Markus Riederer1, Katja Arand2, Markus Burghardt2, Hua Huang2,3, Michael Riedel2, Ann-Christin Schuster2, Anna Smirnova2,4, Yueming Jiang3. 1. Julius von Sachs Institute of Biological Sciences, University of Würzburg, Julius-von-Sachs-Pl. 3, 97082, Würzburg, Germany. riederer@uni-wuerzburg.de. 2. Julius von Sachs Institute of Biological Sciences, University of Würzburg, Julius-von-Sachs-Pl. 3, 97082, Würzburg, Germany. 3. South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Tianhe District, Guangzhou, 510650, People's Republic of China. 4. Génétique Moléculaire, Génomique, Microbiologie, Institut de Physiologie et de la Chimie Biologique, Université de Strasbourg, 21 rue René Descartes, 67084, Strasbourg Cedex, France.
Abstract
MAIN CONCLUSION: In litchi and longan fruits, a specialised pericarp controls water loss by a protective system consisting of two resistances in series and two water reservoirs separated by a barrier. In the fruits of litchi (Litchi chinensis) and longan (Dimocarpus longan), the pericarp is solely a protective structure lacking functional stomata and completely enclosing the aril that is the edible part. Maintaining a high water content of the fruits is crucial for ensuring the economic value of these important fruit crops. The water loss rates from mature fruits were determined and analysed in terms of the properties of the pericarps. Water loss kinetics and sorption isotherms were measured gravimetrically. The pericarps were studied with microscopy, and cuticular waxes and cutin were analysed with gas chromatography and mass spectrometry. The kinetics of fruit water loss are biphasic with a high initial rate and a lower equilibrium rate lasting for many hours. The outer and inner surfaces of the pericarps are covered with cuticles. Litchi and longan fruits have a unique type of transpiration barrier consisting of two resistances in series (endo- and exocarp cuticles) and two reservoirs of water (aril and mesocarp). The exocarp permeability controls the water loss from fresh fruits while in fruits kept for an extended time at low relative humidity it is determined by the endo- and exocarp permeabilities. Permeances measured are within the range for typical fruit cuticles. The findings may be used to design optimal postharvest storage strategies for litchi and longan fruits.
MAIN CONCLUSION: In litchi and longan fruits, a specialised pericarp controls water loss by a protective system consisting of two resistances in series and two water reservoirs separated by a barrier. In the fruits of litchi (Litchi chinensis) and longan (Dimocarpus longan), the pericarp is solely a protective structure lacking functional stomata and completely enclosing the aril that is the edible part. Maintaining a high water content of the fruits is crucial for ensuring the economic value of these important fruit crops. The water loss rates from mature fruits were determined and analysed in terms of the properties of the pericarps. Water loss kinetics and sorption isotherms were measured gravimetrically. The pericarps were studied with microscopy, and cuticular waxes and cutin were analysed with gas chromatography and mass spectrometry. The kinetics of fruit water loss are biphasic with a high initial rate and a lower equilibrium rate lasting for many hours. The outer and inner surfaces of the pericarps are covered with cuticles. Litchi and longan fruits have a unique type of transpiration barrier consisting of two resistances in series (endo- and exocarp cuticles) and two reservoirs of water (aril and mesocarp). The exocarp permeability controls the water loss from fresh fruits while in fruits kept for an extended time at low relative humidity it is determined by the endo- and exocarp permeabilities. Permeances measured are within the range for typical fruit cuticles. The findings may be used to design optimal postharvest storage strategies for litchi and longan fruits.
Entities:
Keywords:
Cuticular waxes; Pericarp; Plant cuticle; Water loss kinetics; Water permeability; Water sorption