105 °C for 15 min, dried at 75 °C for 72 h, and the dry weight was measured. The relative growth rate was defined as the parameter RGR in the equation ( Hunt, 1990 ): , where W1 and W2 are the whole plant fresh weights at times t1 (at 0 h of the
Huai-Fu Fan, Wen Chen, Zhou Yu, and Chang-Xia Du
Jun Zhu, Duane P. Bartholomew, and Guillermo Goldstein
Despite the potential impact of rising global CO2 levels, only a limited number of studies have been conducted on the effects of ambient and elevated CO2 on plants having Crassulacean acid metabolism (CAM). To our knowledge, there are no studies for pineapple [Ananas comosus (L.) Merr.], the most commercially important CAM plant. Pineapple plants were grown at CO2 levels of ≈330 (ambient) and ≈730 (elevated) μmol·mol-1 in open-top chambers for 4 months. The mean air temperature in the chambers was ≈39 °C day/24 °C night. Average plant dry mass at harvest was 180 g per plant at elevated CO2 and 146 g per plant at ambient CO2. More biomass was partitioned to stem and root but less to leaf for plants grown at elevated CO2; leaf thickness was 11% greater at elevated than at ambient CO2. The diurnal difference in leaf titratable acidity (H+) at elevated CO2 reached 347 mmol·m-2, which was up to 42% greater than levels in plants grown in ambient CO2. Carbon isotopic discrimination (Δ) of plants was 3.75% at ambient CO2 and 3.17% at elevated CO2, indicating that CO2 uptake via the CAM pathway was enhanced more by elevated CO2 than uptake via the C3 pathway. The nonphotochemical quenching coefficient (qN) of leaves was ≈45% lower in the early morning for plants grown at elevated than at ambient CO2, while afternoon values were comparable. The qN data suggested that the fixation of external CO2 was enhanced by elevated CO2 in the morning but not in the afternoon when leaf temperature was ≥40 °C. We found no effect of CO2 levels on leaf N or chlorophyll content. Pineapple dry matter gain was enhanced by elevated CO2, mainly due to increased CO2 dark fixation in environments with day temperatures high enough to suppress C3 photosynthesis.
Neil Mattson and Heiner Lieth
85% relative humidity. Average daily temperature was 22.7 °C (day temperature 24 °C, night temperature 20 °C). The relative growth rate [RGR (g·g −1 ·d −1 )] of plants and roots (estimated as root volume) during the 20-d deprivation period was
E.W. PAVEL and T.M. DEJONG
The fruit growth of three peach (Prunus persica (L.) Batsch cvs. `Spring Lady', `Flamecrest', `Cal Red') and two apple cultivars (Malus domestica Borkh. cvs. `Cox Orange', `Golden Delicious') was measured weekly during the 1988 growing period. Seasonal patterns of fruit relative growth rate calculated on a dry weight basis were very similar for both species. Changes in nonstructural carbohydrate composition of peach mesocarp and apple pericarp were correlated with the two physiological phases of sink-activity of the relative growth rates Changes in sucrose concentrations seemed to coincide with increasing dry matter accumulation for both species, even though fructose was a dominant sugar in apples.
Giuseppe Cimò, Riccardo Lo Bianco, Pedro Gonzalez, Wije Bandaranayake, Edgardo Etxeberria, and James P. Syvertsen
experiment, 32 d later. Stem relative growth rate (RGR) was calculated using the difference between total stem length at the beginning and the end of the experiment divided by the number of elapsed days between the two measurements (cm·m −1 ·d −1 ). Girdling
Dan Drost, Taunya Ernst, and Brent Black
the production cycle compared with the open control. However, as the trial progressed, differences in RGR between the cover treatments were not detected. Fig. 2. Relative growth rates (g·g −1 ·d −1 ) for Fall 2010 and 2011 (Panels A and B ) and
Bryan J. Peterson and William R. Graves
the RGR of the western and eastern Sambucus by 42% and 28%, respectively. Fig. 1. Relative growth rate of seedlings of Sambucus and Ptelea grown for 35 and 38 d, respectively, under six conditions of root-zone moisture. Each circle represents the
Thomas E. Marler and Yasmina Zozor
Growth and leaf gas-exchange responses of carambola (Averrhoa carambola L.) seedlings to wind or seismic stress were studied under glasshouse conditions. Forty days of twice daily seismic stress applied for 10 seconds consistently reduced carambola height, leaf area, dry weight, relative growth rate, and leaf-area ratio, but increased trunk cross-sectional area compared with plants receiving no seismic stress. Fifty-one days of wind load reduced plant height, leaf area, dry weight, trunk cross-sectional area, net assimilation rate, relative growth rate, leaf-area ratio, and stomatal conductance compared with plants receiving no wind stress. Morphological appearance was similar for plants receiving wind or seismic stress. Net CO2 assimilation of carambola leaflets was reduced by 30 minutes of wind load for up to 6 hours following the stress. Results suggest that wind may reduce carambola growth at least partially by influencing leaf gas exchange or by the mechanical stress associated with wind.
Maynard E. Bates
A simple plant growth model has been developed based on the analysis of growth curves of lettuce and spinach in numerous controlled environment experiments. The model incorporates elements for genetic potential, plant spacing, photosynthetic photon flux, photoperiod, environment, and morphology. Predicted parameters are relative growth rate, mean plant weight, and plant growth efficiency. Prediction may be on an hourly or daily basis. Examples drawn from data on various species and cultivars will be presented.
Dana L. Baumann, Beth Ann Workmaster, and Kevin R. Kosola
Wisconsin cranberry growers report that fruit production by the cranberry cultivar `Ben Lear' (Vaccinium macrocarpon Ait.) is low in beds with poor drainage, while the cultivar `Stevens' is less sensitive to these conditions. We hypothesized that `Ben Lear' and `Stevens' would differ in their root growth and mortality response to variation in soil water potential. Rooted cuttings of each cultivar were grown in a green-house in sand-filled pots with three different soil water potentials which were regulated by a hanging water column below a fritted ceramic plate. A minirhizotron camera was used to record root growth and mortality weekly for five weeks. Root mortality was negligible (2% to 6%). Whole plant relative growth rates were greatest for both cultivars under the wettest conditions. Rooting depth was shallowest under the wettest conditions. Whole-plant relative growth rates of `Ben Lear' were higher than `Stevens' at all soil water potentials. `Stevens' plants had significantly higher root to shoot ratios and lower leaf area ratios than `Ben Lear' plants, and produced more total root length than `Ben Lear' at all soil water potentials. Shallow rooting, high leaf area ratio, and low allocation to root production by `Ben Lear' plants may lead to greater susceptibility to drought stress than `Stevens' plants in poorly drained cranberry beds.