فهرست مطالب a. gazanchian

The Turfgrass industry in saline soil is expanding, making it important to use salinity-tolerant turfgrasses. In this experiment, the effect of salinity stress on some biochemical content in salt-sensitive and salt-tolerant tall fescue was evaluated. The Sanandaj and Daran populations with commercial tall fescue (TF) were evaluated as salt-tolerant tall fescues and the Sanajan population was used as salt-sensitive TF. Five salinity levels of irrigation water (0, 45, 90, 135, and 180 mM NaCl) were applied to turfgrasses to identify the tolerance mechanisms in tolerant tall fescue under salinity stress. Results showed that salinity affected all turfgrasses in proline, chlorophyll, 1-1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, as well as sodium and potassium in their shoots. Sanajan population in 90, 135, and 180 mM salinity had the lowest chlorophyll content among all turfgrasses. Salt stress leads to an increase in the activity of proline compared to the control at the first stage (for evaluating osmotic stress) of measurement. In the second stage (to evaluate ionic stress), at concentrations of 135 and 180 mM NaCl, maximum proline was recorded in Daran and Sanandaj populations, respectively. The interaction effect of salinity and TF was significant for DPPH activity. The Na+/ K+ ratio in the Sanajan population was the highest at all salinity levels. In conclusion, the growth and antioxidant capacity of Festuca arundinaceae populations differ in their response to NaCl treatments. In salt-tolerant TF, proline and antioxidant activity increased with increasing NaCl. These may be a mechanism to protect tolerant TF in salt stress, leading to lower accumulated Na+ in tolerant TF, high K+ uptake, and high chlorophyll content. Based on these results, proline content, DPPH radical scavenging activity, chlorophyll contents, and potassium content could use to distinguish tolerant TF from sensitive TF.

Turfgrasses, as one of the important components of urban landscapes, have played a vital role in this regard. However, the main problems of turfgrass development are the cost of turfgrass seeds, maintenance costs such as moving, as well as the high water requirement in arid and semi-arid regions. Thus, the reduction of lawn culture in the landscape is one of the decision has taken in parks and green spaces organization of Tehran, Isfahan and even Mashhad. For over ten years, researchers have been looking for alternatives to conventional grass lawns to reduce the high cost of maintenance especially irrigation cost in urban landscapes. According to many researches, one of the potential ground cover alternatives that might be used instead of turfgrass is White Clover. Clover (Trifolium spp.) from Fabaceae family is a genus of about 300 species.

The aim of this experiment was to compare three common turfgrasses with two clover varieties as turf replacement to reduce landscape maintenance cost specially moving cost. So, some growth and qualitative factors of clover lawn: Trifolium repens var. Calway and Trifolium repens var. Pipolina (micro clover) and three turfgrasses of Festuca arundinacea L. and Lolium perenne L. and commercial sport turf mixture (from NAk-Nederland Ltd.) were compared together. This research was conducted in randomized complete block design with three replications in the research field of the Department of Horticultural Science and Landscape Engineering‚ Faculty of Agricultural‚ Ferdowsi University of Mashhad‚ Mashhad‚ Iran, during 2016 and 2017. The site (59º 38′ E and 36º 16 ′ N; elevation 989 m) is located in an arid and semi- arid region with mean annual rainfall 233.8 mm and long term averages of maximum and minimum temperature are 22.5 ºC and 9.3 ºC‚ respectively. Turfgrass plots were established by directly sowing the seeds in April, 2016. The planting rate of the seedling considering their pure live seeds (PLS) were 45 g.m-2 for Lolium perenne, 34 g.m-2 for Festuca arundinacea, 6.5 g.m-2 for Trifolium repens, 5.5 g.m-2 for micro clover and 39 g.m-2 for commercial mixture of sport turf. The plots were 1 m2 (1m×1m) in size and were prepared after plowing and leveling the soil. The seeds were hand sown and covered with a thin layer of leaf compost and sand.

According to the results in the first evaluation of emergence percentage, Lolium perenne had the highest emergence percentage. After 36 days from culture, all plants had 92-98 % coverage which did not have any significant difference among grasses with clover lawns. In terms of density, uniformity and weed density, there was no significant difference between the studied plants. In the other hands, white clover showed the best quality after clipping in both years. At the point of growth index, which have done in this experiment by measuring height and dry weight of clipping, grass lawns had the higher growth index in compered to clover lawn in both years. Festuca arundinacea and Lolium perenne had the highest growth index and white and micro clover had the lowest growth. Also, with air warming, Festuca arundinacea became dominated plant in height and clipping dry weight. In July, Festuca arundinacea produced the highest clipping dry weight by 40 gr.m-2, Lolium perenne (19.52), commercial sport turf (15.68), white clover (6.24) and micro clover (0.36) gr.m-2.

One of the problems of landscape is reduction of maintenance costs such as mowing. So, the low growth of white and micro clover is a positive factor in reduction of the moving costs than turfgrasses. Also, the coverage and proper density of clover lawns are similar to grass lawns and did not have a significant difference with them. The character of low growth can be effective in reduction of irrigation costs in white and micro clover, which requires more research and examination in future. This is a positive point in the white clover and micro clover that do not need to move or cut every months. Almost, clover moving is recommended for removing their flower. Therefore, it is recommended to use white and micro clover as a replacement with less maintenance costs in landscape. Finally, the results of cultivation of grass and clover as monoculture in this study can be used to produce clover-grass mixtures suitable for the climate of our country (arid and semi-arid regions), instead of importing turf mixtures from European countries.

Many uses of landscape and important roll of ground covers aspect turfgrasses caused extensive of this plant in the cities. This study focuses on shoot responses and tolerance of native and commercial turf grasses under drought stress in a factorial experiment based on unbalanced completely random design on the year 2006. The specious that we used in this experiment included (i) commercial tall fescue (Festuca arundinacea) (ii) commercial perennial ryegrass (Lolium perenne) (iii) native tall fescue population (Festuca arundinacea). The drought stress levels included (i) 50%FC (ii) 25% FC (iii) recovery from drought stress and 3 groups of pots that was always in the field capacity condition. The results of this study showed that dry weight decreased 26.4% in 25% FC traits in compare with control traits under severe drought stress. Decreased in leaf wide, leaf total area, leaf total length and increase in leaf diameter caused decrease in evaportanspiration under drought stress in festuca genus. Parameter of quality change (TQ) and decrease in total chlorophyll content was minimum in native tall fescue and maximum in commercial ryegrass, from perfect irrigation to sever drought stress. Shoot dry weight, leaf width, total leaf area and total leaf length, visual quality and leaf total chlorophyll content increased 18.2%, 103.3%, 74.4%, 28.8%, 64.1%, 40.8% respectively, and mean leaf diameter decreased 53.2% in compare with sever drought stress condition after 14 days rewatering.

The lack of water is the most important problem in extensive landscape especially turfgrass in arid and semi arid regions. The root responses in native and commercial grasses under drought stress were investigated. This experiment was in a factorial experiment based on unbalanced completely random design on the year 2006. The specious that we used in this experiment included (i) commercial tall fescue (Festuca arundinacea) (ii) commercial perennial ryegrass (Lolium perenne) (iii) native tall fescue population (Festuca arundinacea). The drought stress levels included (i) 50%FC (ii) 25% FC (iii) recovery from drought stress and 3 groups of pots that was always in the field capacity condition. The replicates for control pots and drought/recovery treatments were 3 and 4 respectively. The results showed that root dry weigh of commercial and native tall fescue increased 40%, 11.9% respectively compared with control under severe drought stress. Whereas it decrease 33.6% in lolium perenne compared with control at same condition. Another root traits such as volume, total area and root total length in the native tall fescue increase 60.1%, 34.6%, 70.1% respectively compared with control under severe drought stress. This traits in plus 54% decrease in root diameter caused increased in rank of absorption and depletion of water from dry soil. That it caused better yield of this grass under drought stress. Ability of recovery in most morphological root characters increase in commercial grass after rewatering in compare with severe drought stress condition.