This is the final post in my series on photosynthesis in Mohave desert plants. While green leaves are commonly considered as the primary sources of photosynthesis, higher plants can potentially use almost all vegetative and reproductive structures to perform carbon fixation. Chlorophyll-containing bark and wood tissue, most fruit, root and fertile flower organs typically perform an effective internal CO2 recycling using the respiratory released CO2. Photosynthetic stems have positive effects on the carbon economy of plants through two main mechanisms. Photosynthetic stems can either assimilate atmospheric CO2 and contribute to the net carbon gain of the plant through the process of stem net photosynthesis, or decrease respiratory losses by recycling CO2 previously respired by roots and stems through the process of stem recycling photosynthesis.Plants with green stems are categorized by one of three types of stem photosynthesis syndromes. Retamoids include leafless or almost leafless woody plants that have stomata in the stem epidermis allowing for gas exchange with the atmosphere (Schaedle 1975). Another type of photosynthetic stems are the succulent pachycauls or the sarcocaulescent group, which has large-sized stems with translucent exfoliating bark, a large amount of parenchymatous tissue that serves as a water reservoir, and non-succulent, drought-deciduous leaves (Franco-Vizcaino et al.1990). An example of this would be the Boojum Tree (Fouquieria columnaris) and the related Ocotillo (Fouquieria splendens) as both lack stomata and recycle respiratory released CO2 to survive during drought. Another type of photosynthetic stem is found in cactus, which take up carbon dioxide at night with stoma using CAM photosynthesis. The inadequacy of the current state of knowledge for describing or understanding the diversity of structure, function, and ecological significance of photosynthetic stems suggest areas for further research. The diversity of taxonomic types, and classes of photosynthetic stems, results in a large diversity of structural characteristics. In this post, I have simply chosen interesting examples without resolving these difficulties. I have also decided to throw caution to the wind and use lots of technical jargon.
Death Valley is famous for its spectacular, spring wildflower displays, but those are the exception, not the rule. Only under perfect conditions does the desert fill with a sea of gold, purple, pink or white flowers. Although there are years where blossoms are few, they are never totally absent. Most of the showy desert wildflowers are annuals, also referred to as ephemerals because they are short-lived. Oddly enough, this limited lifespan ensures survival here. Rather than struggle to stay alive during the desert’s most extreme conditions, annual wildflowers lie dormant as seeds. When enough rain finally does fall, the seeds quickly sprout, grow, bloom and go back to seed again before the dryness and heat returns. The majority of these blooms are produced by Desert Gold (Geraea canescens). The Badwater Road along the side of Death Valley is still the go-to destination for those huge expanses of endless flowers. Fortunately for me, Death Valley is only about two hours from Las Vegas.
In the spring, the desert around Las Vegas can erupt with a riot of colors and forms during the wildflower bloom. Every spring brings at least a few flowers, but in a good year, the desert can be carpeted with flowers. Good and bad years depend on rain, and the best flowers occur during years when there was several inches of rain during the preceding fall. It is always worth getting outdoors during March and April to take a look, but in years when there was good rain during October and November, don't miss it. When visiting the desert it is not often the quantity of blooms, but more often the quality. You might have to look a little closer, walk a little more and look among the rocks to find the treasures but I can promise you it will be worth the effort. This year I decided to focus on the Valley of Fire; these are a few of my finds. I hope you enjoy.