Carbon Partitioning in Mature Leaves of Pepper: Effects of Daylength
1985; Oxford University Press; Volume: 36; Issue: 11 Linguagem: Inglês
10.1093/jxb/36.11.1749
ISSN1460-2431
Autores Tópico(s)Plant Stress Responses and Tolerance
ResumoGrange, R. 1. 1985. Carbon partitioning in mature leaves of pepper: effects of daylength.—J. exp. Bot. 36: 1749–1759. The partitioning of recently fixed carbon has been examined in mature pepper leaves grown in 6, 10 or 14 h photoperiods at different irradiances chosen to give similar radiation integrals and in a 6 h photoperiod at the lowest of these irradiances. The partitioning of carbon into export, starch, sugars and respiration was followed over the photopenod and the subsequent night in a mature leaf. The maximum export rate during the day (approximately 18 μg C cm−2 leaf h−1) was not significantly different among the treatments. Net photosynthesis rate was directly related to irradiance; the proportion of net photosynthesis exported during the day was 33% in 6-h days and 57% in 14-h days. Leaf starch accumulation (as a proportion of net photosynthesis rate) increased slightly when plants were grown in 6-h days. The remobilization of starch and sugars at night allowed export rates to remain similar over 24 h when plants were grown in 10-h or 14-h photoperiods. Leaves grown in 6-h days showed no significant changes in export rate during the first few hours of night but exhausted their starch reserves during the night and export rates declined. Sucrose and hexose levels decreased at the onset of darkness, but did not fall below 40 μg cm−2 in plants grown in 10-h or 14-h photoperiods; when this level was reached after 3–4 h of darkness, starch breakdown began. In leaves grown in both 6-h treatments, sucrose levels fell below 40 μg cm−2 when starch reserves were depleted during the night and the export rate decreased concurrently. The results are discussed in relation to the control of export and starch metabolism in the leaf.
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