BACKGROUND AND AIMS Epidermal phenolic compounds (mainly flavonoids) constitute a vital screen that protects the leaf from damage by natural ultraviolet (UV) radiation. The effectiveness of epidermal UV-screening depends on leaf anatomy, the content of UV-screening compounds and their spatial uniformity over the leaf area. To investigate in vivo the spatial pattern of the epidermal UV-screen du...

Canopy photosynthesis models have predicted an optimal leaf area index (LAI; leaf area per unit surface area) and leaf nitrogen distribution at which whole-plant carbon gain per unit N is maximized. In this study we experimentally tested these models, using transgenic P(SAG12)-IPT tobacco (SAG; Nicotiana tabacum L.) plants with delayed leaf senescence and therefore a greater LAI and more unifor...

A new instrument called a Multiband Vegetation Imager (MVI) (Kucharik et al., 1997), which uses a 16-bit charge-coupled device (CCD) camera and ®lter exchange mechanism to capture 2-band (visible and near-infrared) image pairs of plant canopies, has been used to measure the light distribution over sunlit leaves and indirectly infer leaf area index (LAI), sunlit LAI and leaf angle distribution (...

The relationships between foliar weight/leaf area and four stem dimensions (dbh, total stem cross-sectional area, total sapwood area, and current sapwood area at breast height) were investigated in two important bottomland tree species of the southern United States, cherrybark oak (Quercus falcata var. pagodifolia EN.) and green ash (fraxinus pennsylvanica Marsh.). In all models tested and for ...

In some conifers, shoot geometry and needle morphology vary significantly in response to the light conditions under which they develop. We measured shoot length, silhouette area, total projected needle area, total needle weight and needle thickness on current shoots developed under a wide range of light conditions in a 36-year-old Abies amabilis (Dougl.) Forbes stand. Current light was quantifi...

We quantified stand leaf area index and vertical leaf area distribution, and developed canopy extinction coefficients (k), in four mature hardwood stands. Leaf area index, calculated from litter fall and specific leaf area (cm*.g-‘), ranged from 4.3 to 5.4 m*.rn-r. In three of the four stands, leaf area was distributed in the upper canopy. In the other stand, leaf area was uniformly distributed...