Friday, May 30, 2008

Plants are parasites too!

The other day while hiking the Ahwingna Trail in the Hacienda Hills, I noted a patch of California buckwheat covered with a substantial amount of dodder (also referred to as "witch's hair"). Dodder is a plant with viney, hair-like, yellow to bright orange stems that sprawl all over the shrubs that it covers. Many times before I have been in the field with people who have asked me about this plant, whether it is native, and why it grows on other plants. In fact, the plant is a native, but it is one of the few parasitic plants that have the potential to occur in the Puente Hills. The lack of green (i.e., chlorophyll) in the plant is an indication that it does not produce its own food via photosynthesis. Instead, this plant must take its nourishment from other plants, and in the process harms the host plant to some degree. When dodder covers extensively, it blocks the underlying plants and prevents them from getting enough sunlight for photosynthesis. Once dodder germinates from a seed, it needs to grow quickly and attach itself to its host plant. In order to get food from the host plant (such as buckwheat), dodder inserts root-like structures into the host's stems in order to draw nourishment from the host. Our local species of dodder is mostly partial to buckwheat, sages, and deerweed.

Another parasitic plant that is common in southern California (though not in the Puente Hills) is mistletoe. Almost all species of mistletoe are hemi-parasitic (or partially parasitic). The plant is green, and so produces it own food via photosynthesis. However mistletoe grows high up on the branches of its host trees (such as sycamore) and so it is not rooted in the soil to get water. As such, the mistletoe must take water directly from the stems of the host tree that it grows on.

1 comment:

wdbtcr said...

Now I know what that orange stuff (dodder/witches hair) is! I see it all the time when I hike and figured it was parasitc in some way, but didn't know what it was called. Witches hair...very appropriate. Thanks for the info.