prepared by using razor blade from fruit apex, equator and stemend zones, respectively. The pieces were then pre-fixed with 3%glutaraldehyde in 50 mM phosphate buffer (pH 7.0) for 24 h, post-fixed with 1% osmic acid for 1 h, and dehydrated in vacuo. Samplesdipped in isoamyl acetate for 2 h were dried in a critical pointdryer, mounted on a sample supporter and coated with gold for8 min in a vacuum evaporator. The samples were observed underscanning electron microscopy (SEM) (Hitachi S-4000, Japan) andphotographed. To assess stoma development, long axis of the stomawas measured using at least 20 stomata at each sampling date. Thepercentage of collapsed stoma (Fig. 1D) was also calculated usingat least 40 stomata.