Environmental effects on leaf structure and tensile strength index in tall fescue (Festuca arundinacea Schreb.)

Synopsis TAKAI, T. and T. YAMADA (2003) : Environmental effects on leaf structure an, d tensile strength index in tall fescue (Festuca arundinacea Schreb.). Grassland Science 49,451-455. The author has already pointed that the evaluation of leaf structure and physical strength would be a valuable selection technique for improving the forage quality in tall fescue (Festuca arundinacea Schreb.). Leaf structure such as the proportion of abaxial bundle sheath extension (ABBSE) and the physical strength such as tensile strength index were measured for plant materials grown in winter, summer and an artificial environment control chamber to clarify the influence of environmental factors on such characteristics. Two tall fescue cultivars, cv. 'Hokuryo' and cv. 'Nanryo', were used in the present study. Plants with a higher or lower ABBSE proportion were selected from each cultivar at Nishinasuno in winter, respectively. These selected plants were then grown in a field at Sapporo in summer and their proportion of ABBSE and tensile strength index were measured. In cv. 'Nanryo', a significant difference between the groups with higher and lower proportions of ABBSE was also observed at Sapporo. The plants of cv. 'Hokuryo', however, showed no significant differences in the level of proportion of ABBSE. This observation suggested that selection for ABBSE proportion in winter could be used to improve the forage quality in cv. 'Nanryo' but not in cv. 'Hokyuro'. Tensile strength index considering leaf width instead of leaf dry weight were measured for plants materials grown in phytotron (day/night temperatures are 24/20 deg C, natural day length) from April to October. Plants having high and low tensile strength index were selected in June, and the proportion of ABBSE was measured for these selected plants in October. In cv. 'Nanryo' plants, the lower tensile strength group showed a significantly lower proportion of ABBSE and sclerenchyma than the higher tensile strength group, but in cv. 'Hokuryo' plants, no significant difference in the proportion of ABBSE and sclerenchyma was observed between two groups. These results suggest that genotypes with non-fall dormancy such as cv. 'Nanryo' could be evaluated in leaf structure and physical strength at any time to improve the forage quality in summer, but genotypes with fall dormancy such as cv. 'Hokuryo' cannot be evaluated from fall to winter, and should be evaluated in spring and summer when they are grown in natural day-length conditions.