LAUSR

Abstract The plasticity of plant development allows acclimation to environmental stresses such as heat and drought. For example, increased vein density with more vein meetings is proposed to provide more efficient and robust water delivery when water availability is reduced. We demonstrate that Arabidopsis leaves respond to short term heat or drought by increasing leaf vein density, which in heat includes a higher density of vein meetings. We find that a set of genes, UNHINGED, FORKED1, FORKED-LIKE1, 2 and 3, which influence PINFORMED1 localization and control vein meeting in developing leaves, is required for the vein pattern response to heat or drought. Comparison of δ13C (‰) and nitrogen (%) under different conditions suggests that while wild type and mutant genotypes enriched δ13C (‰) under drought conditions, only wild type increased total shoot nitrogen suggesting increased photosynthetic assimilation. One explanation is that the mutants’ open vein pattern fails to supply sufficient water to support increased photosynthesis. Finally, treatment with ABA caused changes to leaf vein pattern similar to heat or drought treatment, a response that was eliminated in the abscisic acid insensitive1 but not the forked1 genotype. This suggests that the vein pattern response to reduced water availability may in part be controlled by ABA.