Evolution of Morphological and Physiological Response of Agropyron spp. toDrought Stress

Abstract

Introduction: Lack of water resources is one of the most problems ofincreasing urban green spaces. Over the last threedecades, turfgrass and lawn researches have put significant effort into developing and evaluating turf species that have good drought resistance. As water conservation becomes an important issue, considerable interest is increasing in identifying grasses that require less water. Plants with good drought resistance are those that are able to survive stress by means of drought avoidance, drought tolerance at leaf water potentials, or both. The efficient use of water is made possible by understanding the effects of irrigation water on crop development and yield. Drought affects the visual quality, growth rate and evapotranspiration. Researchers reported that turfgrass subjected to drought conditions for short periods could sustain a fairly good appearance by irrigation about half of its consumptive use whenever soil moisture level falls to near permanent wilting point. Drought stress caused decrease in RWC and visual quality of many grass cultivars. In drought conditions resistance grass showed increase in proline content on their leaves. Therefore the use of native grasses with high-strength instead of grass imported with low-resistance is one way to increase green space and reduce costs. The purpose of this study was comparednative grasses with commercial grass cultivars. Materials and Methods: This study was to evaluate the yield and resistance of native grasses to drought stress in 2014. This experiment was conducted in Khorasan Agricultural Research Center. NativeAgropyron grass species includedAgropyronelangatum, A. desertrum, A. cristatum and commercial cultivarwassuper sport and third level of stress, including severe stress (45% FC), moderate stress (65% FC) and control (85% field capacity) were experimental treatments. Plants were cultured in PVC containers measuring 9 cm in diameter and 60 cm deep under greenhouse condition. Soil was mixture of 70% loam soil, 20% pit mass and 10% sand. Greenhouse air temperature was maintained between 22 and 28 centigrade degree. All plants were maintained under well watered conditions for 45 days before drought stress. This experiment was designed in factorial experiment based on completely random with fourreplicates. After the stress treatment parameters such as length and width of leaves, chlorophyll a, chlorophyll b and total chlorophyll content, visual quality, electrolyte leakage, RWC and proline content of leaves were measured. Length and width of leaves were measured with ruler. Proline content, RWC percent, chlorophyll a, chlorophyll b and total chlorophyll content of leaf, visual quality and leaf electrolyte leakage weremeasured with standard protocols. Analysis of the data by statistical software JMP 8 and graphs with Excel 2010 was drawn. Results and Discussion: Result of the experiment showed that those native species have different response to soil moisture stress conditions. The highest and lowest lengths of leaf were observed under45% field capacity in A. elangatum and super sport grass, respectively. The results showed that width of leaves of A. elangatum increase and then decrease in super sport. Under drought stress conditions A. desertrum has best visual quality with 6.07 score. Highest chlorophyll a and total chlorophyll were observed in A. elangatum. The lowest electrolyte leakage under drought stress was obtained from A. elangatum with 17.91 percent. RWC content in the native A. elangatum increased to 82.12 compared with super sport (control). A. elangatum under drought stress showed highest proline content and commercial cultivar (super sport) indicated lowest proline content at 45% field capacity irrigation. Selahvarzi and et al. (2009) found that visual quality of tall fescue decrease in drought stress. In drought stress, RWC percent decrease in grass species. Proline content was increasedupondrought stress inLoliumperenecool season grass. Many studies on native cultivar indicated that native turfgrass cultivar have more resistance to drought stress compared with exotic turfgrass cultivars. Conclusions: According to the results, we said native grass species under drought stress conditions have better quality compared with imported grass cultivar such as Super sport. Visual quality in native grass was suitable for use in urban landscape, that visual quality show little change in drought stress and leaves were fresh in this conditions. The best visual quality of two native species A. elongatum and A. desertrum was observed under 65% field capacity. Nativegrass cultivars were more resistance than imported grass cultivars. This study showed that native grass such asA. elongatum and A. desertrumhas low cost to use and these turfgrass need to lower water irrigation than commercial grass Super sport. Then two species can be introduced as low-input cultivars.

Keywords

• Drought stress
• Electron leakage
• Native grass
• Imported grass
• Proline