Subtropical grass growth. 1. Relationship between carbohydrate accumulation and leaf area in growth

Abstract

Green panic and buffel grass were cut at a height of 5 cm either once or 8 times per year. Green panic produced more stem above 5 cm than buffel grass and substantially less root material. Frequent defoliation reduced fluctuations in shoot growth, enhanced leaf growth and tillering and reduced stem-, inflorescence-and root growth. Non-structural carbohydrate (TAC) accumulated in the roots during autumn, winter and early summer and was depleted in the spring. Buffel grass had a higher concentration and total content of TAC than green panic. Frequent defoliation reduced the amount of TAC. In a further study with green panic, leaf area remaining after defoliation was more important in determing growth rate than was TAC status. NAR varied markedly as a result of treatment, but photosynthetic capacity had more influence on growth. In a subsidiary comparison, there were indications that under conditions of carbohydrate starvation, compounds other than TAC were involved in respiration and shoot synthesis. In neither experiment were TAC levels simply related to shoot growth after defoliation.-A.M.H.