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

Abstract

The plasticity of leaf form and function in European lines of Arabidopsis thaliana was evaluated in ecotypes from Sweden and Italy grown under contrasting (cool versus hot) temperature regimes. Although both ecotypes exhibited acclimatory adjustments, the Swedish ecotype exhibited more pronounced responses to the two contrasting temperature regimes in several characterized features. These responses included thicker leaves with higher capacities for photosynthesis, likely facilitated by a greater number of phloem cells per minor vein for the active loading and export of sugars, when grown under cool temperature as opposed to leaves with a higher vein density and a greater number of tracheary elements per minor vein, likely facilitating higher rates of transpirational water loss (and thus evaporative cooling), when grown under hot temperature with high water availability. In addition, only the Swedish ecotype exhibited reduced rosette growth and greater levels of foliar tocopherols under the hot growth temperature. These responses, and the greater responsiveness of the Swedish ecotype compared with the Italian ecotype, are discussed in the context of redox signalling networks and transcription factors, and the greater range of environmental conditions experienced by the Swedish versus the Italian ecotype during the growing season in their native habitats.

Light, temperature and tocopherol status influence foliar vascular anatomy and leaf function in Arabidopsis thaliana

“…In particular, this study builds on our previous report (Stewart et al ) that photosynthesis and transpiration, as well as foliar phloem and xylem, undergo differential acclimation to growth temperature in the winter annual A. thaliana . Unlike summer annuals, winter annuals upregulate photosynthetic capacity under cool temperatures (Holaday et al , Adams et al , , , , Martindale and Leegood , Strand et al ).…”

“…Col‐0 and vte1 were grown under a 9‐h photoperiod of 400 µmol photons m −2 s −1 and air temperatures of 8 and 35°C (as temperatures previously shown to elicit contrasting acclimatory responses in this species; Adams et al , Stewart et al ) during the photoperiod (resulting in leaf temperatures of 14°C [cool temperature, CT] and 36°C [hot temperature, HT]; nighttime air and leaf temperatures were 12.5°C and 25°C, respectively) as described in Cohu et al (). After germination and growth under a 25/20°C light/dark air temperature regime for 1 week, plants were transferred to the HT growth regime or, for the CT plants, to an intermediate temperature regime for 1 week [15/15°C (light/dark air temperature)] before transfer to the final temperature regime listed above.…”

“…Leaf function was characterized under common measurement conditions since our detailed previous characterizations of leaves with different vascular anatomies revealed the most highly significant positive correlations between photosynthetic capacity and phloem anatomy under common measurement conditions (Adams et al , Cohu et al ). Measurements of photosynthetic capacity (light‐ and CO 2 ‐saturated rate of oxygen evolution at 25°C) and transpirational water loss were conducted as described in detail previously (Stewart et al , ). Prior to measurement of transpiration, plants were removed from the growth chamber approximately 5 h into the photoperiod, and leaves were exposed to 100 (LL plants), 400 (CT and HT plants) or 1000 (HL plants) µmol photons m −2 s −1 for 5 min in air with a mean vapor pressure deficit of 2.39 ± 0.41 kPa at a mean leaf temperature of 27.8 ± 1.8°C and CO 2 concentrations of 460 ± 56 ppm (± standard deviation; n = 35 for each mean).…”

“…The leaf's lamina is supported by the major veins that scale with leaf size (Sack et al ), while the smaller vein classes (minor foliar veins) serve mainly in the exchange of water and sugar. We previously reported that the foliar minor vein network of the model species Arabidopsis thaliana (a winter annual) exhibits adjustments in response to plant growth environment, and that significant positive correlations exist between photosynthetic capacity and various phloem features (Adams et al , , , Cohu et al , , , Stewart et al ). Arabidopsis thaliana did not, however, exhibit consistent associations between photosynthetic capacity and xylem features (Cohu et al ; see Adams et al for further explanation).…”

“…Unlike summer annuals, winter annuals upregulate photosynthetic capacity under cool temperatures (Holaday et al , Adams et al , , , , Martindale and Leegood , Strand et al ). Stewart et al () showed that higher photosynthetic capacities in cool‐grown vs hot‐grown A. thaliana ecotypes from Sweden and Italy were associated with greater numbers of phloem cells in foliar veins, and that the lower transpiration rates in these cool‐grown plants were associated with fewer xylem cells in foliar veins when compared with hot‐grown plants (see also Adams et al ). These observations are consistent with reports of greater phloem‐to‐xylem ratios in cold‐grown leaves of spring and winter wheat (Equiza and Tognetti ) and in the vasculature of carrot root (González et al ).…”