AUTHOR=de Abreu Deivisson Pelegrino , Roda Newton de Matos , de Abreu Gideao Pelegrino , Bernado Wallace de Paula , Rodrigues Weverton Pereira , Campostrini Eliemar , Rakocevic Miroslava 

TITLE=Kaolin Film Increases Gas Exchange Parameters of Coffee Seedlings During Transference From Nursery to Full Sunlight

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.784482

DOI=10.3389/fpls.2021.784482

ISSN=1664-462X

ABSTRACT=<p>Increases in water use efficiency (WUE) and the reduction of negative impacts of high temperatures associated with high solar radiation are being achieved with the application of fine particle film of calcined and purified kaolin (KF) on the leaves and fruits of various plant species. KF was applied on young <italic>Coffea arabica</italic> and <italic>Coffea canephora</italic> plants before their transition from nursery to full sunlight during autumn and summer. The effects of KF were evaluated through the responses of leaf temperature (T<sub>leaf</sub>), net CO<sub>2</sub> assimilation rate (<italic>A</italic>), stomatal conductance (<italic>g</italic><sub>s</sub>), transpiration (<italic>E</italic>), WUE, crop water stress index (CWSI), index of relative stomatal conductance (I<sub>g</sub>), initial fluorescence (F<sub>0</sub>), and photosynthetic index (PI) in the first 2–3 weeks after the plant transitions to the full sun. All measurements were performed at midday. In <italic>Coffea</italic> plants, KF decreased the T<sub>leaf</sub> up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower <italic>A</italic>, <italic>g</italic><sub>s</sub>, <italic>E</italic>, and I<sub>g</sub> than those protected with KF. <italic>C. canephora</italic> plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both <italic>Coffea</italic> sp., KF application reduced F<sub>0</sub>, indicating reduced physical dissociation of the PSII reaction centers from the light-harvesting system, which was supported with increased PI. The use of KF can be recommended as a management strategy in the transition of <italic>Coffea</italic> seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in <italic>C. canephora</italic> during the summer.</p>