© 2000 Heron Publishing—Victoria, Canada
Influence of nutrient supply on shade–sun acclimation of Picea abies seedlings: effects on foliar morphology, photosynthetic performance and growth
G. Grassi (1) and G. Minotta (1)
1. Dipartimento di Colture Arboree, Univ. di Bologna, via Filippo Re 6, I-40126 Bologna, Italy / Received July 22, 1999
Summary
Norway spruce seedlings (Picea abies Karst.) were grown in low light for one year, under conditions of adequate and limiting nutrition, then transferred to high
light. Three months after transfer we measured photosynthesis, leaf nitrogen concentration, leaf chlorophyll concentration
and leaf mass per area (LMA) of current-year and 1-year-old shoots; silhouette area ratio (SAR, the ratio of shoot silhouette
area to projected needle area) was also measured in current-year shoots.
At the foliage level, the effects of light and nutrient treatments differed markedly. Light availability during foliage expansion
primarily affected LMA and SAR (morphological acclimation at the needle and shoot level, respectively). By contrast, nutrient
supply in high light affected photosynthetic capacity per unit of leaf tissue (physiological acclimation at the cellular level)
but did not affect LMA and SAR. The capacity for shade–sun acclimation in foliage formed before transfer to high light differed
greatly from that of foliage formed following the transfer. The morphological inflexibility of mature needles (measured by
LMA) limited their shade–sun acclimation potential. In contrast, at high nutrient supply, shoots that developed just after
the change in photosynthetic photon flux density largely acclimated, both morphologically and physiologically, to the new
light environment. The acclimation response of both current- and 1-year-old shoots was prevented by nutrient limitation. Analysis
of growth at the whole-plant level largely confirmed the conclusions drawn at the shoot level. We conclude that nutrient shortage
subsequent to the opening of a canopy gap may strongly limit the acclimation response of Norway spruce seedlings. Successful
acclimation was largely related to the plant's ability to produce sun foliage and adjust whole-plant biomass allocation rapidly.
Keywords:
biomass allocation, leaf mass per area, light acclimation, nitrogen, Norway spruce, photosynthesis, silhouette area ratio.
