly reduced all parameters recorded but allicin percentage. Whole plant fresh weight and bulb yield as the two economically important traits were reduced by 37% and 28%, respectively under drought stress conditions. On the contrary, SA increased root fresh and dry weights, bulb length, clove (length, number, brix and allicin percentage), harvest index and allicin percentage and the effect of 0.5 mM SA was more pronounced. The interaction of SA and drought was significant for most parameters recorded and in most cases SA was more effective under drought stress than non-stress conditions. Relative to the corresponding control, 0.5 mM SA increased bulb yield by 49% under drought stress and 24% under non stress conditions. This effect was even more pronounced for allicin content and the relative increases under stress and non stress conditions were 67% and 40%, respectively.

Identifying and assessing genetic diversity has a significant impact on cotton improvement programs. For this purpose, electrophoresis of seed storage proteins is a beneficial tool for identification of genetic diversity and genetic distance among cultivars. In this research, water and salt soluble proteins were extracted from cotton seed and after the electrophoresis, scoring and analysis was done. The results showed that there were 16 bands for 18 cultivars. The highest number of bands belonged to Avangard, 010 and B-557 cultivars and the lowest to Oltan. UPGMA cluster analysis was carried out using the coefficient of Jaggard, and the results revealed five genetic groups. Principal Coordinates analysis showed that the first three principal components explained 81.31 percent of total variance of the data. Also, according to the information obtained from Nei's (1973) gene diversity, 14 markers were polymorph and two markers were monomorph. Therefore, presence of genetic diversity as evaluated by seed storage proteins will make it possible to use these markers in different breeding programs.

In order to evaluate yield and yield components of four lentil genotypes (local line, local landrace, ILL-10314 and ILL-6037) as affected by three N fertilizer levels as urea (0, 45, 90 kg/ha), an experiment was conducted at Ardabil Agriculture Research Station, Iran in 2008 as a factorial one based on randomized complete block design with three replications. According to the results, different N fertilizer levels did not have any significant effects on the studied traits, while genotype significantly affected all the studied traits. Having the highest filled pod number and grain number/plant, the local line produced the highest grain yield. In spite of having high grain number/plant, grain number/pod and filled pod number, ILL-10314 had the lowest grain yield, 23% lower than grain yield of local line, which could be partly related to its lower 100-grain weight (about 80% lower than the highest 100-grain weight). ILL-6037 had the lowest filled pod number. This genotype stood in a same yield group as the local line and landrace because of having the highest 100-grain weight.

Salinity is a major constraint in agricultural lands reducing growth and productivity of crops. Salicylic acid (SA) as a plant hormone is known to alleviate the adverse effects of many stresses including salinity. Therefore, in a series of experiments the effect of pre-sowing seed soaking with SA (0, 0.1 and 0.5 mM) on seed germination and seedling growth under NaCl (0, 150 and 200 mM) was studied in two contrasting wheat cultivars; Roshan (intolerant) and Mahdavi (tolerant). Salinity reduced germination percentage (GP), germination rate (GR) and vigor index (VI) in both cultivars and the effect of 200 mM was more severe. On the contrary, SA improved GP in both cultivars and VI in Roshan. Salinity reduced shoot growth, K+ uptake and K+/Na+ ratio and increased Na+ uptake and electrolyte leakage (EL) in leaf tissues of both cultivars. On the other hand, SA increased shoot dry weight (SDW), root dry weight (RDW) and K+ uptake and decreased Na+ content in shoots of cultivars and the effect of 0.5 mM was more pronounced. SA was effective in improving shoot length (SL) and EL only under salt stress conditions whereas shoot and root dry weight were improved under both stress and non-stress conditions. It is concluded that seed treatment with SA may promote germination and subsequent seedling growth of wheat cultivars under salinity conditions via maintaining cellular membrane integrity and reducing Na+ in favor of K+ accumulation in shoot.

The growing expansion of world population as well as the development of agricultural and industrial activities for supplying food on one hand and the recent frequent droughts on the other hand has maximized the utilization of surface fresh water resources in most countries on arid belt and therefore they are under an excessive pressure. One major solution to fight water crisis is the chain usage of water according to its quality in different sections and optimum usage of unconventional waters in agriculture. Therefore, the current study was carried out to examine the effects of irrigation with urban sewage on yield and yield components of sweet pepper in Sewage Treatment Station of Bahonar University of Kerman, Iran in 2007. The experiment was a randomized complete block design with four replications and five treatments (urban sewage with concentrations of 0, 25, 50, 75 and 100%). The results showed that application of treated sewage as irrigation water significantly increased chlorophyll, plant height, fruit fresh and dry weight, fruit number and shoot and root dry weight compared with control. The greatest increase happened in sewage concentration of 100%. The treatments did not show significant difference with control regarding Mn concentration of sweet pepper plants, while as sewage percentage increased, the concentrations of N, P, Fe and Na significantly increased. Hence, the sewage can be used in irrigating sweet pepper. However, it should be noted that the quality and characteristics of sewage varies with place and even with time in a given place. Thus, sewage application in irrigation must be in sound managerial framework under constant control on the basis of water, soil, plant and environment characteristics of a given place.