Effects of temperature on the growth of spring ephemerals: Crocus vernus

Abstract

Spring ephemerals of deciduous forests appear shortly after snow melt and senesce shortly after the overstorey canopy has closed. During this short period, they take advantage of the high light conditions, but also of the low‐temperature regime that favours growth in these species. This better growth at cooler temperatures has been attributed to longer leaf life duration. The objective of this study was to test if temperature effect on growth in spring ephemerals can be explained solely by the leaf life duration, or if there is also a direct temperature effect on the underground organ growth. Crocus vernus (L.) Hill was exposed to two temperature regimes, 12/8 and 18/14°C (day/night), for sequential harvests and to four differential air to soil temperature regimes: 12/12, 12/18, 18/12 and 18/18°C (air/soil temperature). Dry mass, leaf nitrogen, starch concentration and cell size of the new corm were determined. Final dry mass and cell size were higher at the lower temperature regime while leaf lasted longer than at the higher temperature regime. Although both air and soil temperatures had an impact on the different growth parameters measured, the impact of soil temperatures was greater and it also influenced leaf life duration. At higher temperature, corm growth stopped before the first visual sign of leaf senescence, suggesting that corm growth controls leaf life duration in C. vernus rather than the opposite and that crocus growth becomes rapidly sink limited at higher temperatures.

Effects of growth temperature and winter duration on leaf phenology of a spring ephemeral (Gagea lutea) and a summergreen forb (Maianthemum dilatatum)

“…The decrease in the mature and senescent periods in the leaves of G. lutea in this study and E. japonicum (Yoshie and Fukuda 1994) at warm temperatures is caused by an activation of metabolic processes of the rate of aging, resulting from either a direct effect of temperature or from an indirect effect through a reduction in the sink demand as suggested by Lapointe (2001). At higher cultivation temperature corm growth of Crocus vernus stopped before the first visual sign of leaf senescence, suggesting that corm growth controls leaf longevity rather than the opposite and that growth becomes rapidly sink limited (Badri et al 2007).…”

“…Warm air temperatures shorten the leaf longevity in Crocus vernus (Badri et al 2007) and tulips (Rees 1972). The plastic responses of summer dormancy in these plants ensure their ability to avoid hot and dry summers.…”

How do sink and source activities influence the reproduction and vegetative growth of spring ephemeral herbs under different light conditions?

“…Previous studies demonstrated that vegetative growth of spring ephemerals was terminated by the increase in soil temperature because warm temperature activated the metabolic process of aging (Badri et al 2007;Yoshie 2008). These studies suggest that growing season length of spring ephemerals may be determined by temperature regime but not by light environment.…”

Aging in Perennials

“…Spring ephemerals are well adapted to the high light conditions prevailing during early spring before trees leaf out but also to the low temperature conditions of that period. Not only do they tolerate cold temperatures, but they actually grow better under such low temperature regime and produce a larger perennial organ (Badri et al, 2007). Few studies have, however, examined the age structure of populations of spring ephemerals.…”