*4.1. Preharvest Application of Chitosan Increased the Weight of 'Garmrok' Kiwifruit at Harvest*

In our previous study, we showed that the preharvest treatment of calcium chitosan (100 mg·L<sup>−</sup>1) increased the fruit weight with no effect on the size of kiwifruit at harvest [8]. A recent similar study demonstrated that the preharvest spray of chitosan increased the

single fruit weight with the equivalent yield of kiwifruit without affecting the size of the fruit [22]. Here, we show that the application of preharvest chitosan also increased the fruit weight and delayed maturation and ripening of the kiwifruit. The influence of preharvest treatment of chitosan manifested throughout the cold storage is reflected on the physicochemical and molecular attributes in kiwifruit.

It was considered that the increased fruit weight by the treatment of chitosan is associated with the formation of a semipermeable barrier on the fruit surface that may have reduced the water loss from transpiration and respiration [8]. When we examined the surface of the 'Garmrok' kiwifruit peel under a scanning electron microscope, this semipermeable barrier-forming characteristic of chitosan was observed as a coated film on the kiwifruit peel (Figure 7). The film coating of chitosan on the fruit surface can absorbs moisture due to the hydrophilic nature of chitosan solution [34] and this could be attributed to the increased weight of kiwifruit, which in turn reduced water loss from fresh fruit. Alternatively, the increased weight of chitosan-treated kiwifruit may be attributed to the activity as a biostimulant and growth elicitor, as demonstrated in *Capsicum annuum* 'Yolo Wonder' bell pepper [35], *Solanum lycopersicon* 'Faridah' tomato [36], and *A. deliciosa* 'Guichang' kiwifruit [22]. Future investigations on the detailed mechanistic insights as to the increased weight of fruits at harvest pretreated by chitosan further awaits.

**Figure 7.** Scanning electron micrographs (SEMs) of preharvest chitosan-treated and untreated 'Garmrok' kiwifruit peel surfaces. The arrows indicate the chitosan film on kiwifruit peel after coating. All micrographs are at 500X and the scale bars in each image represent the lengths of 100 μm.
