One of the main problems of rendering outdoor scenes in real time is the representation of trees and plants. The modeling tools for vegetal species generate polygonal models with such a great geometric complexity that they need efficient techniques for achieving an interactive visualization. In this article we present a LOD model based on the geometric representation of leaves that eliminates b...

Changes in phosphate metabolism were explored in discs from tobacco (Nicotiana tabacum) leaves of three contrasting types: green leaves which were fully expanded and attached to the plant, leaves which had yellowed following excision and dark starvation, and leaves which had yellowed while attached to the plant. 2,4-Dinitrophenol at 10(-5)m stimulated the respiration rate of discs from green an...

BACKGROUND Many tropical forest tree species delay greening their leaves until full expansion. This strategy is thought to provide newly flushing leaves with protection against damage by herbivores by keeping young leaves devoid of nutritive value. Because young leaves suffer the greatest predation from invertebrate herbivores, delayed greening could prevent costly tissue loss. Many species tha...

Prunus domestica L. has green leaves, whereas Prunus cerasifera Ehrh. var. atropurpurea has red leaves due to the presence of mesophyll anthocyanins. We compared morphological and photosynthetic characteristics of leaves of these species, which were sampled from shoots grafted in pairs on P. domestica rootstocks, each pair comprising one shoot of each species. Two hypotheses were tested: (1) an...

The most photosynthetically active leaves of rice seedlings were severely damaged when shoots but not roots were chilled (10°C/25°C, respectively), but no such injury was observed when the whole seedling was chilled (10°C/10°C). To elucidate the mechanisms, we compared the photosynthetic characteristics of the seedlings during the dark chilling treatments. Simultaneous analyses of Chl fluoresce...

A pattern of seasonal changes in the morphological and anatomical leaf traits is reported for Potentilla argentea L. var. tenuiloba (Jord.) Sw. of temperate-climate areas in central Poland. Leaf area, perimeter, dry mass and lamina thickness were measured in summer and autumn leaves of the same individuals. Dissection index, density and specifi c leaf area were calculated. Signifi cant differen...

introduction: multileaf collimator (mlc) is state of the art among the radiation field shaping systems for conformal radiotherapy techniques. some advantages of this system are as follow: reduction of treatment time, higher precision in conforming the radiation field to the projection of the target volume and lowering the chance of errors made by technologists. the purpose of this research was ...

There is a growing interest in simulating natural phenomena in computer graphics applications. Animating natural scenes in real time is one of the most challenging problems due to the inherent complexity of their structure, formed by millions of geometric entities, and the interactions that happen within. An example of natural scenario that is needed for games or simulation programs are forests...

A pressure chamber was used to measure matric potentials of frozen and thawed leaves. Significant matric potentials were demonstrated in sunflower (Helianthus annuus L.), yew (Taxus cuspidata Sieb. and Zucc.), and rhododendron (Rhododendron roseum Rehd.). Matric potentials were particularly negative in rhododendron and were correlated with the amount of cell wall present and with the volume of ...

We prove that a codimension one foliation of an orientable paracompact manifold has at most a countable number of nonorientable leaves. We also give an example of a codimension one foliation of a compact orientable manifold with an infinite number of nonorientable leaves. Introduction. The purpose of this paper is to investigate the occurrence of nonorientable leaves in a codimension one foliat...