Fruit Development of Pistacia vera (Anacardiaceae) in Relation to Embryo Abortion and Abnormalities at Maturity

Abstract

This study investigated fruit development of the Pistacia vera L. cultivars Kerman and Sirora using bright field microscopy. Normal fruit development was compared with that of seedless (blank) and small seeded (semi-blank) fruits to identify the stages at which degeneration occurred. In normal fruits, pericarp growth took place up to week 4 after pollination and preceded embryo, endosperm and funicle proliferation between weeks 4 and 16. Endocarp (shell) and exocarp (hull) development occurred between weeks 8 and 16. Blank and semi-blank fruits were identified by slower growth and lack of exocarp colouration. Blank fruits resulted from one of five patterns of ovule degeneration caused by funicle degeneration, embryo sac absence, embryo sac degeneration, lack of pollen tube penetration of the embryo sac, or failure of endosperm cellularisation. Funicle degeneration was the most common cause of blanking and was observed either at the site of pollen tube penetration or at the chalazal end of both pollinated and unpollinated ovules. Degeneration of funicular tissue extended towards the vascular bundles. Small seeded or semi-blank fruit resulted from degeneration of the cotyledons during the latter stage of embryo development.