The genus Plantago (Plantaginaceae) in New Zealand comprises species that can be difficult to delimit and contains a wide range of ploidy levels from diploid to 16-ploid. To investigate whether there have been changes in genome size associated with polyploid events and whether pollen and guard cell size can be used as an initial guide to identify polyploids, we have used flow cytometry with propidium iodide as the stain to measure the genome size (DNA C-value) in a range of Plantago species with different ploidy levels. Light microscopy was used to measure pollen diameter and guard cell length in these plants to see whether these could be used for ploidy level identification. Large differences in C-value were observed between species but the extent of changes associated with different polyploid events was highly variable. Pollen diameter was correlated with C-value but not necessarily with ploidy level. Guard cell lengths were different between diploids and polyploids but not between the different polyploid species. The significance of the changes in genome size and its relationship to pollen and stomatal guard cell size is discussed.

The cosmopolitan plant genus Plantago contains species with a wide range of chromosome numbers in its New Zealand endemic representatives. These species are diploid, tetraploid, octoploid, decaploid, dodecaploid and 16-ploid. Using genomic in situ hybridization, we have shown that some of these polyploids contain at least three different genomes, confirming their allopolyploid status. Fluorescence in situ hybridization with 5S and 45S rDNA probes showed a wide variety of species-specific patterns of distribution in the polyploid species, suggesting that polyploidy has been accompanied by genomic reorganization.

Rice nodal segments from three flowering haploids were excised and treated for different lengths of time with 0.3% or 0.4% colchicine (dissolved in 2% DMSO) in an attempt to induce fertile seeds. A combination of higher colchicine concentration and longer hours of treatment reduced the survival rate of treated segments, but more fertile plants were transformed. Pooled data showed that of the 842 segments used, 42.2% survived the treatment and sprouted, but only 31.9% were successfully established and grown to maturity. Among the 269 mature plants, 29,4% produced fertile seeds (panicles) with an average of 146.2 seeds per diploidized plant.

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