Taisha writes today’s entry:
Today’s photo of Cryptantha flava, or the yellow cryptanth, was requested from hauskurz@UBC Botanical Garden forums, who posted it in this plant identification thread: Cryptantha flava. Thanks hauskurz!
The origin of the names for Cryptantha flava are the Greek words kryptos, meaning “to hide” and anthos meaning “flower”, as well as flava meaning “yellow”. Yellow cryptanth is a semi-arid perennial found growing in sandy soils of Arizona, Colorado, New Mexico, Utah, and Wyoming. This aboveground herbaceous species grows from a taproot and woody underground stem, called a caudex, that bears densely packed rosettes of oblanceolate leaves. The hairy leaves appear in the spring and senesce after they bear a single inflorescence of 45-55 yellow 5-petaled flowers. The flowers produce one, sometimes two, nutlets (two more may be fertilized but are aborted). These remain enclosed in the calyx until later serving as the dispersal unit (see: Casper, B. B. 1996. Demographic consequences of drought in the herbaceous perennial Cryptantha flava: Effects of density, associations with shrubs, and plant size. Oecologia. 106:144-152.).
In today’s photograph, there are flowers of both white and yellow on the same plant. Corolla colour is one way in which flowers attract animal pollinators. Some species have corollas which undergo colour changes as they age in order to attract or deter pollinators. By changing corolla colour, the plant is able to direct pollinators to flowers that have not yet been pollinated, increasing outcrossing. In some species, this colour change is onset by pollination.
In a study by Casper and La Pine, colour change from white to yellow in another member of Cryptantha, Cryptantha humilis var. nana, was investigated. It was theorized that the changes in colour and other floral characteristics occur in order to deter pollinators from visiting non-reproductive flowers. It was found that Cryptantha humilis var. nana is self-incompatible, and therefore visits from pollinators to viable flowers are essential to maximize seed production and reproductive potential.
They found that this phenomenon was a time-dependent event, regardless of whether the flower is pollinated. Observations revealed that approximately three days after anthesis (when the flower is fully open and functional), the flower turns white and remains so for about a day before wilting. It was discovered that other changes occur simultaneously with colour change such as decrease in nectar and pollen production, and differences in odour and UV patterns. It was also observed that pollinators visited plants of Cryptantha humilis var. nana that had yellow corollas more often than those with white, presumably because it is the flowers with yellow corollas that produce nectar. One might question the advantage of keeping corollas on the plant after pollination, and it is suggested that it may contribute to the attractiveness of the plant to pollinators from long distances. However, it was found that the white flowers did not increase the number of insect visitors, and it is actually the number of yellow flowers that pollinators made their foraging decisions on, rather than the total number of flowers. Overall, it is mentioned that more experimental approaches are necessary to understand the colour change phenomenon (see: Casper, B. B., La Pine, T. R. 1984. Changes in corolla color and other floral characteristics in Cryptantha humilis (Boraginaceae): Cues to discourage pollinators?. Evolution. 38(1): 128-141.).