- The structure of the pistil of tetraploid Pelargonium Xhortorum (2N = 36), with respect to the vascular system and the path and nature of the transmitting tissue, was determined.
For a given plant, pollen germination and percent pollen tubes descending the pistil to the ovary were constant for both self- and cross-pollinations; however, seed-set was higher for cross-pollinations. No significant difference was observed for percent pollen germination or percent pollen tube growth for self- or reciprocal cross-pollinations with diploids and their autotetraploids. The number of pollen tubes descending the pistil were influenced by the stigma. Seed-set was higher during the cooler winter months. The lower seed-set for self-pollinations and during the warmer months was a result of embryo abortion.
Polysiphony and branched pollen tubes were observed in fertile and sterile plants. As the pollen tubes approached the ovules, especially in self-pollinated pistils, they often became filled with callose, appeared spirally-ropy, and some were observed to veer away from the ovules toward which they were growing.
There was a preponderance of univalents and bivalents at diplotene. Upon inbreeding the number of univalents increase, the number of multivalents and chiasmata decrease, and the number of bivalents remains constant. The linear configurations of both trivalents and tetravalents appeared most stable. Although there are large numbers of univalents at diplotene, disjunction at anaphase I is relatively regular. It is suggested that, due to the multispecific nature of P. Xhortorum, many of the univalents may have been formed from pre-diplotene terminalization of pachytene pairing. Their kinetochores would therefore be properly polarized, and the univalents would move normally through anaphase I. Interchromosomal fibers were observed in both fertile and sterile plants. It is possible that these fibers aid in the non-random movement of the univalents to their proper poles in the cell. An unexplained high correlation exists between numbers of univalents and trivalents with seed-set.
- Dissertation Note:
- Ph.D. The Pennsylvania State University 1986.
- Source: Dissertation Abstracts International, Volume: 47-11, Section: B, page: 4405.
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