The Interactive Effects of Chilling, Photoperiod, and Forcing Temperature on Flowering Phenology of Temperate Woody Plants

Abstract

The effects of winter chilling, spring forcing temperature, and photoperiod on spring phenology are well known for many European and North American species, but the environmental cues that regulate the spring phenology of East Asian species have not yet been thoroughly investigated. Here, we conducted a growth chamber experiment to test the effects of chilling (controlled by different lengths of exposure to natural chilling conditions), forcing temperature (12, 15, or 18°C) and photoperiod (14 or 10 h) on first flowering date (FFD) of six woody species (three shrubs and three trees) native to East Asia. The three-way analysis of variance (ANOVA) separately for each species showed that the effects of chilling and forcing temperature were significant for almost all species (P < 0.05). Averaged over all chilling and photoperiod treatments, the number of days until FFD decreased by 2.3-36.1 days when the forcing temperature increased by 3°C. More chilling days reduced the time to FFD by 0.7-26 days, when averaged over forcing and photoperiod treatments. A longer photoperiod could advance the FFD by 1.0-5.6 days, on average, but its effect was only significant for two species (including one tree and one shrub). The effects of forcing temperature and photoperiod interacted with chilling for half of the studied species, being stronger in the low chilling than high chilling treatment. These results could be explained by the theory and model of growing degree-days (GDD). Increased exposure to chilling coupled to a longer photoperiod reduced the GDD requirement for FFD, especially when plants grew under low chilling conditions. However, shrubs (except Viburnum dilatatum) had lower chilling and heat requirements than trees, suggesting that, by leafing out sooner, they engage in a more opportunistic life strategy to maximize their growing season, especially before canopy closure from trees' foliage. Our results confirmed the varying effects of these three cues on the flowering phenology of woody species native to East Asia. In future climate change scenarios, spring warming is likely to advance the spring phenology of those woody species, although the reduced chilling and shorter photoperiod may partly offset this spring warming effect.

Establishing the twig method for investigations on pollen characteristics of allergenic tree species

“…In comparison to the outdoor conditions (average temperature 3.7 °C), a much earlier flowering was observed in the climate chamber (average temperature 16.8 °C) for hazel (−69 days), alder (−35 days), and birch (−15 days), ordered by their harvesting dates beginning of December, end of January, and beginning of March. Wang et al ( 2020 ) observed similar trends in a climate chamber experiment on branches of six Asian woody species, where a 3 °C increase in spring temperature resulted in flowering advanced by 2.3 to 36.1 days, depending on the species. In the present study, an impact of the flowering time could be observed on the pollen amount produced, and on pollen characteristics for all investigated species.…”

“…From the literature, it is known that under warmer spring temperatures, flowering is generally accelerated (Fu et al 2012 ; Wang et al 2020 ). In the study of Fu et al ( 2012 ), potted saplings from beech, birch, and oak were treated with various temperature manipulations in climate chambers.…”

Does Climate Warming Favour Early Season Species?

“…There is increasing interest in the role of photoperiod on spring phenology ( Körner and Basler, 2010 ; Polgar and Primack, 2011 ; Way and Montgomery, 2015 ). However, the effects of photoperiod are variable ( Cooke et al, 2012 ; Wang et al, 2020 ) and certainly not as important as temperatures ( Laube et al, 2014 ; Harrington and Gould, 2015 ; Nanninga et al, 2017 ). The claimed photoperiod effects are often confounded with temperature effects, i.e., longer photoperiods are associated with greater forcing temperatures ( Nienstaedt, 1967 ; Worrall and Mergen, 1967 ; Falusi and Calamassi, 1990 ; Heide, 1993 ; Caffarra and Donnelly, 2011 ).…”

Genome-wide signatures in flax pinpoint to adaptive evolution along its ecological gradient

“…This was justified because of the high correlation between them but, as such, their effects ended up being confounded. Plants' mechanisms of recognition of the photoperiod and temperature environmental cues can differ [95][96][97] but there is mounting evidence of complex interactions among them. Indeed, photoperiod sensitivity genes that may trigger flowering response can be intricately-linked to temperature shifts, such as in winter wheat, where they work in concert with vernalization (cold response) genes [98].…”