Photosynthesis in response to sink-source activity and in relation to end products and activities of metabolic enzymes in peach trees.
Fruits were removed (-fruit) or retained (+fruit) on limbs of 'Yanfengyihao' peach (Prunus persica (L.) Batch) trees. In addition to the -fruit and +fruit treatments, leaves on 1-year-old fruit-bearing shoots of 'Bayuecui' peach trees were covered with bags for varying periods of time. Net photosynthetic rate (P(n)), stomatal conductance and transpiration rate around midday significantly decreased in the -fruit treatment and significantly increased in bagged leaves after removal of the bags compared with values in the +fruit treatment. Leaf temperature (T(l)) was higher in the -fruit treatment than in the +fruit treatment, and P(n) decreased in the -fruit treatment, especially when T(l) exceeded 38 and 36 degrees C in 'Yanfengyihao' and 'Bayuecui', respectively. Fruit removal resulted in a significant accumulation of sorbitol and starch in leaves, but it did not decrease activities of enzymes involved in carbon metabolism in leaves of 'Yanfengyihao'. In contrast, activities of aldose-6-phosphate reductase and ADP-glucose pyrophosphorylase sometimes increased in leaves in the -fruit treatment. In 'Bayuecui', fruit removal significantly decreased maximal fluorescence and photochemical efficiency and increased minimal fluorescence around midday compared with values in the +fruit and bag treatments. The photosynthetic apparatus of peach may be damaged when T(l) exceeds a critical temperature under conditions of decreased sink demand. Decreased stomatal aperture and increased T(l) may regulate photosynthesis by affecting electron transport.
Li
Wei D
WD
Institute of Botany, The Chinese Academy of Sciences, 100093 Beijing, P.R. China.
Duan
Wei
W
Fan
Pei G
PG
Yan
Shu T
ST
Li
Shao H
SH
D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D005453:Fluorescence; D005638:Fruit / Q000378:metabolism*; D007700:Kinetics; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism*; D027861:Prunus / Q000201:enzymology / Q000378:metabolism*; D013696:Temperature
D002734:Chlorophyll; D002245:Carbon Dioxide