Growth and ethylene evolution by shade and sun ecotypes of Stellaria longipes in response to varied light quality and irradiance

Abstract

Plants growing in the shade receive both low light irradiance and light enriched in far red (FR) (i.e. light with a low red (R) to FR ratio). In an attempt to uncouple the R/FR ratio effects from light irradiance effects, we utilized Stellaria longipes because this species has two distinct natural population ecotypes, alpine (dwarf) and prairie (tall). The alpine population occupies the open, sun habitat. By contrast, the prairie population grows in the shade of other plants. Both 'sun' and 'shade' ecotypes responded with increased stem elongation responses under low irradiance, relative to growth under 'normal' irradiance, and this increased growth was proportionally similar. However, only the shade ecotype had increased shoot elongation in response to a low R/FR ratio. By contrast, the sun ecotype showed increased stem elongation in response to increasing R/FR ratio. Varying the R/FR ratios had no significant effect on ethylene evolution in either sun or shade ecotype. Under low irradiance, only the sun ecotype showed a significantly changed (decreased) ethylene evolution. We conclude that R/FR ratio and irradiance both regulate growth, and that irradiance can also influence ethylene evolution of the sun ecotype. By contrast, R/FR ratio and irradiance, while having profound influences on growth of the shade ecotype, do not appear to regulate these growth changes via effects on ethylene production.

The roles and interactions of ethylene with gibberellins in the far-red enriched light-mediated growth of Solanum lycopersicum seedlings

“…Therefore, various plant species may have adapted differently in utilizing ethylene under shade light. Similar results were shown in the studies with the Stellaria longipes complex, where sun and shade ecotypes were characterized (Emery et al 1994a) and the role of ethylene in their growth has been well established (Emery et al 1994b;Kurepin et al 2006c;Walton et al 2006). When these ecotypes were tested under varying light irradiance levels, the sun (but not shade) ecotype plants had reduced ethylene levels under low light irradiance (Kurepin et al 2007a).…”

The Regulation of Cell Wall Extensibility during Shade Avoidance: A Study Using Two Contrasting Ecotypes of Stellaria longipes

“…In response to the same light signal, there is again a difference between ecotypes in the identity of the expansin expressed. Previous studies with the alpine and prairie ecotypes of S. longipes implicated the hormones ethylene and gibberellin in the observed differential responses to shade (Kurepin et al, 2006a(Kurepin et al, , 2006b). Phytohormones have a good potential to regulate the amount of plasticity in response to environmental cues.…”

“…Phytohormones have a good potential to regulate the amount of plasticity in response to environmental cues. The two ecotypes of S. longipes clearly show different levels of, and sensitivities to, these hormones (Kurepin et al, 2006a(Kurepin et al, , 2006b). Cell wall-modifying proteins like expansins and XTHs may very well be the downstream targets of these hormones, allowing control of the timing and magnitude of the elongation response.…”

Narrow-band light regulation of ethylene and gibberellin levels in hydroponically-grown Helianthus annuus hypocotyls and roots

“…0.2 g fresh weight tissue in a 3 mL syringe (1.5 mL volume) for 15 min. A 1 mL gas sample was collected and injected into a Photovac 10Splus GC (Photovac Inc., Markham, Ontario) with a photoionization detector and a 40/60 Carbopack B column (Supelco Canada, Oakville, Ontario), as described in Kurepin et al (2006b).…”