Specific Leaf Weight in Zones of Cell Division, Elongation and Maturation in Tall Fescue Leaf Blades

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Abstract
Patterns of change in specific leaf weight (SLW), water-soluble carbohydrate (WSC) content and leaf width were used to delineate the region of secondary cell wall accumulation, and determine the rate of increase in structural material along a developing leaf blade of tall fescue (Festuca arundinacea Schreb.). Structural specific leaf weight (SSLW) was determined by subtracting WSC mass from dry weight to emphasize structural material. Because meristematic activity, cell elongation, and cellular maturation are arranged successively in the grass leaf, these patterns represent a developmental sequence through which each segment of the leaf blade passes. Patterns were generally similar for two genotypes, one selected for high (HYT) and the other for low (LYT) yield per tiller, for a single genotype grown at 17 or 25 °C, and for two field-grown populations which differed in leaf area expansion rate (LAER). In all three studies, the elongation zone of the developing leaf had 31 to 39 per cent WSC on a dry weight basis. The LYT genotype had a higher SLW at all stages of development when grown at 17 than at 25 °C, due to greater WSC accumulation. At 20 °C, the HYT genotype had a higher SLW all along the elongating leaf blade than the LYT genotype. This difference was due to a difference in SSLW, while WSC content was similar. The LER was 64 per cent higher in the high population than the low, but elongation zones were similar in WSC. In all cases, SSLW was high in the meristematic region, lowest near the distal end of the cell elongation zone, then increased linearly as tissue matured. Rate of increase in SSLW was 8.5 and 5.2 g m−2 d−1 for the HYT and LYT genotypes, respectively, and 7.6 and 6.7 g m−2 d−1 for the high and low LAER populations, respectively.