SAP TESTING OF NITRATE NITROGEN IN TOMATO

The usefulness of conventional tissue testing techniques is limited for monitoring and adjusting the nitrogen (N) status of rapidly growing crops, such as many vegetables, because of the frequent unavailability of sufficiently quick and reliable test results. The nitrate N status of Lycopersicon esculentum 'Celebrity' was monitored in a greenhouse study using "Merkoquant" quick-test nitrate strips to determine the effects of plant-to-plant variation and variation in leaf position and time of day on the levels of nitrate N detectable in petiole sap. Nitrate N levels decreased from 2800 ppm in 28-day-old plants to below 400 ppm in plants older than 68 days. Sap nitrate N concentrations were equal in the top, middle, and bottom of the canopy of 28-day-old plants, but decreased more rapidly in the top of the canopy as the plants developed. Tissue analysis results and sap test results concurred in showing that N availability had been growth limiting. No differences in sap nitrate concentrations were detected between 10 a.m., 12 p.m., and 2 p.m. ----- La utilidad de tecnicas convencionales para analizar tejidos de plantas para vigilar y ajustir el nivel de nitrogeno en cultivos de creciminento rapido, tales como muchas hortalizas, es limitada debido a la frequente indisponibilidad de resultados suficientes rapidos y seguros, EI nivel de nitr6geno en forma de nitrato de Lycopersicon esculentum 'Celebrity' fue vigilado en un estudio de invernadero usando laminas de nitrato de ensayo rapido "Merkoquant" para determinar los efectos de variaci6n entre plantas y la variaci6n en posicion de hoj y tiempo del dfa sobre los niveles de nitrato encontrados en la savia del peciolo. Los niveles de nitrato bajaron de 2800 ppm en plantas de 28 dras de edad a menos de 400 ppm en plantas mayores de 68 d(as de edad. Las concentraciones de nitrate en la savia eran iguales en la parte superior, la parte intermediana y la parte mas baja de plantas de 28 dias de edad, peru deerecieron mas rapido en la parte superior de las plantas mientras estas se desarrollaron. Resultados del analisis de tejidos y de la savia concurrieron que la disponibilidad de nitr6geno limitaba el crecimiento. No se noto ninguna diferencia en la concentraci6n de nitrato en la savia entre 10 a.m., 12 p.m. y 2 p.m

Inbreeding depression in male traits and preference for outbred males in Poecilia reticulata

Inbreeding depression often affects male reproductive traits. Here, we measure inbreeding depression in sperm, body size, ornamental color patterns, and attractiveness in male guppies and ask whether different environmental conditions play a role in the severity of inbreeding depression. Male sperm traits and coloration were measured in inbred and outbred fish in 2 experiments under different environmental conditions (large mixed-sex greenhouse tanks and small individual laboratory tanks). Overall, we found that inbreeding leads to significant declines in sperm numbers. Moreover, males raised under greenhouse conditions showed a much stronger decline in sperm numbers with inbreeding compared with those raised under laboratory conditions. These differences might have been caused by a more competitive environment in the greenhouse. The decline in total sperm numbers with inbreeding was due to declining numbers of sperm bundles (spermiozeugmata), not to variation in numbers of spermatozoa within spermiozeugmata. Some, but not all ornamental traits including tail size and the areas of solid black as well as iridescent coloration, were significantly influenced by inbreeding, whereas the environment only affected differences in body size. Mating trials conducted on laboratory-raised fish revealed significantly greater attractiveness of outbred than inbred males. Female choice of outbred over inbred mates may yield direct benefits in the form of greater fertilization efficiency. Copyright 2010, Oxford University Press.