31 日 緑 工 誌 J. Jap. Soc. 論 文 Reveget. Tech. 23 (3), 161～169 Effect of Salinity on Growth and Ion Concentration in Lolium multiflorum, L. perenne and Festuca arundinacea 塩類が Lolium multiflorum, L. perenne お よび Festuca arundinacea の成長 お よびイオ ン含有率 におよぼす影響 ABDOLZADEH,Ahmad*, SHIMA, Kazuto*, CHIBA, Kyozo** ア ブ ド ウ ル ザ デ イ ・ア ー マ ツ ド*,嶋 一 徹*,千 葉 喬 三** Summary The effect of four levels of salinity (0, 50, 100 and 150 mM NaCl) on growth, Na + accumulation and nitrogen assimilation in three grasses "Lolium multiflorum, Lolium perenne and Festuca arundinacea" was studied. We report a differential response of Lolium and Festuca species to NaCl salinity where Festuca was found to be more resistant than Lolium species. NaCl induced more reduction in dry weight and photosynthetic rate in Lolium species than F. arundinacea. The Na + and Cl- level in plants increased with the increase in salinity. Shoots of Lolium species accumulated high level of Na+ and Cl-. However, high concentration of Na+was not observed in shoots of F. arun- dinacea. Also, the decrease in K+/Na+ ratios were more severe in Lolium species than F. arundinacea. The total-N and NO3- -N concentration decreased drastically in Lolium species due to salinity. However, such an effect was observed only at 150 mM NaCl in F. arundinacea. The NH4+-N concentration was increased in all species under salinity. The results indicate that Na+ exclusion probably rescued the Festuca plant from severe stress while in the Lolium species such a resistance mechanism was not established. Our results suggested that there exists potential to utilize Festuca in pasture land manage- ment in saline areas. 1. Introduction Salt stress represents one of the most serious limiting factors in plant growth and production. Most studies on mechanisms of salt tolerance in terms of salt exclusion and ion concentration in plants has been conducted in crop plants but surprisingly little research has dealt with pasture grasses (Marcar, 1987; Key words : Grass, NaCl stress, Ion concentration in plant キ ー ワ ー ド:草 本 類,ナ ト リウ ム ス トレス,植 物 体 イオ ン含 有 率 * Graduate School of Narural Science and Technology , Okayama University 岡山大学大学院 自然科学研究科 ** Okayama University , Fac. of Agric. Tsushima-naka 岡山大学農学部 ―161― 32 日 本 緑 化 工 学 会 誌 第23巻 第3号(1998) Wu et al., 1994) . Knowledge of the salt tolerant characteristics of pasture grasses may lead to the selection of suitable species for reclamation of saline rangeland. We selected three common grasses of rangeland (Lolium multiflorum, Festuca arundinacea, Lolium perenne) . These species are perennial and sod forming grasses that commonly used for soil protection under wide range of climate. The salt tolerance of these species was evaluated based on Nat exclusion and its role on plant growth. The salt tolerance of many species seems to be associated with the exclusion of Nat and/or Cl- from their shoots and leaves (Tattini et al., 1992; Yan et al., 1992; Fortmeier et al., 1995; Reimann et al., 1995) . On the contrary, it has been reported that the higher NaCl tolerance of tall wheat grass and salt marsh grass compared with L. multiflorum and L. perenne was not associated with lower Nat or higher Kt concentra- tion in shoots (Marcar; 1987) . No reports appear to be available for the salt tolerance of F. arundinacea and the mechanisms involved in salt tolerance of these species. The purpose of the present investigation was to reconsider the role of Nat exclusion in the salt tolerance of Lolium species as compared with Festuca. In this regard we explored the relationship of Na+ exclusion to growth, photosynthetic rate and nitrogen assimilation in the three species. 2. Materials and Methods 2. 1 Plant material and growth conditions Seeds of Festuca arundinacea Shcr. (Tall Fescue) cv. 'Kentuky 31', Lolium multiflorum Lam. (Italian ryegrass) cv. 'Manmos B' and Lolium perenne L. (Perennial ryegrass) cv. 'Friend' were germinated in incubator at 20•}1•Ž A number of 288 seedlings were transplanted to hydroponic solution in green house. Culture solution was made by tap water and contained 5 mM KNO3, 3 mM Ca (NO3)2, 1 mM MgSO4, 1 mM KH2PO4 and micronutrient as described (Gibson; 1987) . The solution was circulated between pots and main boxes and aerated continuously. Treatments including control, 50, 100 and 150 mM NaCl commenced one week after transplanting. The pH of the nutrient solution (6.3•}0.2) was adjusted daily and nutrient solution was changed every week. The averages of daily maximum and minimum of temperature in greenhouse during the growing period were 32 and 14•Ž respectively. Relative humidity was between 54 and 100 percent. Four plants from each species and treatment were randomly harvested weekly. At each harvest, shoots and roots dry weight and ion concentration in the xylem sap were determined. At the end of treatment period, on the fifth week, the plants were sampled for the determina- tion of ions and total carbon and nitrogen concentration. The presented data is related to the fifth week. 2.2 Xylem exudate ion concentration analysis Xylem sap was collected from the decapitated roots that compressed with air in a pressure chamber. The exudated sap was then analyzed for Nat, Me+, NH4+, K+, Ca2+, Cl-, NO3-, SO42- by ion chromato- graphy (HIC-6A Shimazu Co. Kyoto, Japan) . 2.3 Photosynthetic rate assay Net photosynthetic rate were determined weekly using a portable gas-exchange system (ADC Infrared Gas Analyzer type LCA4 with PLC4 chamber, Hertfordshire, England) . 2.4 Growth and mineral analysis The remaining plants were harvested at the end of treatments, separated into shoots and roots and each part was divided into two batches. One batch was dried and ground to powder. The powder from similar species and treatment mixed because they had small volume. The mixed samples analyzed for total nitrogen and carbon concentration using C-N corder (Yanaco Co. Type TNC-600, Kyoto, Japan) . The other batch was subjected to liquid nitrogen extraction and ion chromatographic analysis for the determination of concentration of ions in plant parts. 3. Results 3. 1 Growth The dry weight of shoots and roots decreased with increasing NaCl concentrations in all the three species (Table 1) . The decline in the dry weight due to salinity was more severe in Lolium species than ―162― ABDOLZADEH•ESHIMA•ECHIBA: Effect of salinity on growth and ion concentration in Lolium multzflorum, L. perenne and Festuca arundinacea 33 Table 1 Dry weight of shoots (g plant-1) and roots (g plant-1), shoot root ratio (S/R) and photosynthetic rate (ƒÊ mol CO, m-2 s-1) for three tested species during the fifth weeks. Note: Values of dry weight are means •} SE of six replicate plants. Values of photosynthetic rate are means of five measurements of two plants each. Means within the columns followed by the same letters are not significantly dfferent at P<0.05 by t test. Table 2 Effect of salinity on concentration of Na+ and Cl- (mg g-1 dry weight) in shoots and roots of three tested species at fifth week. Note: Means•} SE (n 6) with different letter are significantly different at P <0.05 by Fisher PLSD test. Concentration of Na+ and Cl- in control culture solution was about 0.40 and 0.26 mM respectively. that of F. arundinacea. In the 100 mM NaCl treatment, the shoot dry weight in L. multiflorum, L. perenne and F. arundinacea decreased to 4, 13 and 61% of controls, respectively. Dry weight of roots decreased significantly at 100 and 150 mM NaC1 in Lolium species and F. arundinacea respectively. The decrease in the shoot/root ratio was not severe in F. arundinacea, but was markedly in 100 and 150 mM NaCl in ―163― 34 日 本 緑 化 工 学 会 誌 第23巻 第3号(1998) Table 3 Concentration of K+ (mg dry weight) and K+/Na+ ratio in shoots and roots of three tested species. Note: Means•}SE (n=6) with different letter are significantly different at P <0.05 by Fisher PLSD test. Table 4 Concentration of NH4-N, NO3- -N and organic-N (mg dry weight) in shoots and roots of three tested species at fifth week. Note: Values of NH4+ -N and NO3- -N are means•}SE of six replicate plants. Organic-N=Total-N-(NH4+ -N +NO3- -N). L. multiflorum, L. perenne respectively. A decrease in a shoot/root ratio in both of Lolium species confirmed the general predominance of the roots during plant growth. 3.2 Photosynthetic rate The photosynthetic rate decreased under salinity in Lolium species (Table 1) . However, at 50 and 100 mM NaCl photosynthetic rate increased slightly in F. arundinacea. In the 150 mM NaCl treatment, photosynthetic rate decreased only by 30% in F. arundinacea but by about 80% in Lolium species, compared with control treatment. The decrease in dry weight and photosynthetic rate due to salinity •\ 64•\ ABDOLZADEH•ESHIMA•ECHIBA: Effect of salinity on growth and ion concentration in Lolium multiflorum, L. perenne and Festuca arundinacea 35 A B C Fig. 1 Effect of NaCl treatments on the composition of Nat, K+, Mg2 , Ca2+ and NH4+-N in xylem sap of L. multiflorum (A), L. perenne (B) and F. arundinacea (C). Note Values are means of four replicate plants. exhibited almost similar trend. 3.3 Na+ and K+ concentration in plants The concentration of Na+ in shoots and roots was negligible in the controls but significantly increased in all species with NaCl treatments (Table 2). Similarly, concentration was increased markedly in treatments. The relationship between the concentration of Na+ and resulted in values of r2 0.82, 0.55 and 0.53 in the shoots of L.