tailieunhanh - Polar nuclei behaviour in the mature megagametophyte of the natural tetraploid Trifolium pratense (Fabaceae)

The mature female gametophyte in Trifolium pratense L., a natural tetraploid plant, consists of 7 cells: the egg cell, 2 synergids, the central cell, and 3 antipodal cells. This type of mature female gametophyte is known as polygonum. The central cell occupies the largest portion of the mature female gametophyte and the polar nuclei are situated close to the egg apparatus. | Turkish Journal of Botany Research Article Turk J Bot (2013) 37: 537-541 © TÜBİTAK doi: Polar nuclei behaviour in the mature megagametophyte of the natural tetraploid Trifolium pratense (Fabaceae) Hatice Nurhan BÜYÜKKARTAL Department of Biology, Faculty of Science, Ankara University, Tandoğan, Ankara, Turkey Received: Accepted: Published Online: Printed: Abstract: The mature female gametophyte in Trifolium pratense L., a natural tetraploid plant, consists of 7 cells: the egg cell, 2 synergids, the central cell, and 3 antipodal cells. This type of mature female gametophyte is known as polygonum. The central cell occupies the largest portion of the mature female gametophyte and the polar nuclei are situated close to the egg apparatus. The cytoplasm of the central cell is rich in organelles. A large number of rough and smooth endoplasmic reticulum, mitochondria, plastids, dictyosomes, ribosomes, starch, and lipid bodies were observed. Differences were identified in this plant between the sizes of polar nuclei and secondary nuclei generated by the fusion of the former. It was observed that the polar nuclei had fused long before the pollen tube entered the female gametophyte, and that the secondary nuclei in some female gametophytes were degenerated before fertilisation. Key words: Central cell, female gametophyte, polar nucleus, Trifolium 1. Introduction Tetraploid Trifolium pratense L. is an economically important forage legume naturally grown in Turkey for its tetraploid characteristics and high protein capacity. This naturally occurring tetraploid (2n = 4x = 28) is generally superior to the diploid forms in yield, disease resistance, and persistence (Taylor & Smith, 1979). A large number of seeds are required for natural tetraploid T. pratense to be grown in large areas, but there are problems with seed setting in this plant. Female gametophyte development .