Varietal Responses to Temperature in Swedes

Four swede varieties and their six F¹ hybrids were grown (for42 d) at different temperatures and also (for 32 d) under differentsoil and air temperature regimes. The weights of the F¹ hybridswere either intermediate to or resembled those of their parents.The varieties appeared to require a 10 °C difference betweenair and soil temperatures for optimal growth. The variety withthe lowest plant weight was Wilby and at low light intensityand under constant air and soil temperature this variety died.All varieties benefited by reduced soil or air temperature althoughthey varied in their optimal requirements. The results indicatedthat temperature x varietal interaction effects might have considerableimportance in the utilization of existing varieties or in thebreeding of new ones.     

Morphological convergence during pregnancy among predator and nonpredator populations of the livebearing fish Brachyrhaphis rhabdophora (Teleostei: Poeciliidae)

Predation can drive morphological divergence in prey populations, although examples of divergent selection are typically limited to nonreproductive individuals. In livebearing females, shape often changes drastically during pregnancy, reducing speed and mobility and enhancing susceptibility to predation. In the present study, we document morphological divergence among populations of nonreproductive female livebearing fish (Brachyrhaphis rhabdophora) in predator and nonpredator environments. We then test the hypothesis that shape differences among nonreproductive females are maintained among reproductive females between predator and nonpredator environments. Nonreproductive females in predator environments had larger caudal regions and more fusiform bodies than females in nonpredator environments; traits that are associated with burst speed in fish. Shape differences were maintained in reproductive females, although the magnitude of this difference declined relative to nonreproductive females, suggesting morphological convergence during pregnancy. Phenotypic change vector analysis revealed that females in predator environments became more similar to females in nonpredator environments in the transition from nonreproductive to reproductive. Furthermore, the level of reproductive allocation affected shape similarly between predator environments. These results suggest a life‐history constraint on morphology, in which predator‐driven morphological divergence among nonreproductive B. rhabdophora is not maintained at the same level during pregnancy. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 386–392.     

Mechanism of Action of Luteinizing Hormone

WE have reported¹ studies on luteinized rat ovary in which we found that an approximate doubling of the rate of steroid synthesis following stimulation with luteinizing hormone was not associated with any change in the tissue NADPH/NADP⁺ concentration ratio. We concluded that it was unlikely that luteinizing hormone brought about the increase in steroid synthesis solely by increasing the production of NADPH by glucose 6-phosphate dehydrogenase or another cytoplasmic NADPH-linked dehydrogenase, as had been suggested^2,3.