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Pollen Of The Brodiaea elegans Hybrid

Until a satisfactory name is applied to these populations, I will refer to southern California populations
previously called "Brodiaea jolonensis" as "Coastal BTK" and mountain populations previously called
"Brodiaea terrestris ssp. kernensis" as "Montane BTK."
The flower color for Brodiaea species on this page is blue-purple to violet. In the following images
I have attempted to match their true color;  however, they may appear different on your monitor.

In the following images the pollen grains from a Brodiaea elegans hybrid were stained using acetocarmine. Viable pollen grains took up the stain and turned blue. Smaller, sterile (abortive) pollen grains remained hollow and transparent. According to Lyman Benson (Plant Taxonomy, 1962): "If, for example, more than half the pollen grains are abortive, probably something is amiss with the meiotic process preceeding pollen grain formation." One of the reasons that chromosomes in a hybrid mother cell do not separate normally is synaptic failure. Since the chromosomes come from two different species they are not truly homologous and fail to pair up properly at meiosis I. A classic example of meiosis gone amiss is the mule. The horse and donkey chromosomes line up properly for mitosis, but in meiosis they fail to pair up normally. In addition the mule has a chromosome number of 63 which cannot be divided equally into whole numbers (chromosomes). In plants, fertile polyploid hybrids occur when each chromosome set has a homologous set to pair up with. Diploid rabbages are typically sterile because the 9 cabbage chromosomes fail to pair up properly with the 9 radish chromosomes. Tetraploid rabbages are fertile because the 2 sets of cabbage chromosomes pair with each other, and the 2 sets of radish chromosomes pair with each other.

Hybrid brodiaeas have been observed in the wild where the ranges of two species overlap. In fact, Theodore Niehaus was able to hybridize every combination between all species and obtain seed (personal communication, 2004). The seeds grew into new plants and flowered in 2-3 years. Hybrid plants generally failed to set seed because of abnormal meiosis. This abnormality is reflected in a high percentage of abortive pollen grains. According to Niehaus (1971) A Biosystematic Study of the Genus Brodiaea (Amaryllidaceae), the majority of hybrids were completely sterile, but one plant showed 92 percent fertility. I assume the previous statement refers to the percentage of viable pollen. Hybrid plants studied by Niehaus had flowers that were morphologically intermediate between those of the two parents.

The following pollen images came from a possible hybrid between B. elegans ssp. elegans at Mission Trails Regional Park in San Diego County, and possibly nearby Coastal BTK (previously refered to as B. jolonensis). The percentage of viable pollen indicates that this "hybrid" is not sterile. It had 65% pollen viability which is not typical of a true interspecific brodiaea hybrid.

B. elegans "hybrid." The smaller, clear pollen grains are sterile (abortive).

B. elegans "hybrid." The smaller, clear pollen grains are sterile (abortive).

B. elegans "hybrid." The smaller, clear pollen grains are sterile (abortive).

Coastal BTK in San Marcos

Coastal BTK (Brodiaea terrestris ssp. kernensis): More than 97% of the pollen grains are fertile. Fewer than 3% are smaller, transparent blanks. Mature grains are approximately 50 micrometers (0.05 mm) long. An unfortunate flower thrip was dining on the anthers when the pollen sample was taken. This animal became part of the stained slide (lower left quadrant).

See Table Of Relative Cell Sizes

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