Crassulacean acid metabolism (CAM) was investigated in leaves and stems of the succulent C(4) dicot Portulaca oleracea L. Diurnal acid fluctuations, CO(2) gas exchange, and leaf resistance were monitored under various photoperiod and watering regimes. No CAM activity was seen in well watered plants grown under 16-hour days. Under 8-hour days, however, well watered plants showed a CAM-like patte...

Extensive regions of interior Douglas-fir (Pseudotsuga menziesii var. glauca, IDF) forests in North America are being damaged by drought and western spruce budworm (Choristoneura occidentalis). This damage is resulting from warmer and drier summers associated with climate change. To test whether defoliated IDF can directly transfer resources to ponderosa pine (Pinus ponderosae) regenerating nea...

The biology and population dynamics of pine sawfly Diprion pini L. are extremely complex and variable. Among other factors, climatic conditions determine the potential for mass outbreaks of the species. In this paper, we investigate this influence and describe a statistical approach to identify responsible climatic variables in floating time windows, thus identifying the factors responsible for...

Measurements of leaf area index (LAI) taken with photometers such as the LAI2000 are biased by boles and branches which stop part of the light from reaching the photometer. We estimated how much of the sky would be obscurred by boles in an immature stand of Douglas-fir (Pseudotsuga menziesii (Mirb) Franco) that was stem-mapped and of known diameter, height and height-to-live-crown. These yielde...

Shoot growth, chlorophyll concentrations, gas exchange and starch concentrations were studied in lychee (Litchi chinensis Sonn.) seedlings of cultivar "Wai Chee" grown in a heated greenhouse at Nambour in subtropical Australia (27 degrees S). We also examined the effects of shoot defoliation and root pruning on leaf expansion. Shoot growth showed a rhythmic cycle under constant greenhouse condi...

Pine processionary moth (PPM) is one of the most destructive insect defoliators in the Mediterranean for many conifers, causing losses of growth, vitality and eventually the death of trees during outbreaks. There is a growing need for cost-effective monitoring of the temporal and spatial impacts of PPM in forest ecology to better assess outbreak spread patterns and provide guidance on the devel...

The impact of different levels of whole plant partial defoliation (WPPD) on the photosynthesis andprimarymetabolismofwheat,TriticumaestivumL.,was evaluatedat thevegetative and reproductive (grain-Þlling) developmental stages. Photosynthetic parameters such as photosynthesis, stomatal conductance, and transpiration, chlorophyll a ßuorescence, and plant morphological parameters, such asmain stemh...

Phytophagous stink bugs are economically important pests of annual and perennial crops in the southeastern United States. Because of insecticide resistance and risk of secondary pest outbreaks, there is interest in identifying cultural practices that could lead to reduced insecticide applications. The objective of this project was to assess the importance of cotton planting date on stink bug da...

Optimal defense theories suggest that a trade-off between defense costs and benefits maintains genetic variation within plant populations. This study assessed the independent and interactive effects of genetic- and environment-based variation in aspen leaf chemistry on insect performance, preference, and defoliation. Gypsy moth larvae were released into screenhouses containing eight aspen genot...

The January 1998 ice storm broke off tree crowns across a wide geographic area in northeastern North America, and forest tent caterpillar (Malacosoma disstria Hubner) defoliated some of the same stands 2004–2007. We assessed post-event growth responses upper canopy sugar maples (Acersaccharum Marsh.) previously thinned recently rehabilitated even-aged northern hardwood New York State, USA. Core...