Te. Marler et al., DEVELOPMENTAL LIGHT LEVEL AFFECTS GROWTH, MORPHOLOGY, AND LEAF PHYSIOLOGY OF YOUNG CARAMBOLA TREES, Journal of the American Society for Horticultural Science, 119(4), 1994, pp. 711-718
Growth and leaf physiology responses of container-grown 'Arkin' caramb
ola (Averrhoa carambola L.) trees to long-term exposure of almost-equa
l-to 25%, almost-equal-to 50%, or 100% sunlight were studied in four e
xperiments in Guam and Florida. Shading increased rachis length and le
aflet area, and decreased leaflet thickness. Shaded trees also had a m
ore horizontal branch orientation. Shading reduced dark respiration (R
(d)) and light compensation and saturation points but increased chloro
phyll concentration and N-use efficiency. Light-saturated net CO2 assi
milation (A) was not affected by developmental fight level. Trees in f
ull sun had smaller total leaf area, canopy diameter, and shoot : root
ratio and exhibited leaflet movement to avoid direct solar radiation.
Also, trees grown in 100% sunlight had a more vertical branch orienta
tion and greater stomatal density than shaded trees. The ratio of vari
able to maximum fluorescence (F(v)/F(m)) declined during midday in 100
% sunlight trees. This pattern was accompanied by a midday suppression
of A in 100% sunlight-grown trees in Guam. 'Arkin' carambola trees ex
posed to almost-equal-to 25%, almost-equal-to 50%,or 100% sunlight for
up to 39 weeks exhibited physiological and morphological adaptations
that resulted in similar growth. These results indicate that carambola
efficiently adapts to different developmental light intensities.