Light and photoperiod are environmental signals that regulate flowering transition. In plants like Arabidopsis thaliana, this regulation relies on CONSTANS, a transcription factor that is negatively posttranslational regulated by phytochrome B during the morning, while it is stabilized by PHYA and cryptochromes 1/2 at the end of daylight hours. CO induces the expression of FT, whose protein travels from the leaves to the apical meristem, where it binds to FD to regulate some flowering genes. Although PHYB delays flowering, we show that light and PHYB positively regulate XAANTAL1 and other flowering genes in the shoot apices. Also, the genetic data indicate that XAL1 and FD participate in the same signaling pathway in flowering promotion when plants are grown under a long-day photoperiod at 22 °C. By contrast, XAL1 functions independently of FD or PIF4 to induce flowering at higher temperatures (27 °C), even under long days. Furthermore, XAL1 directly binds to FD, SOC1, LFY, and AP1 promoters. Our findings lead us to propose that light and temperature influence the floral network at the meristem level in a partially independent way of the signaling generated from the leaves.

We have obtained uvby − β photoelectric photometry with the 0.84 m telescope at the San Pedro Mártir Observatory, México, for the stars HD 115520, HD 220735 and HD 26738. The first two had been previously determined to be variables whereas the last one is being reported here as a new variable. With an extended time basis for the first two, we have determined their period of pulsation, which is found to be stable. Physical parameters are presented for the three stars.

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We determine the nature of the Delta Scuti star AD CMi and its physical parameters from newly determined times of maximum light and other times from the literature, as well as from uvby −β photoelectric photometry.