There are approximately 450 species of oaks (Quercus L., Fagaceae) and they are the dominant tree species in many ecosystems and landscapes throughout the Northern Hemisphere (Plomion et al., 2016).Classifying oak trees is challenging because of the existence of a large number of interspecific morphological characteristics and intraspecific morphological variations, partly due to hybridization and introgression, subsequently influencing the phylogenetic reconstruction of oak spe-

Key message It reports relevant traits of diploid and autotetraploid apple plants ('Hanfu' and 'Gala') in response to drought. The differences indicate that apple plants ('Hanfu' and 'Gala') may differ in their response to drought stress depending on ploidy level. Abstract The induction of polyploidy ameliorates the adverse effects of drought in many plants. In this study, the tolerance responses of diploid and autotetraploid apple with two cultivars were compared under drought stress treatment induced by polyethylene glycol (PEG)-6000 in the laboratory. Autotetraploid apple plants were previously induced in vitro from the diploid apple (Malus 9 domestica, 2n = 2x = 34) cultivar 'Hanfu' and 'Gala' by colchicine treatment. In this study, we elucidated the effects of drought stress on apple by investigating the following parameters in leaves: relative water content (RWC), proline content, malondialdehyde (MDA) content and expression of key aquaporin genes. Under drought stress, autotetraploid apple had higher RWC and chlorophyll fluorescence parameters and lower levels of MDA and proline compared with diploid apple. Key aquaporins genes were induced in leaves in response to PEG6000 treatment, including MdPIP1;1 and MdTIP1;1. The expression of these genes induced under drought stress treatment, and the genes were expressed at lower levels in the autotetraploid than in the diploid. Our combined physiological and molecular data reveal that polyploidization can enhance drought tolerance in 'Hanfu' and 'Gala' apple.

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Rice and drinking water are recognized as the dominant sources of arsenic (As) for human intake, while little is known about As accumulation and speciation in Chinese Herbal Medicines (CHMs), which have been available for many hundreds of years for the treatment of diseases in both eastern and western cultures. Inorganic arsenic was the predominant species in all of CHMs samples. The levels of inorganic arsenic in CHMs from fields and markets or pharmacies ranged from 63 to 550 ng/g with a mean of 208 ng/g and 94 to 8683 ng/g with a mean of 1092 ng/g, respectively. The highest concentration was found in the Chrysanthemum from pharmacies. It indicates that the risk of inorganic As in CHMs to human health is higher in medicines from markets or pharmacies than that collected directly from fields. Some CHMs may make a considerable contribution to the human intake of inorganic arsenic.