New Zealand Journal of Crop and Horticultural Science abstracts
Influence of extended photoperiod on photosynthate partitioning
and export in tomato and pepper plants
M. DORAIS
S. YELLE
A. GOSSELIN
Horticulture Research Centre
Department of Plant Science
Laval University
Faculty of Agriculture and Food Sciences
Quebec, Canada G1K 7P4
Abstract Changes in photosynthetic efficiency and carbon
partitioning under extended photoperiods (from 8 to 24 h) was studied using a
photoperiod-sensitive species (tomato--Lycopersicon esculentum Mill.)
and a non-photoperiod-sensitive species (sweet pepper--Capsicum annuum
L.). Extending photoperiod by supplemental lighting resulted in an increase in
total carbohydrates (CH2O) produced in both species. In tomato, extended
photoperiod principally favored shoot development. Dry weight of tomato plants
increased by c. 30% when light periods were increased from 12 to 18 h, although
no significant differences were observed in fruit yields. In contrast, extended
photoperiod did not increase shoot dry weight of pepper plants but
significantly increased its fruit yields. Furthermore, studies on CH2O
translocation supported these data. In pepper plants, translocation efficiency
varied from 71 to 90%, whereas it varied from 54 to 69% in tomato plants. On a
daily basis, tomato plants exposed to extended light periods accumulated more
carbohydrates than pepper plants. Tomato plants had 4.4-4.9 times more
hexoses than sucrose whereas this ratio was only 1.1-1.5 in pepper plants. Such
results lead to the hypothesis that low sucrose phosphate synthase activity in
tomato plants might have resulted in the accumulation of carbohydrates and
phosphorylated intermediates, which in turn decreased inorganic phosphate
levels in the cytoplasm and stroma. This could explain the significant
accumulation of starch in chloroplasts of tomato as well as the absence of
fruit yield increase in plants of this species submitted to extended light
periods.
Keywords Lycopersicon esculentum Mill.;
Capsicum annuum L.; photosynthesis; translocation;
carbohydrates
New Zealand Journal of Crop and Horticultural Science, 1996, Vol. 24:
29-37
0114-0671/96/2401-0029 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (1136K); (scanned from paper original: notes about this process)
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