414 The Effect of Water Availability on Rose Photosynthesis and Calorespirometric Properties

Rose plants (cv. Kardinal, grafted on Natal Brier) were grown in UC mix (42% fir bark, 33% peat, and 25% sand) and in coir. Water tension in the media was maintained within a predetermined narrow range using electronic tensiometers. Whole plant net photosynthesis as a function of the water tension in the medium was determined and the results were later normalized to measured leaf area. Simultaneous measurements of metabolic heat and respiration rate were carried out on detached young (FW = 10-20 mg.) leaflet samples, using differential scanning calorimeter (model 4100, Calorimetry Sciences, Provo, Utah). Only a small amount of plant material is removed for analyses so the assay is essentially non-destructive for the whole plant. Physical characteristics of the media greatly affect the relationship between water tension and water availability to plants. At similar tension values, water availability is much lower in coir than in UC mix. The effects of water availability on net photosynthesis, metabolic heat rate, and respiration will be discussed in relation to their effect on productivity.

Selection for biomass production based on respiration parameters in eucalypts: effects of origin and growth climates on growth rates

Seventeen Eucalyptus species and 30 rapid-growing Eucalyptuscamaldulensis trees (referred to as plus trees), growing in a plantation were studied to examine relationships among measured plant growth and respiratory parameters, geographical origins, and growth climate. The respiratory parameters measured at two different temperatures by isothermal calorimetry were metabolic heat rate, rate of CO2 production, and the ratio of heat rate to CO2 rate. Metabolic heat rate was also measured as a continuous function of temperature by differential scanning calorimetry in the range of 10 to 40 °C. Tree growth was measured as rates of height and stem volume growth. The values of respiratory and growth variables of Eucalyptus species are significantly correlated with latitude and altitude of origin of their seed sources. The maximum metabolic heat rate, the temperature of the maximum heat rate, the temperature coefficients of metabolic rate, and the temperatures at which the slopes of Arrhenius plots change are all genetically determined parameters that vary both within and among species. Measurement of growth rate–respiration rate–temperature relationships guide understanding of why relative growth rates of Eucalyptus species and individual genotypes differ with climate, making it possible to identify genotypes best suited for rapid growth in different climates. The temperature dependence of respiration rates is an important factor determining relative growth rates of eucalypts in different climates. To achieve optimum biomass production the temperature dependence of individual plants must be matched to growth climate.

Calorimetric evidence for site-adapted biosynthetic metabolism in coast redwood (Sequoiasempervirens)

Uses of recently available calorimetry technology are explored for measurement of metabolic activity–temperature relations in coast redwoods (Sequoiasempervirens (D. Don) Endl.). These redwoods were collected from different parts of the native range and grown in a common-garden plantation. Analysis of metabolic activity from 10 to 55 °C was used to examine site adaptedness of respiratory metabolism in 16 representative clones of coast redwood. Apparent activation energies changed markedly over the range 12–52 °C, but the patterns of change were similar for clones from five geographical regions and thus appear to be general for the species. However, high-temperature stability, the temperature of peak activity, and the peak metabolic heat rate differed substantially among samples from the five regions. Additional variability in high temperature stability and the temperature of peak activity was measured between trees from the same stands within regions. We suggest that the observed regional and clonal variations in high-temperature stability, the temperature of peak activity, and the peak metabolic heat rate are biologically meaningful. These may be used both to understand the adaptive architecture of coast redwood and to select clones likely to be adapted to particular sites or defined ranges of sites.

Prediction of long-term growth rates of larch clones by calorimetric measurement of metabolic heat rates

A linear correlation exists between long-term growth rates and calorimetrically measured metabolic heat rates in some clones of larch (Larixlaricina (Du Roi) K. Koch). The metabolic heat rate per gram of tissue was found to be highly variable among clones from different trees and reproducible for clones of the same tree. The ordering of metabolic rates for clones was shown to be independent of the physiological growth stage in which the measurements were made. Winter-hardened tissue was found to be immediately active on warming to room temperature.