VARIATION OF STOMATAL CONDUCTANCE AND ITS CONTROLLING FACTORS OF DIFFERENT SPECIES IN A WET EVERGREEN FOREST IN THE MID·COUNTRY WET ZONE OF SRI LANKA

Stomatal conductance is a primary determinant of the net carbon balance and growth of differentplant species in a forest community. Because of its influence on transpirational water loss, stomatalconductance determines the water balance of a plant. As both carbon and water balances playimportant roles in survival and establishment of seedlings of different plant species in a forestcommunity, stomatal conductance has a direct influence on species composition and succession of aforest. Therefore, the main objective of the present study was to describe the inter-species variationof stomatal conductance in a wet, evergreen forest in the mid-country wet zone of Sri Lanka. Asecondary objective was to examine the variation of two parameters which could influence stomatalopening, namely incident light intensity and leaf temperature, and to see whether any directcorrelations can be established between stomatal conductance and the above parameters.This study was conducted in the Gannoruwa forest reserve in Kandy in September, 1997. 108 plantspecies which included all growth forms (i.e. trees, shrubs, herbaceous plants, vines and grasses)were found. Stomatal conductance was measured using a portable diffusion porometer which alsorecorded the incident light intensity ( in terms of photosynthetically-active radiation) and leaftemperature. Conductances of both upper and lower leaf surfaces were measured and total leafconductance was obtained by summing the two above measurements. In a given species, at leastthree plants were sampled.There were significant differences between species in lower surface conductance (gi), upper surfaceconductance (gu) and total leaf conductance (g). Except in one species, gl was greater than gu in allother species examined. Lower Surface Conductance/g, ) ranged from 17 to 1280 mmol m,2 S'I with amean of 175.8 += 8.9 mmol m ,2S'I whereas gu ranged from 2.36 to 252 mmol m,2 S'I with a mean of25.15 += 1.58 mmol m,2 S'I. The range of total conductance (g) was 20.45 - 1309.8 mmol m,2 S'Iwith a mean of 20 1.41 += 9.44 nunol m,2 S'I. The frequency distributions of aH three conductanceparameters (i.e. lower, upper and total) were skewed to the left with the respective median valuesbeing 132.5 (for gr ), 18.25 (gu) and 149.9 (g) mmol rn" S'I . Normality of the distributions whentested using the box plot technique, showed significant skewness to the left, Deletion of extremevalues did not improve normality significantly.The light intensities experienced by the leaves ranged from 2.5 to 1830 umol (PAR) m ,2S'I and theleaf temperatures ranged from 24.55 to 34.40 C. When all species were considered together, totalleaf stomatal conductance (g) had a significant positive correlation with light intensity. But, therewas no significant correlation between g and leaf temperature. Similar results were obtained whenlower and upper surface conductances were considered separately as well. There was a highlysignificant positive correlation between light intensity and leaf temperature. A multiple regressionanalysis showed that these two variables explained only 8% of the overall variation of leaf stomatalconductance. This infers species differences, interactions between species, and their response tovariations in light intensity and leaf temperature are more significant. Stomatal conductance ofditTerent species respond in ditTerent degrees to light and temperature variations.1\ cluster analysis allowed the 108 plant species examined to be grouped in to different categorieson the basis of their total leaf stomatal conductance (g). The different species groups could bebroadly related to their position in the successional sequence. It was found that the speciesestablished under the canopy on the forest floor generally had lower levels of g than thoseestablishing in canopy gaps. While many species of the latter group (growing in gaps) had the abilityto raise their stomatal conductance in response to increasing light intensity, most species of theformer group (growing under the canopy shade) could not respond to the occasional sunflecks thatare incident on them at different times of the day.

Climate change and agricultural adaptation in Sri Lanka: a review

Climate change is inevitable and will continue into the next century. Since the agricultural sector in Sri Lanka is one of the most vulnerable to climate change, a thorough understanding of climate transition is critical for formulating effective adaptation strategies. This paper provides an overview of the status of climate change and adaptation in the agricultural sector in Sri Lanka. The review clearly indicates that climate change is taking place in Sri Lanka in terms of rainfall variability and an increase in climate extremes and warming. A number of planned and reactive adaptation responses stemming from policy and farm-level decisions are reported. These adaptation efforts were fragmented and lacked a coherent connection to the national development policies and strategies. Research efforts are needed to develop and identify adaptation approaches and practices that are feasible for smallholder farmers, particularly in the dry zone where paddy and other food crops are predominately cultivated. To achieve the envisaged growth in the agricultural sector, rigorous efforts are necessary to mainstream climate change adaptation into national development policies and ensure that they are implemented at national, regional and local levels

Ultrasonic processing of milk and dairy products

The application of ultrasound to conventional dairy processes has the potential to provide significant benefits to dairy industry such as possible cost savings and improved product properties. Moreover, the appeal of ultrasound as a processing technique has been regarded safe compared to other emerging technologies. During the past decade, the technology has rapidly emerged as a mild nonthermal processing tool capable of replacing or assisting many conventional dairy processing applications such as inactivation of microbes and enzymes, homogenization and emulsification, creaming, crystallization, and functionality modifications within dairy systems. These aspects are highlighted in this chapter

Low intensity ultrasound applications on food systems

Ultrasound is composed of sound waves with frequency beyond the limit of human hearing. Ultrasound techniques are relatively cheap, simple and energy saving, and thus became an emerging technology to be used for food processing. Ultrasound technology used in food systems are divided as low and high intensity ultrasound applications. The changes to the physical properties of ultrasound, such as scattering, attenuation and acoustic velocity caused by food materials have been used in food quality assurance applications and will be discussed for selected food systems which are of importance to Australian export industry

Whey Wastes and Powders

Whey has primarily been considered a waste by the dairy industry. However, strict environmental regulations prevented disposal of untreated liquid whey. Production of whey powders were among the most popular conversions of liquid whey. The recent advances in the processing techniques are aimed at producing a variety of milk powders consisting of excellent physical and functional properties which are preserved during storage. However, the powder structure is strongly affected by the composition of the liquid feed and the processing conditions. For instance, powders produced by roller drying has a compact structure with less occluded air, while spray dried powder particles are spherical containing occluded air, either as a large central vacuole or smaller vacuoles distributed through the interior of the particles. Another instance, high inlet temperature of the spray drier results in a more wrinkled surface, while the presence of high concentrations of proteins in the liquid feed results in a smooth surface. The present chapter focuses on different whey waste stream powders, processing methods and their microstructure as affected by the processing and compositional changes

High power ultrasound processing in milk and dairy products

Ultrasound has been known to create material changes through physical and chemical reactions. The homogenization effect of ultrasound is one of the most recognizable traits of the technology. This chapter explores the dairy applications in response to ultrasound treatment in a more descriptive manner. The efficiency of ultrasonic sonication is driven by several other important factors in addition to frequency, such as power. Membrane technology is currently used in the dairy industry for a variety of applications, such as separation of milk components, concentration of protein levels for spray drying and more. The chapter focuses on the effects of ultrasound on bulk physical and functional properties of casein-containing systems and their respective secondary dairy products. Controlling the viscosity of dairy streams with ultrasound is one of the most promising applications to have recently emerged. The thermal stability of whey proteins during heating is a major continuing processing issue

Real time stereo vision based on biologically motivated algorithms using GPU

Although many recent stereo vision algorithms have been able to create disparity maps with high accuracy, because of the sequential nature it is difficult to adopt them for real time applications. Biologically motivated algorithms involving Gabor filters demonstrate inherent parallelism and could be effectively implemented in parallel hardware such as Graphics Processing Units(GPUs). We present a real time stereo vision algorithm based on Gabor filters which effectively use the memory hierarchy and the threading resources of the Graphics Processing Unit(GPU). Since the 2D filtering process is a critical activity which takes upto 50% of the total time to create the disparity map, we evaluate the GPU implementation of three filtering methods. Using the optimal filtering method out of them, we were able to achieve a frame rate of 76 fps for a 512x512 image stream on a NVIDIA GTX 480 GPU, and a I70x speed-up compared to the conventional CPU based implementation

Exposición del Presidente de la Junta de Comercio.

Documento en el que se reproduce el informe que Gregorio Obregón, presidente de la Junta de Comercio de Bogotá, presenta sobre las mejoras y modificaciones que se han realizado en Bogotá, respecto al servicio de serenos y alumbrado público en la ciudad. A lo largo del informe se hace hincapié en los diferentes reglamentos vigentes para la administración de los servicios públicos y se presentan balances de liquidación y estado general de los rubros destinados para este fin

Application of ultrasound to reduce viscosity and control the rate of age thickening of concentrated skim milk

Concentrated skim milk was treated with high intensity low frequency ultrasound (20 kHz) to lower viscosity through a process of acoustic cavitation. Batch sonication for 1 min at 40-80 W, and continuous treatment delivering an applied energy density of 4-7 J mL-1, reduced the viscosity of medium-heat skim milk concentrates containing 50-60% solids. Viscosity was reduced by approximately 10%, but this improved to >17% in highly viscous age thickened material. Sonication also changed the shear thinning behaviour at shear rates below 150 s-1. Although ultrasound lowered the viscosity of skim milk concentrated to ≥50% solids, the treatment could only delay the rate of thickening once the ageing process was established. It was only when ultrasound was activated during concentration that sonication prevented the viscosity of skim milk concentrates from increasing rapidly