Drought limits foliar water uptake in C3 perennial grasses

Rain, fog, and dew can all provide the conditions necessary to induce direct uptake of water into the foliage of plants. Although grasslands are known to have frequent leaf-wetting events, the capacity of grasses to conduct foliar water uptake has never been explicitly quantified. Here, we show the results of greenhouse experiments used to quantify foliar water uptake during leaf wetting and characterize the importance of foliar water uptake during drought. Across the species tested, we found an average foliar water uptake of 3.34 ± 0.32 [mg H2O cm-2] which represented a leaf water content increase of 8.82 ± 0.95 % over a three-hour leaf wetting treatment. We show that leaves with higher wettability exhibit lower resistance to foliar water uptake, consistent with previous theory. Our results indicate that foliar water uptake occurs in C3 perennial grasses and can provide relief during drought. However, we found that the benefits resulting from foliar water uptake decrease as drought becomes severe and plants close their stomata to conserve water.