Cooler temperatures favour growth of wild leek (Allium tricoccum), a deciduous forest spring ephemeral

Abstract

Allium tricoccum Aiton is a common spring ephemeral of hardwood deciduous forests of northeastern North America. It takes advantage of the short period of high light conditions between snowmelt and canopy closure to complete its vegetative life cycle and accumulate carbohydrate reserves for the following year. Previous studies on other spring ephemerals have shown that growth of these species is enhanced when grown at low temperature, typical of very early spring. We thus quantified the effect of three growth temperature regimes, i.e., 18 °C day – 14 °C night, 12 °C day – 8 °C night, and 8 °C day – 6 °C night, which have previously been tested on Erythronium americanum, another spring ephemeral. Gas exchange, chlorophyll a fluorescence, and plant biomass were measured repeatedly throughout the growth season. Growth was greatest under the 12 °C day – 8 °C night temperature regime, consistent with enhanced net photosynthetic rates (Pn), photochemical quenching (qP), and photochemical efficiency of photosynthesis (ΦPSII) at this temperature regime throughout the season. Pn was similar at 18 °C day – 14 °C night and 8 °C day – 6 °C night, but leaves had a greater duration at 8 °C day – 6 °C night; however, bulb biomass was not greater at 8 °C day – 6 °C night than at 18 °C day – 14 °C night. This study corroborates the general sensitivity of spring ephemerals to warmer temperatures. It also highlights species differences that might be caused by their specific carbon metabolism at the bulb level.