Differences in susceptibility to Oedema in two Tomato cultivars growing under various light intensities

Oedema was found in tomato plants grown under controlled conditions of 23°C day and 13°C night temperatures, high relative humidity (80%), and irrigation to saturation. Three light intensities were tested on two cultivars, Hosen Eilon and Viresto. There were considerable differences in their response, and in the degree of disease incidence, under the different light intensities. In cv. Hosen Eilon the disease appeared in all three light treatments; the disease symptoms increased in severity as light intensity declined. Cv. Viresto showed no signs of the disease.     

Zinc tolerance in the ant species Myrmica rubra originating from a metal pollution gradient

This study was designed to test whether the ant species Myrmica rubra had developed a tolerance to metal pollution. Larvae and workers, collected from seven sites located along a metal pollution gradient in the vicinity of Olkusz, Poland were exposed to a range of Zn concentrations in food, artificially contaminated in a laboratory experiment. The mortality of adults and larvae, as well as maximum larvae body mass, was recorded. The results of this study indicate that larvae mortality was independent of the site pollution, but decreased significantly with the Zn concentration in food. Opposite results were found for workers: irrespectively of Zn concentration in the food, the mortality decreased with site pollution, indicating enhanced metal tolerance in workers. Contrary to the expectations, the maximum larvae mass estimated with the von Bertalanffy curve, increased by the pollution gradient. Larvae were more sensitive to Zn than the adults, but their higher mass at the most polluted sites, may have enhanced tolerance to metal pollution.     

Application of Computer‐assisted Sperm Analysis in Selecting the Suitable Solution for Common Carp,Cyprinus carpio L., Sperm Motility

The common carp, Cyprinus carpio L., sperm motility parameters were analyzed by using computer‐assisted sperm analysis system. The percentage of motile sperm (MOT, %), progressively motile sperm (PRG, %), curvilinear velocity (VCL, µm/sec), average path velocity (VAP, µm/sec), the wobbling index (WOB, %), movement linearity (LIN, %), beat cross frequency (BCF, Hz), and amplitude of lateral head displacement (ALH, µm) were determined. Five activation solutions (As) were used to activate sperm movement. As 1 solution: 68 mM NaCl, 50 mM urea, 0.5% bovine serum albumin (BSA), pH: 7.7, 181 mOsm/kg; As 2 buffer: 100 mM NaCl, 10 mM Tris, 0.5% BSA, pH: 9.0, 199 mOsm/kg; As 3 solution: 86 mM NaCl, 0.5% BSA, pH: 7.4, 167 mOsm/kg; As 4 buffer: 5 mM KCl, 45 mM NaCl, 30 mM Tris, 0.5%, pH: 8.0, 160 mOsm/kg; and As 5 solution: distilled water with the addition of 0.5% BSA, pH: 7.3, <3 mOsm/kg. Among five tested solutions, a buffer with a pH of 9.0 and osmolality of approximately 200 mOsm/kg (As 2) was the most suitable. After its activation, a significant increase in MOT and ALH values was observed, which can be of importance to the effectiveness of egg fertilization .     

Interactive effects of drought and edge exposure on old-growth forest understory species

Landscape Ecology - Both climatic extremes and land-use change constitute severe threats to biodiversity, but their interactive effects remain poorly understood. In forest ecosystems, the effects...     

Dynamic chloroplast pigments concentration in leaves of soybean ( Glycine max [L.] Merr.) under reduced tillage

The objectives of this experiment were to determine the chloroplast pigments dynamics of soybean leaves during the growth stages under different tillage systems, which can be a major factor limiting yield of soybean. The greatest differences between the photosynthetic productivity parameters of the investigated soybean were determined from reproductive stages (R2 and R3?–?4). The chlorophyll a, chlorophyll a/b and carotenoids content under CT, DH and NT were greater in the reproductive stages (R2 and R3?–?4) than in the early stages (V3?–?4 and R1). The concentration dynamics of chlorophyll b and chlorophyll a/b was very similar in all growth stages and under all tillage systems in the 2-yr average. The increased drought stress in 2003 was likely critical in the observed lower seed yields in 2003. The yield of soybean was significantly lower under NT than CT and DH treatments in both years. The relationship between the soybean yield and chloroplast pigments concentration is strongly influenced by external factors. In the 2-yr average the soybean yield was considerably affected by the years and tillage systems. Statistical analysis showed a very significant relationship between chlorophyll pigments content, but photosynthetic parameters investigated did not correlate with soybean yield.     

Strawberry Cultivation Studies III. Spaced and Matted Systems

The immediate cause of the mechanically weak unions that occur in some incompatible trees is by now well known. They are due to the abnormal arrangement of the xylem tissue, particularly the fibres, which, instead of interlocking across the union, either curve in a horizontal direction or are separated by a layer of parenchymatous tissue. This has been well described by Proebsting (1928), Bradford and Sitton (1929), Eames and Cox (1945), Herrero (1951) and others. All are agreed that the discontinuity of the vascular tissues is due to some interruption, temporary or permanent, of normal cambial activity at the point of union, but there is as yet little information regarding the basic causes of this interruption. Most anatomical investigations of the union have been concerned primarily with the structure of the woody cylinder, although, as long ago as 1929, Bradford and Sitton wrote, “ the break-down in the bark seems more consistent, more complete and perhaps more important than that in the wood ”. The first attempt to explain the break in cambial continuity was made by Herrero (1951) who concluded from his anatomical investigations that there existed in incompatible combinations a latent antagonism between adjoining cells of stock and scion, and that spontaneous breaks occurred in the cambial layer at the point of union, possibly in connection with changes undergone at the union by substances elaborated in the leaves. Thiel (1954) agrees that the underlying causes of pear/quince incompatibility are probably biochemical in nature. It is believed that further evidence for this view is provided by observations which have been made at East Mailing on the histology of the bark tissue in some pear/quince unions and which will be described in this paper.     

Cuticular cracking in pepper fruit. I. Effects of night temperature and humidity

Summary

The objective of the present study was to characterize some of the anatomical and physiological characteristics of fruit cracking in bell pepper (Capsicum annuum L.). Scanning-electron micrographs show that initiation of fruit cracking in bell pepper is by formation of mini-cracks on the cuticle layer; these then enlarge into cracks and traverse the epidermal cells. Pepper cultivars differ in their sensitivity to cracking, partly because of differences in fruit pericarp thickness. Limitation of night transpiration by high humidity or low temperature increased the turgor potential of the fruit pericarp and enhanced cracking. Likewise, leaf pruning suppressed night transpiration and concomitantly increased cracking. Fruit cuticle transpiration was found to be low in the early stages of fruit development and to increase as the fruit became susceptible to cracking. Environmental conditions which enhanced cracking also increased cuticle transpiration in a sensitive pepper cultivar but not in a less sensitive one. We suggest that fruit cracking in bell pepper occurs because reduction in night transpiration causes high turgor pressure in the fruit. As the cuticle becomes permeable to water, the inner turgor pressure causes the cuticle to crack. Differences in cultivar sensitivity may be partly due to differences in pericarp thickness and cuticle properties, but additional factors may be involved.