Bulb growth potential is independent of leaf longevity for the spring ephemeralErythronium americanumKer-Gawl.

Abstract

Growth in most spring ephemerals is decreased under warmer temperatures. Although photosynthetic activities are improved at warmer temperatures, leaves senesce earlier, which prevents the bulb from reaching a larger size. A longer leaf life duration during a warm spring, therefore, may improve bulb mass. We tested this hypothesis by modulating leaf life span of Erythronium americanum through the application of Promalin® (PRO; cytokinins and gibberellins) that prolonged, or silver thiosulphate (STS) that reduced leaf duration. Gas exchange and chlorophyll fluorescence were measured along with leaf and bulb carbohydrate concentrations. Plants were also pulse labelled with 13CO2 to monitor sugar transport to the bulb. Lower photosynthetic rates and shorter leaf life span of STS plants reduced the quantity of C that they assimilated during the season, resulting in a smaller bulb compared to Control plants. PRO plants maintained their photosynthetic rates for a longer period than Control plants, yet final bulb biomass did not differ between them. We conclude that seasonal growth for E. americanum is not limited by leaf life duration under warm growing conditions, but rather by limited sink growth capacity. Under global warming, spring geophytes might be at risk of being reduced in size and eventually, reproducing less frequently.

Interannual variation in spring weather conditions as a driver of spring wildflower coverage: a 15-year perspective from an old-growth temperate forest

“…Focusing on a trait that is documented as spanning several growing seasons uncovered the influence that previous-year conditions can have on these ephemerals. Regardless of trait, short-term studies like Nault and Gagnon’s (1993) all agree that cooler temperatures benefit spring ephemerals ( Routhier and Lapointe 2002 ; Lundmark et al 2009 ; Gandin et al 2011 ; Kim et al 2015 ; Sunmonu and Kudo 2015 ; Dion et al 2017 ; Bertrand and Lapointe 2022 ). Where they disagree, however, is the reason colder temperatures are beneficial.…”

“…Bulb biomass, leaf longevity and pollen production of G. lutea are also all reduced when grown in warmer spring temperatures ( Sunmonu and Kudo 2015 ). E. americanum does not appear to benefit from delayed leaf senescence, as the plants are unable to accumulate more carbon in their perennial bulb during this extended period ( Bertrand and Lapointe 2022 ). When grown at low temperatures, however, E. americanum plants produce larger perennial bulbs because they are less source-sink imbalanced ( Gandin et al 2011 ).…”

Understanding the effects of weather parameters on the population dynamics of an endangered geophyte supports monitoring efficiency

“…Without the warm -cold -warm temperature sequence, especially without the cold period, certain sugar transport routes are not activated and the development of geophytes cannot be completed (Khodorova et al 2010;Augspurger and Salk 2017). Increased temperature during the assimilation period was found to lead to shorter leaf activity, earlier leaf senescence, and lower bulb yield (Lapointe 2001, Khodorova et al 2010, Gandin et al 2011Bertrand and Lapointe 2023). These changes are also related to altered molecular pathways: increased temperature leads to increased photosynthetic rate in many early owering species, however, cellular growth in storage organs cannot keep up with increasing demand of storage capacity.…”