AUTHOR=Chen Xia , Gao Jianguo , Zhao Ping , McCarthy Heather R. , Zhu Liwei , Ni Guangyan , Ouyang Lei 

TITLE=Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00030

DOI=10.3389/fpls.2018.00030

ISSN=1664-462X

ABSTRACT=<p>An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (<italic>Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora</italic>, and <italic>Eucalyptus grandis</italic> × <italic>urophylla</italic>) and without (<italic>Castanopsis fissa, Schima superba</italic>, and <italic>Acacia auriculiformis</italic>) photosynthetic stems, and the sap flux (<italic>J</italic><sub>s</sub>) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the <italic>F</italic><sub>v</sub>/<italic>F</italic><sub>m</sub> (Maximum photochemical quantum yield of PSII) and Φ<sub>PSII</sub> (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that <italic>J</italic><sub>s,d</sub> (daytime sap flux) and <italic>J</italic><sub>s,n</sub> (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (Slope<sub>SMA</sub> = 2.680) than in non-photosynthetic stems species (Slope<sub>SMA</sub> = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.</p>