Young leaves in some plants are transiently red due to the presence of anthocyanins, which disappear upon maturation. We investigated the hypothesis that light attenuation by anthocyanins may lead to a shade acclimation of the photosynthetic machinery in red leaves. We took advantage of the intra-species variation in anthocyanin levels of young, exposed leaves of Quercus coccifera. Thus, photosynthetic and photoprotective characteristics were compared in young green and red leaves of the same age, sampled from the corresponding phenotypes occupying the same habitat. Red leaves displayed several shade attributes like thinner laminae, lower Chl a/b ratios and lower levels of the xanthophyll cycle components and β-carotene. In addition, although both leaf kinds had the same area based levels of chlorophylls, these pigments were excluded from the sub-epidermic anthocyanic cell layers, leading to a further reduction of effective mesophyll thickness and an increase in chlorophyll density. Accordingly, red leaves had higher absolute chlorophyll fluorescence signals. In spite of these apparent shade characters, red leaves were less prone to photoinhibition under mild laboratory conditions and displayed slightly but significantly higher PS II photochemical efficiencies at pre-dawn in the field. No differences in all the above measured parameters were found in mature green leaves of the two phenotypes. The results confirm the light acclimation hypothesis and are also compatible with a photoprotective function of anthocyanins.

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Capparis spinosa (caper), a winter-deciduous perennial shrub, is a consistent floristic element of Mediterranean ecosystems, growing from May to October, i.e. entirely during the prolonged summer drought. The internal architecture of young and fully expanded leaves was studied, along with certain physiological characteristics. Capparis spinosa possesses thick, amphistomatic and homobaric leaves with a multilayered mesophyll. The latter possesses an increased number of photosynthesizing cells per unit leaf surface, a large surface area of mesophyll cells facing intercellular spaces (Smes) and a low percentage of intercellular space per tissue volume. Smes and chlorophyll content attain their maximum values synchronously, slightly before full leaf expansion. Nitrogen investment is also completed before full leaf expansion. The structural features, in combination with the water status, could contribute to enhanced rates of transpiration and photosynthesis under field water shortage conditions.

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Variations in concentration and tissue distribution of mineral elements in seeds of seven quinoa cultivars from both a “natural” habitat (Patacamaya, Bolivia, 3,960 m above sea level) and a “nonnatural” habitat (Encalilla, Argentina, 1,980 m above sea level) were analyzed. Data clearly showed inter‐ and intravarietal differences in seed mineral concentrations between the two sites. Correlation analysis revealed that concentrations of major and minor dietary minerals as well as essential ultratrace elements of Encalilla seeds showed, in general, higher correlations with both seed protein and seed yield than did element concentrations of Patacamaya seeds. Results of scanning electron microscopy combined with energy dispersive X‐ray spectroscopy showed clearly differences in the contents of major mineral elements (calcium, magnesium, potassium, phosphorus, and sulfur) in the pericarp and embryonic axis (cotyledon + radicle). Obtained data could indicate that genotype × environment interactions are responsible for mineral variations occurring in quinoa cultivars. Results can also be useful for developing mineral biofortification strategies for the world's poorest regions.

The occurrence of functional chloroplasts in internal stem tissues and their distribution profiles in 20 woody species have been investigated. Chloroplasts were identified from the red chlorophyll auto-fluorescence using epi-fluorescence microscopy. Chloroplasts were detected in the cortex of all species examined, in the xylem rays of 19 and in the perimedullar and the pith cells of 16 out of the 20 investigated species. Chloroplast containing cell clusters in the pith were identified in some species. In addition, we report on the semi-quantitative distribution of chlorophylls in various internal stem tissues. Chlorophyll level was estimated by reflectance measurements at specific wave bands. Although decreasing chlorophyll gradients from cortex to pith were observed in half of the species, chlorophyll distribution in the remaining species was irregular with occasionally high levels in the pith. According to our data, chlorophyll occurrence in stem internal tissues is quite widespread, even in the light remote, deeply shaded central compartments like pith, provided that corresponding cells are viable. The species-specific tissue distribution of chlorophyll levels may be used to select suitable plants to investigate further this neglected area of photosynthesis research.

Summary• Reflectance indices are frequently used for the nondestructive assessment of leaf chemistry, especially pigment content, in environmental or developmental studies. Since reflectance spectra are influenced by trichome density, and trichome density displays a considerable phenotypic plasticity, we asked whether this structural parameter could be a source of variation in the values of the most commonly used indices.• Trichome density was manipulated in detached leaves of three species having either peltate ( Olea europaea and Elaeagnus angustifolius ) or tubular ( Populus alba ) trichomes by successive removal of hairs. After each dehairing step, trichome density was determined by light or scanning electron microscopy and reflectance spectra were obtained with a diode-array spectrometer.• Although species-specific differences were evident, most of the indices were considerably affected even at low trichome densities. In general, the less-affected indices were those using wavebands within the visible spectral region. The index that could be safely used even at very high hair densities in all species was the red edge index ( λ RE ) for chlorophyll.• The results indicate that changes in reflectance indices should be interpreted cautiously when concurrent changes in trichome density are suspected. In this case, the red edge for chlorophyll content may be the index of choice.