Light acclimation strategies change from summer green to spring ephemeral as wild‐leek plants age

Abstract

Wild-leek seedlings exhibit a summer-green phenology, whereas mature plants behave as true spring ephemerals. Growth appears to be more source-limited in seedlings than in mature plants. This modulation of phenological strategy, if confirmed in other species, would require a review of the current classification of species as either spring ephemerals, summer greens, wintergreens, or evergreens.

Do UV‐A radiation and blue light during growth prime leaves to cope with acute high light in photoreceptor mutants ofArabidopsis thaliana?

“…Plants experience a dynamic and heterogeneous light environment, where spectral composition and irradiance can change depending upon the time of day, and of year, as well as the surrounding vegetation ( Constabel and Lieffers , Montgomery and Chazdon ). To maintain a positive carbon balance, plants beneath canopies must respond to changes in solar radiation throughout the growing season (Augspurger , Lopez et al , Dion et al ): when reduced irradiance during spring due to canopy closure accompanies differential attenuation of the blue (Casal ; who defines blue as 400–500 nm) and ultraviolet (UV)‐A regions affecting spectral composition in the understorey (Grant et al ). Spring bud burst of deciduous species in temperate and boreal forests results in a reduction in total under‐canopy irradiance (Richardson and O'Keefe ) and a change in its spectral composition: reductions in the R:FR (red:far‐red light ratio defined as 655–665:725–735 nm) and blue:green ratios, as well as an increase in the UV:PAR ratio (UV 280–400: photosynthetically active radiation 400–700 nm) reaching the understorey (Flint and Caldwell , Leuchner et al , Urban et al , Dengel et al ).…”

Late canopy closure delays senescence and promotes growth of the spring ephemeral wild leek (Allium tricoccum)

“…C as a function of total light reaching the plot during the season confirmed that wild leek did acclimate to the light conditions and that mean photosynthetic rates increased with light availability, as would be expected for leaves that are acclimated to higher light conditions (Nobel, 1991). Light acclimation most likely took place following a first growing season under the new growth conditions, as mature wild leek do not acclimate their leaves within a single season (Bernatchez et al, 2013;Dion et al, 2016). This acclimation to light availability could explain the increased bulb size that was reported for plots receiving more light throughout the growing season, along with delayed leaf senescence in these plots.…”

“…One would not expect the growth of a spring ephemeral to be influenced by the amount of light passing through the canopy following its closure. However, we have recently shown that modulating light during leaf senescence in wild leek influences the photosynthetic rates that are recorded in the green sections of the leaf, as well as final bulb size (Dion et al, 2016). The light conditions during leaf senescence can thus influence the total amount of C that is fixed and, therefore, the amount of C that accumulates in the bulb.…”

“…In a recent experiment under controlled light conditions, we demonstrated the positive effect of increased light availability on the growth of the wild leek Allium tricoccum Ait. (Amaryllidaceae; Dion et al, 2016). However, experiments in natural environments involving spring ephemerals, such as wild leek, did not report a clear relationship between their growth rate and light availability prior to canopy closure (Vasseur and Gagnon, 1994;Delagrange et al, 2013).…”

Carbon gain phenologies of spring‐flowering perennials in a deciduous forest indicate a novel niche for a widespread invader

“…Leaf function in understory herbs also shifts seasonally, in ways that are poorly understood across species even within a phenological group (Mahall & Bormann, 1978;Tessier, 2008;Dion et al, 2016). Several studies have included leaf photosynthetic capacities and respiration rates to better characterize shade avoidance (e.g.…”