title: Integrating within-crown variation in net photosynthesis in loblolly and slash pine families.
abstract: We examined photosynthetic characteristics of two fast- and two slow-growing half-sib families of both loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii var. elliottii Engelm.) on two sites in northern Florida to: (1) quantify variation in light-saturated net photosynthesis (Amax) associated with vertical crown position and foliage age; (2) quantify the amount and distribution of leaf area by foliage age class; and (3) determine whether photosynthetic indices, ranging from leaf-level through whole-crown Amax, were related to growth differences among species and families. In both species, leaf-level Amax was higher in more recently formed foliage both within the same year (where Amax in the third flush averaged 10 to 30% higher than Amax in the first flush) and between years (where Amax in current-year foliage averaged 20 to 40% higher than Amax in 1-year-old foliage). When expressed on a leaf area basis, Amax of current-year foliage was higher in slash pine than in loblolly pine, but Amax expressed on a mass basis did not differ between species. Loblolly pine had higher whole-tree leaf area than slash pine, whereas whole-tree Amax did not differ between species. When the mean values for fast-growing families were compared with the mean values for slow-growing families, there were no differences in leaf-level characteristics, whereas at the whole-tree level, fast-growing families had higher leaf area and whole-tree Amax than slow-growing families in both species. When comparisons were made among the individual fast- and slow-growing families, however, results were more variable. In both species, stem volume growth was strongly correlated with whole-tree Amax, with most of the strength of the correlation deriving from the relationship between volume growth and tree leaf area.
authors.affiliation: School of Forest Resources and Conservation, University of Florida, Gainesville, FL, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: McGarvey
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Martin
authors.forename: Timothy L
authors.initials: TL
authors.lastname: White
mesh_terms: D014644:Genetic Variation; D010788:Photosynthesis / Q000502:physiology*; D028223:Pinus / Q000502:physiology*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology; D014197:Trees / Q000502:physiology*