The testicular growth of guinea-fowls in relation to age was compared under 3 constant photoperiods (7L: 17D; 14L: 10D; 20L: 4D) from 3 weeks of age. Although long daylength (14L or 20L) caused precocious development of the gonads, it also limited total adult gonadal weight to around 1 800 +/- 200 mg. Short daylengths (7L) delayed the development of the gonads but their adult weight was enhance...

The response to daylength is a crucial process that evolved very early in plant evolution, entitling the early green eukaryote to predict seasonal variability and attune its physiological responses to the environment. The photoperiod responses evolved into the complex signaling pathways that govern the angiosperm floral transition today. The Chlamydomonas reinhardtii DNA-Binding with One Finger...

The highly conserved florigen gene FLOWERING LOCUS T (FT) functions at the core of the flowering pathways. Extensive studies have examined the transcriptional regulation of FT; however, other layers of FT regulation remain unclear. Here, we identified miR5200 a Pooideae-specific microRNA that is expressed in leaves and targets Brachypodium distachyon FT orthologs for mRNA cleavage. miR5200 was ...

A major question in chronobiology focuses around the "Bünning hypothesis" which implicates the circadian clock in photoperiodic (day-length) measurement and is supported in some systems (e.g. plants) but disputed in others. Here, we used the seasonally-regulated thermotolerance of Drosophila melanogaster to test the role of various clock genes in day-length measurement. In Drosophila, freezing ...

Evidence for a role of the pineal gland and its major hormonal product, melatonin, in mammalian reproduction has accumulated for over three decades. In sorting through the masses of data pertaining to this issue, certain facts are becoming established. For example, the pineal gland is clearly involved in seasonal reproductive cycles via transduction of daylength (more properly nightlength) info...

The flowering time of plants is tightly regulated by both promotive and repressive factors. Molecular genetic studies using Arabidopsis have identified several epigenetic repressors that regulate flowering time. Terminal flower2, (TFL2), which encodes a homolog of heterochromatin protein1 represses flowering locus T (FT) expression, which is induced by the activator constans (CO) in response to...

The morphogenetic changes of the bud meristem during floral initiation in gooseberry were examined by scanning electron microscopy. Six stages, similar to those reported for black currants, identified. We also studied environmental control shoot growth and cvs. Mucurines, Pax Xenia two experiments daylight phytotron compartments at 12, 18 24°C. Under natural daylength conditions Ås, Norway (69°...

Flowering time in rice (Oryza sativa L.) is determined primarily by daylength (photoperiod), and natural variation in flowering time is due to quantitative trait loci involved in photoperiodic flowering. To date, genetic analysis of natural variants in rice flowering time has resulted in the positional cloning of at least 12 quantitative trait genes (QTGs), including our recently cloned QTGs, H...