Brodiaea santarosae
The Santa Rosa Basalt Brodiaea

Tom Chester, Wayne Armstrong and Kay Madore

Distinguishing Characteristics of Brodiaea santarosae: Scaling of Floral Parameter Lengths With Perianth Length

Most species have flowers in which all the floral parts (styles, ovaries, anthers, etc.) grow larger as the perianth grows larger. The following figures plot the measured lengths for the seven basic flora parameters versus the total perianth length for each flower of B. santarosae. A linear least-squares fit is shown for each parameter.

As expected, most of the floral parts have a positive slope; i.e., they do indeed get larger as the perianth gets larger. The strongest effect (the steepest line going up to the right) is for the perianth lobes. This of course isn't surprising since the perianth length is the sum of the length of the perianth tube and the perianth lobes.

But surprisingly, the perianth tube did not scale with the perianth length at all. As the lobes got longer, the perianth tube did not systematically change in length. This is different from the other three species of B. filifolia, B. orcuttii and B. terrestris ssp. kernensis, for which both the perianth tubes and lobes scaled positively with perianth length.

Also, the ovary length did not scale with the perianth length, again unlike the ovaries of the other three species.

It is tempting to say that these values have simply reached their maximum values for the large flowers of B. santarosae, but as mentioned above, both characteristics grew with perianth length B. terrestris ssp. kernensis, which had equally large flowers.

Although the fitted slope of the staminode length for B. santarosae was actually negative with perianth length, indicating a tendency for the maximum staminode length to decrease with increasing perianth length, the statistical significance of the slope is low, and we cannot confidently make any conclusion here. As seen in the plot, the staminode length is so variable that it is impossible to deduce any trend to the data. (Be sure to note all the large staminode lengths of 6-7 mm at small perianth lengths.)

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Copyright © 2007 by Tom Chester, Wayne Armstrong and Kay Madore.
Comments and feedback: Tom Chester
Last update: 16 October 2007