Comparison of Campbell-leaf press with standard plant water stress measurements for four species

The Campbell-Brewster (J-14) leaf press is a compact alternative to the pressure chamber for plant water potential determination. Data comparing the J-14 with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) are limited. All three J-14 end points (exudation from cut or uncut leaf edges or darkening of interveinal areas) were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. Our data shoved a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean for all but comparisons with CWSI or Tc minus air temperature (?T), and for corn for ?x only. The J-14 did not perform well for tomato or rapeseed. Failure of J-14 or ?x, to correlate well with CWSI suggests difficulty with CWSI measurement under humid southeastern conditions

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

Numerous techniques are currently available for measurement of plant water status in field environments, including pressure chambers and indices based upon infrared-determined canopy temperatures. The Campbell-Brewster (J-14) leaf press has been promoted as a compact alternative to the pressure chamber for plant water potential determination. In-depth comparisons of the J-14 (?J) with the pressure chamber (?x) or with canopy temperatures (Tc) and crop water stress index (CWSI) have been limited, and an evaluation of the technique in a humid environment was needed. All three J-14 end points [exudation from cut (?Jc) or uncut leaf edges (?Ju) or darkening of interveinal areas (?Jd)] were highly correlated among themselves for the four species studied. Correlations of J-14 end points with other stress indicators from unstable diurnal periods were poor. None of the water status indicators correlated well with leaf diffusive resistance. Our data showed a species-related reliability of the J-14. The J-14 produced r2 values above 0.7 for soybean [Glycine max. (L.) Merr.] for all but comparisons with CWSI or Tc, minus air temperature (?T), and for corn (Zea mays L.) for ?x only. The J-14 did not perform well for tomato (Lypersician esculentum Mill.) or rapeseed (Brassica napes L.), and is probably best regarded only as a relative indication of plant water status in the absence of calibration with other techniques. Failure of ?x or J-14 to correlate well with CWSI underscores difficulty with CWSI measurement under humid conditions

Effect of early and late planting on sunflower performance in the southeastern United States

Current sunflower (Helianthus annuus L.) production worldwide occurs predominantly in mid-latitude and humid continental climates [2], especially the latter. The potential for using sunflower in systems that produce more than one agronomic crop per year (double or multiple cropping) is generally limited to warm areas with long growing seasons, such as the southern United States. This climatic area corresponds to the humid subtropic climate zone which also occurs in significant continental areas of eastern south-central South America (Paraguay, Uruguay, and parts of Brazil and Argentina), southern China, and the eastern coastal areas of Australia

A particle system with explosions: law of large numbers for the density of particles and the blow-up time

Consider a system of independent random walks in the discrete torus with creation-annihilation of particles and possible explosion of the total number of particles in finite time. Rescaling space and rates for diffusion/creation/annihilation of particles, we obtain a stong law of large numbers for the density of particles in the supremum norm. The limiting object is a classical solution to the semilinear heat equation u_t =u_{xx} + f(u). If f(u)=u^p, 1<p \le 3, we also obtain a law of large numbers for the explosion time

Visual cues from different trap colours affect catches of Sahlbergella singularis (Hemiptera: Miridae) in sex pheromone traps in Cameroon cocoa plantations

Cocoa mirids, Sahlbergella singularis and Distantiella theobroma, are the most economically important insect pests of cocoa in West and Central Africa, where they can cause up to 40% losses in cocoa yields. Sahlbergella singularis is the most common species in Cameroon and was therefore targeted in this study. During a two-year trial in 15 cocoa plantations in Ayos and Konye, in the Centre and Southwest regions of Cameroon respectively, the most effective colour – white, purple or green – of sex pheromone traps was examined for integration into mirid management programmes. Similar temporal patterns in S. sahlbergella male trap catches were observed with all three colours, but the green trap caught more S. singularis (Ayos: 0.968 ± 0.091 [SEM]; Konye: 0.640 ± 0.076/trap/month) compared with purple traps (Ayos: 0.674 ± 0.068; Konye: 0.441 ± 0.058), and white traps (Ayos: 0.467 ± 0.049, Konye: 0.253 ± 0.041). Trap reflectance showed wavelength peaks typical for purple in both short (approximately 380 - 480 nm) and long wavelengths (> 650 nm), and ~530 nm for green. Reflectance peaks exceeded 100% of the incident light in the 400-450 nm range from the white, suggesting the presence of optical brighteners. Trap catches support the hypothesis that S. singularis ocelli are more responsive to light of shorter wavelengths. Despite the low attractiveness of the sex pheromone to S. singularis, a optimisation of the colour of the trap can improve S. sahlbergella monitoring, mass trapping, and other control measures which could ultimately lead to reductions of insecticide use and to conservation of beneficial arthropods, particularly cocoa flower pollinators that are critical for improving cacao tree productivity

Broad-scale patterns of body size in squamate reptiles of Europe and North America

Aim To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients. Location North America and western Europe. Methods We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 x 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data. Results Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%. Main conclusions Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone