© 2003 Heron Publishing—Victoria, Canada
Characterization of a type II chlorophyll a/b-binding protein gene (Lhcb2*Pp1) in peach. II. mRNA abundance in developing leaves exposed to sun or shade
Carole L. Bassett (1, 2) and Ann M. Callahan (1)
1. USDA, ARS, Appalachian Fruit Research Station, Kearneysville, WV 25430, USA / 2. Author to whom correpsondence should be addressed (cbassett@afrs.ars.usda.gov) / Received April 2, 2002; accepted September 27, 2002; published online April 1, 2002
Summary
Leaf development of shoots exposed to full sunlight and shoots shaded by the canopy was followed in field-grown, mature peach
trees (Prunus persica (L.) Batsch, cv. Loring) during the first half of the 1995 growing season. The architecture and size of shaded shoots and
sun-exposed shoots differed significantly. Total number of leaves produced on shaded shoots was significantly less than on
sun-exposed shoots throughout the season, and differences in leaf number between light conditions increased as the season
progressed. The overall patterns of leaf development along sun-exposed and shaded shoots were qualitatively similar. The expression
pattern of the type II chlorophyll a/b-binding protein gene, Lhcb2*Pp1, determined by RNA abundance in leaves at different positions along the shoot, was also similar between the two light conditions.
The major difference between sun-exposed and shaded leaves was a lower abundance of Lhcb2*Pp1 RNA in mature, shaded leaves compared with sun-exposed leaves. Although the number of fruit per shoot was significantly lower
on shaded shoots than on sun-exposed shoots, the rate of fruit drop was not substantially different during the growing season,
indicating that quantitative differences in leaf initiation and growth caused by differences in light exposure did not adversely
affect fruit retention. However, based on comparison with a previous study of leaf development in non-fruiting trees, reproductive
development slowed the rate of vegetative growth without affecting the overall pattern of leaf development along the shoots.
Keywords:
fruit trees, gene expression, leaf development, light regulation, photosynthesis.
