© 2007 Heron Publishing—Victoria, Canada
Photosynthesis in response to sink–source activity and in relation to end products and activities of metabolic enzymes in
peach trees
Wei D. Li (1, 2), Wei Duan (1), Pei G. Fan (1), Shu T. Yan (1) and Shao H. Li (1, 3)
1. Institute of Botany, The Chinese Academy of Sciences, 100093 Beijing, P.R. China () / 2. Institute of Mountainous Areas Research, Hebei Agricultural University, 071001 Baoding, P.R. China / 3. Corresponding author (shhli@ibcas.ac.cn) / Received July 28, 2006; accepted December 4, 2006; published online June 1, 2007
Summary
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 (Pn), 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 (Tl) was higher in the –fruit treatment than in the +fruit treatment, and Pn decreased in the –fruit treatment, especially when Tl exceeded 38 and 36 °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 Tl exceeds a critical temperature under conditions of decreased sink demand. Decreased stomatal aperture and increased Tl may regulate photosynthesis by affecting electron transport.
Keywords:
enzyme activity, leaf temperature, maximal fluorescence, minimal fluorescence, net photosynthetic rate, photochemical efficiency,
stomatal conductance, transpiration rate.
