Regrowth of Genotypes of Tall Fescue Differing in Yield per Tiller1
- Khames M. Zarrough and
- C. J. Nelson2
Tall rescue (Festuca arundinaeea Schreb.) genotypes that have a high yield per tiller also have a low number of tillers/plant arid low residual leaf area after cutting. Our objective was to evaluate the role of stored energy relative to residual leaf area during regrowth of genotypes that differed in yield per tiller. Regrowth following cutting was followed for 6 weeks using genotypes selected for low (LYT), medium (MYT), and high (HYT) per tiller. The pot experiment was conducted outside during late summer and fail 1977, and was repeated in the greenhouse during early spring 1978. Data for the two experiments were similar and so were combined.
When herbage was removed to leave a 5-cm stubble to begin the experiment, number of tillers per pot was double and residual leaf area was nearly six times larger for the LYT genotype than for the HYT genotype. Concentration of water.soluble carbohydrates (WSC) in the stem bases was about 16% of dry weight for the HYT genotype and 10% for the LYT genotype. During the first 2 weeks of regrowth the HYT genotype utilized 235% more WSC per tiller than did the LYT genotype to support a rapid leaf growth rate, which in turn contributed to a greater CO2 exchange rate per pot. Mean crop growth rate , mean net assimilation rate , and mean relative growth rate for the 6-week regrowth period were also greater for the HYT genotype than for the LYT genotype. Relative leaf area growth rate (RLaGR) was initially high for the HYT genotype, then decreased by week 6 to a rate lower than that for the LYT genotype. Ratio of RGR/RLaGR exceeded 1.0 between week 4 and week 5 for the HYT genotype while the other genotypes did not reach the ratio of 1.0 by week 6. In contrast with the LYT and MYT genotypes, the HYT genotype had recovered its original concentration of WSC by week 6.
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