The Spatial Distribution of Chloroplast Water in Acer plantanoides Sun and Shade Leaves

We evaluated a new, two‐dimensional (2‐D) nuclear magnetic resonance (NMR) imaging technique as a method for measuring the distribution of chloroplasts in leaves. NMR images that showed the distribution of chloroplast water and of total water as a function of depth into Acer platanoides sun and shade leaves were compared with the distribution of chlorophyll in the same leaf types (as measured by fluorescence microscopy), with the cellular structure (by scanning electron microscopy), and with published information. Results showed that the volume fraction of chloroplast water was much larger in shade than in sun leaves, and that it averaged about one‐third larger in the palisade than in the spongy parenchyma region of both leaf types. Chlorophyll fluorescence was more intense in shade than in sun leaves. In sun leaves, fluorescence was maximal in the palisade region near the junction with the spongy parenchyma, while in shade leaves, fluorescence was maximal in the upper part of the spongy layer. We concluded that 2‐D NMR imaging reliably indicates the location of chloroplast water