Pollen Morphology, Viability, and Germination of Tanacetum vulgare L.

The pollen morphology of aromatic Tanacetum vulgare L. (Asteraceae), which has wide horticultural and medicinal uses, was examined using light microscopy and scanning electron microscopy. The investigation revealed that pollen grains are radially symmetrical, isopolar, spheroidal, tricolporate, and echinate–perforate. Average pollen length was 21.32 ± 1.12 μm, whereas average pollen width was 20.04 ± 0.98 μm (length:width ratio 0.94). Spine length was 2.72 ± 0.29 μm. Average distance from the spines was 7.15 ± 0.31 μm. Pollen exine consisted of 1–3 pores. Pori are elongated and also with a distinct margin. The porus latitude is smaller than the colpus latitude. One to three perforations were noticed on 1 μm2 of exine. Fluorescein diacetate was used to assess the viability of T. vulgare pollen. The effect of sucrose (1%, 5%, 10%, 20%, and 30%, w/v) on pollen germination and tube growth was evaluated. Overall, the inclusion of sucrose in the medium improved both pollen germination and tube growth. Also, pollen nucleus status was determined. Binucleate and trinucleate mature pollens were observed. Overall, the palynological features of this species may be helpful for further taxonomical and pharmaceutical investigations.

The chromosomal location of a gene (msg) affecting megasporogenesis in durum wheat

An aneuploid durum wheat line (Triticum turgidum L. var. durum) having 13 chromosome pairs and 2 unpaired chromosomes at metaphase I of meiosis in pollen mother cells (i.e., monosomic for chromosomes 7A and 7D) was observed to produce some progeny plants with 2n = 40 chromosomes. These aneuploid (triploid) plants were usually weak and sterile. Triploid plants also occurred in the progeny of durum plants monosomic for chromosome 7A, or in progeny of plants that were mono-telodisomic or ditelomonotelosomic for chromosome 7Aq (13 II + 1 t II or 13 II + t II + t I) but not in the progeny of plants ditelomonotelosomic for chromosome 7Ap (13 II + t II + t 1). Therefore, there is a gene(s) on chromosome arm 7Ap that prevents the production of diploid (2n) egg cells in wheat. In the absence of 7Ap, a portion of the egg cells have 26 chromosomes, which when fertilized with a pollen nucleus with 14 chromosomes, produces progeny plants with 2n = 40 chromosomes. The data also indicated that chromosome arm 7Dp probably contains a second gene that is capable of preventing the production of triploid plants. Key words: Triticum turgidum L. var. durum, polyploidy, aneuploid, triploid, monosomic.

Evolution du contenu en DNA nucléaire dans les gamétophytes mâles du Datura innoxia au cours de la période favorable à l'androgenèse

The nuclear DNA content was estimated by densitometry for six stages during the maturation of male gamétophytes of Datura innoxia Mill. Changes in nucleus size and structure (distribution of chromatin) were analysed simultaneously. The following were found. (a) After the tetrad stage, DNA synthesis preceding the first haploid mitosis took place progressively and slowly. Once this division was terminated, the pollen nuclei had the same DNA content (1C). When the period favoring embryogenesis was completed, the DNA content of the reproductive nuclei approached 2C while there was a tendency for the vegetative nuclei to undergo endomitosis. (b) A direct correlation between DNA content and size of pollen nuclei was only noted for the stages having identical nuclear structures. (c) The stage during which the pollen grain had the greatest embryological potential was a period of complete change in the DNA content (change from postsynthetic to presynthetic). (d) The fusion of the 2C reproductive nucleus with the 4C vegetative nucleus could lead to the formation, after a normal mitosis, of a 3C pollen nucleus; that would explain the formation of androgenic triploid seedlings found in Datura innoxia. [Translated by the Journal]