Factors affecting the leaf extension rate of perennial ryegrass in spring

Abstract

The effects of soil temperature and other factors on the early spring growth of perennial ryegrass (Lolium perenne) swards were studied in 1983, 1984 and 1985. Leaf extension was used as the measure of growth and soil temperature was recorded at 10 cm depth below bare ground. Measurements were taken before the first nitrogen dressing had been applied each spring on swards that had received annual dressings of 0, 200 or 400 kg N ha‐1 since 1982. On the pooled data temperature alone accounted for 604% of the variation in leaf extension rate, with an average increase of 0·4 mm d‐1 for each 1°C increase in temperature over the range studied. Considering the data for each year separately did not greatly improve the correlation but did indicate that leaves extended more rapidly in 1985 for each degree increase in temperature whereas the smallest response was recorded in 1984. A better correlation was achieved by grouping data according to the nitrogen rates previously applied to plots and there was evidence of residual effets of this nitrogen. It seems likely that the differences between years can be explained in terms of differences in radiation and other environmental parameters over the measurement period, whereas the effects of previously applied nitrogen may be more closely related to physiological changes in the sward.

Crescimento de folhas do capim-bermuda tifton 85 submetido à adubação nitrogenada após o corte

“…A temperatura de 15,7 o C pode ter sido limitante para o crescimento das folhas, considerando que a temperatura ótima para a fotossíntese e para a atividade da fosfoenolpiruvato carboxilase em plantas C 4 está entre 30-45 o C e 30-35 o C, respectivamente (Hopkins, 1995). Taxa de expansão da folha associada a variações na temperatura também foi observada por Gastal et al (1992) com festuca e por Baker & Younger (1987) com azevém-perene. Para a aplicação de nitrogênio sete dias após o corte, a expressão do potencial máximo de crescimento das folhas (comprimento e área foliares) ocorreu em doses de nitrogênio mais elevadas (entre 190 a 230 mg kg -1 ) em comparação à aplicação no momento do corte (entre 160 e 180 mg kg -1 ).…”

Características morfogenéticas e taxa de acúmulo de forragem do capim-Mombaça submetido a três intervalos de pastejo

“…Para o azevém foi determinado que a temperatura era responsável por 60,4% da variabilidade na taxa de alongamento foliar (Baker & Younger, 1987 (Medeiros et al, 2002). Cecato et al (1996) observaram que 81% da produção do capim-Mombaça se concentrou no período de maior precipitação e temperatura.…”

Implications of selecting for persistency on hydroponics in timothy (Phleum pratense L.)

“…The obvious phase shift of the temperature in the rooting zone both for soil and hydroponics is expected to change the source/sink ratios on a short term basis. Elevated root temperatures stimulate shoot growth (Baker & Younger, 1987;Kleinendorst & Brouwer, 1972) and increase leaf appearance rates (Davies & Thomas, 1983). The phase shift of temperatures in the soil and in the air will be different in the field and this might be one of the reasons for the discre- Table 1.…”