Pollination of kiwifruit (Actinidia chinensisPlanch.): Stigma-style structure and pollen tube growth

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Abstract
The structure of stigma — style tissues in kiwifruit (Actinidia chinensis Planch. cv. ‘Hayward’) flowers was examined before, and after, hand-pollination and the course of pollen tube development was followed. At the time of flower opening the style had a well defined canal which opened at its distal end to form a V-shaped stigmatic furrow. The surface of the furrow was covered with unicellular papillae. The exposed wall of each papilla was covered with a cuticle and a distinct pellicle. The papillae were supported by a layer of hypodermal cells and an extensive layer of thin-walled transmitting cells. The transmitting tissue extended from the tip of the style through the stylar canal to its junction with the ovary. A single vascular strand, which extended along the length of the style adjacent to the stylar canal, branched into the stylar parenchyma on each side of the V-shaped furrow. Pollen grains germinated on the stigmatic papillae and grew through the intercellular spaces of the transmitting tissue. Pollen tubes were restricted to the transmitting tissue in the lower half of the canal adjacent to the vascular strand. Starch grains in the stylar parenchyma and transmitting tissue progressively disappeared as the pollen tubes traversed the length of the style. The most rapidly growing pollen tubes reached the base of the style in 31 hr and fertilisation of some ovules had occurred 42 hr after pollination. Fertilisation continued until 74 hr after pollination.