Abstract
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 Coffea arabica and Coffea canephora 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 (Tleaf), net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E), WUE, crop water stress index (CWSI), index of relative stomatal conductance (Ig), initial fluorescence (F0), 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 Coffea plants, KF decreased the Tleaf up to 6.7°C/5.6°C and reduced the CWSI. The plants that were not protected with KF showed lower A, gs, E, and Ig than those protected with KF. C. canephora plants protected with KF achieved higher WUE compared with those not protected by 11.23% in autumn and 95.58% in summer. In both Coffea sp., KF application reduced F0, 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 Coffea seedlings from the nursery shade to the full sunlight, to protect leaves against the excessive solar radiation and high temperatures, especially in C. canephora during the summer.
Highlights
The fine particle film of calcined and purified kaolin (KF) application is a technological product-oriented to sustainable use of water resources in various agricultural crops (Boari et al, 2014; Brito et al, 2018; Faghih et al, 2019)
The C. arabica is an understory tree and an endemic species originated at the Ethiopian rainforests at altitudes above 1,500 m characterized with an average annual temperature of 20◦C; C. canephora originated at West and Central Africa of altitudes from 0 to 1,200 m, characterized with average annual temperature between 24 and 26◦C, where it evolved as a mediumsized tree (Charrier and Berthaud, 1985)
kaolin film (KF) impacted a leaf temperature (Tleaf) decrease of 5.6◦C for C. arabica and 5.7◦C for C. canephora compared with GL in summer
Summary
The fine particle film of calcined and purified kaolin (KF) application is a technological product-oriented to sustainable use of water resources in various agricultural crops (Boari et al, 2014; Brito et al, 2018; Faghih et al, 2019). Fine kaolin films reduce negative UV impacts by increasing light reflection in apple, Malus domestica (Glenn et al, 2002); reduce leaf temperature by 1.1◦C in tomato, Solanum lycopersicum (Boari et al, 2014); reduce water stress in pepper, Capsicum annuum (Creamer et al, 2005); increase water use efficiency (WUE) by 26% in tomato (AbdAllah, 2019), and stomatal conductance (gs) in well-watered grapevines, Vitis vinifera (Glenn et al, 2010); increase leaf photosynthesis (A) in apple trees (Glenn et al, 2001); increase the sucrose biosynthesis in grapevines (Conde et al, 2018); increase height and diameter growth in young eucalyptus hybrid plants, Eucalyptus grandis × Eucalyptus urophylla (Santos et al, 2021). The C. arabica is an understory tree and an endemic species originated at the Ethiopian rainforests at altitudes above 1,500 m characterized with an average annual temperature of 20◦C; C. canephora originated at West and Central Africa of altitudes from 0 to 1,200 m, characterized with average annual temperature between 24 and 26◦C, where it evolved as a mediumsized tree (Charrier and Berthaud, 1985)
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