Reproductive biology of the olive (Olea europaea L.) cultivar 'nabali baladi'

摘要

'Nabali Baladi' is the most common olive cultivar in Jordan. The final fruit set is very low, Specially in orchards planted only with this cultivar. This problem is very common in olive cultivars. Thus, the investigations focused on the development and the morphology of the reproductive organs: pollen grain quality and quantity,pollen germination and pollen tube growth, fertilisation and fruit set. Another two olive cultivars "Grossa de Spagna' and "Rasie' were used for cross-pollination. One month before anthesis, the two tetrasporangiate anthers were developed. About three weeks before anthesis, the microspore mother cells were observed clearly. Through a week, they developed to the microspore tetrade stage. Finally, the fully developed pollen grains could be observed about five days before anthesis. The pollen grain number of the pollinizers was higher than in 'Nabali Baladi'. The normal pollen grains were more than 82% for the three cultivars in both year. The pollen viability was tested on an agar medium 0, 8%, containing 10% sucrose and 50 ppm citric acid. Immersion of the pollen grains in olive oil before spreading them on the medium improved this test significantly. The pistil consists of a superior ovary, short style, and wet papillate stigma. It was developed about six days before anthesis. A protuberance structure arised from the placenta of the ovary about four weeks before anthesis which developed to the anatropous ovule. Each carpel contained two ovules and only one ovule developed to the seed. The first embryo sac mother cell could be recognised in the middle of the ovule about two weeks before anthesis. The embryo sac with eight nuclei was completed about two days before anthesis. The pollen tubes grew intercellularly through the stigma and the transmitting tissue in the style. One pollen tube entered the ovary to fertilise one ovule through the micropyle. The stigmas with a high pollen grain number had also a high number of germinated pollen grains. The flowers which had less than ten germinated pollen grains on the stigma had lower percentage of fertilised ovaries. In most of self-pollinated flowers, all germinated pollen grains could not penetrate the transmitting tissue in the style, while in open and cross-pollination, most of the flowers had germinated pollen grains, and the tubes grew through the transmitting tissue in the style. In open- and cross-pollinatin, the pollen tubes started to enter the ovules two to three days before in self-pollination. In addition to that, the percentage of the fertilised ovules in open-and cross-pollination was about three times higher than in self-pollination. One week after anthesis, there was no difference in length between the fertilised and the non-fertilised ovules. Two weeks after anthesis, the ovule length doubled and the non-fertilised ovules degenerated. From the third week till the seventh week after anthesis, the ovule grew almost logarithmically. Eight weeks after anthesis till the mature stage, there was no further increase in the ovule size. The nuclear endosperm started to develop five days after anthesis. It became cellular 15 days after anthesis. The absorption of the nucellus tissue and the endosperm was very clear during the embryo development. The zygote was observed nine days after anthesis. Four and five weeks after anthesis, it developed to a long narrow suspensor. Six weeks after anthesis, the embryo reached the globular stage. One week later, it started to develop two cotyledons (heart-shaped) which developed quickly to the full length 12 weeks after anthesis. Finally, the embryo and the partly absorbed endosperm reached the final stage about 22 weeks after anthesis. The perfect flowers abscised in two ways: the non-fertilised perfect flowers abscised through the second week after anthesis, and part of the fertilised flowers abscised from two to six weeks after anthesis. After that, there was no significant fruit drop. The fruit set in open-and cr