Premise of study: Leaf shape is predicted to have important ecophysiological consequences; for example, theory predicts that lobed leaves should track air temperature more closely than their entire-margined counterparts. Hence, leaf-lobing may be advantageous during cold nights (∼0°C) when there is the risk of damage by radiation frost (a phenomenon whereby leaves fall below air temperature because of an imbalance between radiational heat loss and convective heat gain). Methods: Here, we test whether radiation frost can lead to differential damage between leaf shapes by examining a leaf-shape polymorphism in Ipomoea hederacea, where leaves are either lobed or heart-shaped depending on a single Mendelian locus. We logged leaf temperature during midautumn, and measured chlorophyll fluorescence and survival as proxies of performance. Furthermore, we tested if the leaf-shape locus confers freezing tolerance using freezing assays on leaf tissue from different leaf shapes. Key results: We found that lobed leaves consistently remain warmer than heart-shaped leaves during the night, but that no pattern emerged during the day, and that temperature differences between leaf shapes were typically small. Furthermore, we found that leaf types did not differ in frost tolerance, but that a 1°C decrease leads to a transition from moderate to complete damage. Conclusions: Our results demonstrate that Ipomoea hederacea leaf shapes do experience different nighttime temperatures, and that only minor temperature differences can lead to disparate levels of freezing damage, suggesting that the differential thermoregulation could result in different levels of frost damage.
Usage Notes:
Campitelli et al 2013 - Rooftop Leaf temperature
Raw leaf temperature data for the rooftop experiment. The column headers (Lobe, Heart, Hetero) refer to the three leaf shape genotypes outlined in the paper.
Campitelli et al 2013 - Rooftop Fv_Fm & Survival
Raw data for photosynthetic efficiency (FV/FM) for each plant in the rooftop experiment, as described in the paper. For any given plant, if FV/FM is missing ("."), this indicates that plant has died; hence, this data can also be used to estimate the time length of survival for each plant.
Campitelli et al 2013 - Relative Conductivity Non-acclimated plants
Relative conductivity values (estimated as described in the paper) for non-acclimated plant tissue. These data correspond to the "Freezing tolerance of non-acclimated tissue" experiment, described in the paper.
Campitelli et al 2013 - Relative Conductivity Acclimated plants
Relative conductivity values of acclimated plant tissue, calculated as described in the paper. These data correspond to the "Freezing tolerance of cold-hardened tissue" experiment described in the paper