abstract increased knowledge of russian knapweed biology would facilitate development of an optimum control program. to examine germination characteristic of this weed, several experiments were conducted in weed research department, plant pest and diseases research institute of tehran during 2003. first experiment was a factorial with 3 replications to break seed dormancy of this weed. first fa...

Carex divisa is a patrimonial rhizomatous species and acts as an important component of grazed wet permanent grassland on the French Atlantic coast. This study treated three storage regimes (wet-cold, dry-cold and dry-warm), burial in soil, fluctuating temperature and salinity on seed germination of C. divisa. The seeds were dormant at maturity. No seed germinated after 2 and 6 weeks of dry sto...

Ectotherms commonly adjust storage and membrane lipid composition to ambient temperature to counteract detrimental thermal effects on lipid fluidity. The effect of repeated temperature fluctuations on fatty acid composition and thermal tolerance was investigated. We exposed Orchesella cincta to two constant temperatures (5ºC and 20°C), and a continuously fluctuating treatment (5ºC/20ºC every tw...

Cold storage is a valuable method for reducing the cost of producing large amounts of biological agents. Fluctuating thermal regimes (prolonged exposures at low temperatures combined with periodic short higher temperature) are reported to improve cold survival and fecundity in some parasitoid species. In this study, the pupal stage of the parasitoid wasp Lysiphlebus fabarum (Marshall) (Braconid...

Natural environments are characterized by daily and seasonal fluctuations in temperature, and ectotherms are expected to adapt to these fluctuations. Moderate temperature fluctuations often accelerate development rate as a result of the Kaufmann effect and possibly additional physiological adaptations. We examined the adaptive potential of ecotype-specific reaction norms by measuring the effect...

Most terrestrial ectotherms experience diurnal and seasonal variation in temperature. Because thermal performance curves are non-linear, mean performance can differ in fluctuating and constant thermal environments. However, time-dependent effects--effects of the order and duration of exposure to temperature--can also influence mean performance. We quantified the non-linear and time-dependent ef...

The Maxwell distribution is derived from the F -distribution in the limit where one of the degrees of freedom of the χ variates tends to infinity. The estimator of the temperature is consistent, and, hence coincides with the temperature of the heat reservoir in the asymptotic limit; it is also unbiased and efficient. Consequently, there is a contradiction between indentifying the Lagrange multi...

Our understanding of how oxidative stress resistance phenotypes are affected by the developmental environment is limited. One component of the developmental environment, which is likely central to early life oxidative stress among ectothermic and oviparous species, is that of temperature. We investigated how incubation temperature manipulations affect oxidative damage and total antioxidant capa...