Pollen viability and pollen vigor.

Investigations were carried out to correlate pollen viability, assessed on the basis of a fluorochromatic reaction (FCR) test, with pollen vigor, assessed on the basis of the time taken for in vitro germination in pollen grains subjected to high humidity (>95% RH) and temperature (38 °C) or storage stress of Nicotiana tabacum, Agave sp., Tradescantia virginiana, and Iris sp. Both high RH and temperature, as well as storage stresses, affected pollen vigor before affecting pollen viability. The results are discussed in the light of available data on the viability and vigor of stressed pollen and of aged seeds. The need for consideration of pollen vigor, particularly in stored pollen, the inadequacy of the methods presently used, and some of the methods suitable to assess pollen vigor are elaborated.

Temperature effects on self incompatibility in Lilium longiflorum.

Detached pistils of the clonal variety, Lilium longiflorum 'Aral No. 5', were submerged before pollination in 50°C water for 0, 1, 2, 3, 4, 5, 6 or 7 min and then immediately compatibly and incompatibly pollinated. Incompatibility, as indicated by pollen tube length after 48 h at 23.5°C, was eliminated by a 1-2 min submersion while compatibility was removed by a 4-5 min one. The 'window' of incubation temperatures at which incompatible and compatible pollen tubes are clearly differentiated occurred between 15 and 30°C.

Wall-bound proteins of pollen tubes after self- and cross-pollination in Lilium longiflorum.

Wall-bound proteins of Lilium longiflorum pollen tubes grown in vivo constitute 20-27% of the dry matter. Twenty-two-twenty-six percent of these proteins are NaCl soluble. Wall-bound proteins of in vivo pollen tubes are present in amounts 5-7 times that found in tubes grown in vitro. The protein pattern of wall-bound proteins is different between in vitro and in vivo grown pollen tubes. There are two kinds of pollen tube wall proteins: loosely bound and tightly bound. The latter are NaCl insoluble, contain hydroxyproline and are assumed to be covalently bound. No significant differences have been found in the amount of wall-bound proteins present between pollen tubes resulting after self-pollination and those resulting from cross-pollination. However, some band differences between self- and cross pollen tubes have been observed after gel electrophoresis. It can be supposed that some wall-bound proteins of pollen tubes are associated with the incompatibility reaction.

Cell-wall proteins in pollen and roots of Lilium longiflorum: extraction and partial characterization.

Cell-wall proteins of pollen grains, in-vitro-germinated pollen and young roots of Lilium longiflorum were studied by gel electrophoresis and amino-acid analysis. The proteins were removed from extensively purified walls by successive saline and alkali extractions. The major part including the hydroxyproline-containing proteins is covalently bound to the wall. Clear differences were observed between the proteins, especially the glycoproteins, of the pollen grain and the pollen tube. During elongation of the tubes some proteins decrease in quantity and many new proteins appear. The amount of protein in the cell walls is much lower in roots than in pollen and the root cell walls also contain fewer glycoproteins.

Studies on the self-incompatibility of Petunia hybrida in excised-style culture. Differences in self-incompatibility reaction among four clones.

In Petunia clones with different S-alleles, self- or cross-pollinated excised-styles of 5, 10, 15, 20 or 25 mm were incubated on a standard agar medium for 24, 48 or 72 h. The length and number of protruding incompatible pollen tubes were compared with those of compatible ones. Throughout the experimental period, the length and number of incompatible pollen tubes of pollen from the S1S1-clone were always less than those of compatible ones. In pollen from S2S2-, S3S3- and S2S3-clones the incompatible pollen tube growth was barely arrested in 5 and 10 mm excised-styles during the first 24 h of incubation. However, inhibition of incompatible pollen tube growth was strengthened with the increase of both excised-style length and incubation period: this was clearly evident in 15 mm or longer excised-styles incubated for 48 h. Ratios of incompatible to compatible pollen tube length in excised-styles incubated for 72 h, were for S3S3 pollen tubes = 0.28, S1S1=0.48, S2S3 = 0.50, and S2S2 = 0.60, and ratios on tube numbers were S3S3 = 0.01, S1S1 = 0.1, S2S2 = 0.21, and S2S3 = 0.21. These results were in agreement with those of in vivo self-pollination. The incompatibility reaction seemed strongest in S3S3-, weaker in S1S1 - and weakest in S2S2- and S2S{3}-clones, and therefore the intensity of S-allele expression would be S3> S1> S2.

Localization of phytic acid in the floral structure of Petunia hybrida and relation to the incompatibility genes.

In three clones of Petunia hybrida with different incompatibility genes, phytic acid is detected exclusively in pollen, stigma and style. These are all parts of the floral structure involved in the incompatibility reaction. Phytase activity was detected in these tissues as well as in the ovary. The level of phytic acid and phytase activity varied between clones with different S alleles. This difference was most evident in stigma and style. The pattern of phytic acid breakdown following pollination depends on whether pollen and style form a compatible or incompatible combination. Incompatible pollination results in a higher rate of degradation. Consideration is given to the relationship between breakdown of phytic acid to myo-inositol and cell wall thickening and plug formation, which occurs to a greater extent in the incompatible combination.

Protein synthesis in germinating pollen of Petunia: role of proline.

Pollen of Petunia hybrida was germinated in artificial medium. At the beginning of the incubation, a large amount of proline, which comprises about half of the total free amino acid pool, was released into the medium. Part of this proline is reutilized by the pollen. Uptake of radioactive amino acids and their incorporation into proteins were studied. The highest rate of protein synthesis was found directly after the onset of germination. The endogenous free proline pool was found to be compartmentalized; one of the compartments is the protein precursor pool; its size is probably much less than 50% of the total free proline in the pollen.