The Effects of Photoperiod on Flower-bud Development in Phaseolus vulgaris

For a variety of Phaseolus vulgaris of Peruvian origin, extendingthe daylength from 11 to 15 or 16 h with low-intensity incandescentor natural light, while not affecting the rate of initiationof flower primordia, inhibited the development of the flowerbuds and caused many, and sometimes all of them, to senesceand abscise. The inhibition of the oldest flower bud was firstdetected at the stage of pollen formation. The long photoperiodsalso inhibited the elongation and over-all development of theterminal inflorescence but, in contrast, promoted the elongationof those internodes below the first trifoliate leaf and alsothe elongation of the petioles.     

Growth and oviposition of the freshwater pulmonate Bulinns tropicus (Gastropoda) reared in the laboratory under reversed, extreme and irregular ultradian light-dark cycles

The effect of irregular photoperiods on various growth parameters and oviposition of a tropical freshwater pulmonate, Bulinus tropicus , has been investigated. Over a period of 6 weeks the growth (measured as an increase in wet weight) of juvenile snails was unaffected by transfer to reversed and to random non-circadian light-dark regimens, although oviposition was considerably retarded in the latter experimental group and its time of onset was delayed relative to the control group held in a 12 h light-12 h dark regimen. Snails exposed to constant light grew more, and their oviposition rate (number of eggs snail^-1 week^-1) was equal to that of the control group, but these two parameters were found to be considerably reduced in snails kept in constant darkness. The food consumption, assimilation and food conversion efficiency of snails in random and reversed light-dark regimens were comparable to the control groups, whereas animals in constant light ate more and those in constant darkness ate less. The weekly mean assimilation rate and food conversion efficiency were greater in the latter group, however.     

The influence of temperature on nest site choice and reproductive strategy in a temperate zone Polistes wasp

Abstract. 1. Field experiments with Polistes fuscutus showed that more nests were initiated, co-foundress groups were larger, broods developed faster, and workers eclosed earlier in sun-warmed sites than in cool ones.
2. These results suggest that colonies nesting in sun-warmed shelters gained a fitness advantage over those in cooler shelters. More rapid brood development means that such colonies reach the ergonomic stage more quickly, which in turn means a higher expectancy of survival and greater productivity at the end of the season.
3. We argue that thermal properties constitute an important component of Polistes nest site quality in temperate regions and that these properties influence joining and usurping strategies as well as nest site choice in spring Polistes females. Other factors being equal, a joining or usurping female should opt for a colony in a warm site over one in a cool site, leading to the larger foundress groups we found in warm shelters.
4. We hypothesize that the selective advantage of philopatry in temperate zone Polistes populations is that it brings spring females to nest sites of proven quality.