Differences in light-harvesting, acclimation to growth-light environment, and leaf structural development between Swedish and Italian ecotypes of Arabidopsis thaliana

Abstract

Leaf morphological differences have an impact on light distribution within the leaf, photosynthesis, and photoprotection in Arabidopsis thaliana ecotypes from near the limits of this species' latitudinal distribution in Europe. Leaf morphology, photosynthesis, and photoprotection were characterized in two Arabidopsis ecotypes from near the limits of this species' latitudinal distribution in Europe (63°N and 42°N). The Swedish ecotype formed thicker leaves and upregulated photosynthesis more substantially than the Italian ecotype in high-light environments. Conversely, the smaller rosette formed, and lesser aboveground biomass accumulated, by the Swedish versus the Italian ecotype in low growth-light environments is consistent with a lesser shade tolerance of the Swedish ecotype. The response of the thinner leaves of the Italian ecotype to evenly spaced daily periods of higher light against a background of otherwise non-fluctuating low light was to perform the same rate of photosynthesis with less chlorophyll, rather than exhibiting greater rates of photosynthesis. In contrast, the thicker leaves of the Swedish ecotype showed elevated photosynthetic performance in response to daily supplemental higher light periods in a low-light growth environment. These findings suggest significant self-shading in the lower depths of leaves of the Swedish ecotype by the chloroplasts residing in the upper portions of the leaf, resulting in a requirement for higher incident light to trigger photosynthetic upregulation in the lower portions of its thicker leaves. Conversely, photoprotective responses in the Italian ecotype suggest that more excess light penetrated into the lower depths of this ecotype's leaves. It is speculated that light absorption and the degree of utilization of this absorbed light inform cellular signaling networks that orchestrate leaf structural development, which, in turn, affects light distribution and the level of absorbed versus photosynthetically utilized light in a leaf.

Growth temperature impact on leaf form and function in Arabidopsis thaliana ecotypes from northern and southern Europe

“…); for a discussion of the impact of reference basis for the expression of photosynthesis rates, see Stewart et al . () and Dahal et al . ().…”

“…A greater responsiveness of the Swedish compared with the Italian ecotype was also noted previously when the plants were grown in a fluctuating light environment (Stewart et al . ) and for photosynthetic capacity and vascular architecture of foliar minor veins in response to growth under low compared with moderate temperature (Cohu et al . ,).…”

“…); for further details on these sites and ecotype performance, see Ågren & Schemske () and the Discussion, and for details on the lines utilized in the present study, see Stewart et al . (). For all measurements, three to five non‐flowering plants from each ecotype and each growth temperature were evaluated.…”

“…) within 24 h of harvest using a Canon digital camera (EOS Rebel Series, Canon USA Inc, Melville, New York, USA) as described in Stewart et al . (). In a subsequent experiment, both ecotypes were grown under the high temperature regime in order to evaluate changes in rosette size over time ( n = 5 plants per ecotype).…”

“…Extraction of chlorophylls and tocopherols (from three to five leaf discs from three to five plants) followed by quantification using high‐performance liquid chromatography was as described in Stewart et al . ().…”