The sugars of avocado leaves and leaf disks were labeled by photosynthesis in CO2 during various periods. The label found in the sugars was examined immediately following photosynthesis as well as after a period of respiration under various conditions. Sucrose was found to be the sugar most rapidly labeled during photosynthesis. Mannoheptulose was formed concurrently with sucrose but at a lower...

Net photosynthesis, growth, and ultraviolet (UV) radiation absorbance were determined for the first leaf of Cucurbita pepo L. exposed to two levels of UV-B irradiation and a UV-B radiation-free control treatment. Absorbance by extracted flavonoid pigments and other UV-B radiation-absorbing compounds from the first leaves increased with time and level of UV-B radiation impinging on leaf surfaces...

High midday temperatures can depress net photosynthesis. We investigated possible mechanisms underlying this phenomenon in leaves of Eperua grandiflora (Aubl.) Benth. saplings. This tropical tree establishes in small gaps in the rainforest canopy where direct sunlight can raise midday temperatures markedly. We simulated this microclimate in a growth chamber by varying air temperature between 28...

Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially declines with the canopy depth, and the photosynthetic capacity is affected by light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite heterogenous depending on env...

—After defoliation occurs leaf photosynthetic rate (Pn) can increase, decrease or remain unchanged relative to control uninjured leaves depending on the plant species. With common milkweed Asclepias syriaca (Asclepiadaceae) we conducted 27 experiments with insect herbivory or mechanical tissue removal to examine whether A. syriaca leaf Pn reductions were correlated with the occurrence of gross ...

The use of modern gas analysis instrumentation makes it possible to obtain continuous recordings of transpiration (3, 6, 8, 12, 13, 23) and photosynthesis (4, 5, 16, 19) from intact portions of higher plants. The high sensitivity and rapid response of these instruments permits one to determine rather subtle effects of various internal or environmental factors on physiological processes involvin...

Leaf gas exchange and temperature response were measured to assess temperature acclimation within a tree canopy in climatically contrasting genotypes of Acer rubrum L. Over the course of two 50 d continuous periods, growth temperature was controlled within tree crowns and the steady-state rate of leaf gas exchange was measured. Data were then modelled to calculate the influence of genotype vari...

We measured net photosynthesis, leaf conductance, xylem water potential, and growth of Pinus strobus L. seedlings two years after planting on two clear-cut and burned sites in the southern Appalachians. Multiple regression analysis was used to relate seedling net photosynthesis to vapor pressure deficit, seedling crown temperature, photosynthetically active radiation (PAR), needle N, xylem wate...