Plants: A Different Perspective
polymer… to store energy”12 for use at a later time when a plant needs energy when photosynthetic sources are lacking.
While chlorophyll (green) is perhaps the best-known photosynthetic pigment because of the dominant number of “green” plant species, other pigments also play a role in converting sunlight into useable energy. They include carotenoids such as carotene (orange), xanthophylls (yellow), and phycoerythrin (red). When engaging in photosynthesis, chlorophyll “absorbs its energy from the Violet-Blue and Reddish orange-Red wavelengths, and little from the intermediate (Green-Yellow-Orange) wavelengths,”13 while carotenoids and xanthophylls absorb some energy from the green wavelength, and phycoerythrin absorbs a significant amount of its energy from the blue wavelength. Many plants use multiple pigments for photosynthetic purposes, enabling them to maximize use of sunlight that falls on their leaves.
When comparing photosynthesis that occurs within red and green leaves, the latter which have greater concentrations of chloroplasts, scientific studies have shown that “green leaves are engineered to optimize productivity… enabling plants to [maximize] use of the visible light spectrum [and] to respond rapidly to changes in the spectral environment, as well as to exploit niche habitats.”14 Accordingly the rate of photosynthesis is higher in green-leafed plants when compared to red leafed plants.
In one experiment, green and red leaves were collected from the same deciduous tree and exposed to 5-10 minutes of light and another 5-10 minutes of darkness. Afterwards the change in Carbon Dioxide (CO2) levels was measured to determine the rate of photosynthesis. The “results showed that green leaves [had] a higher mean rate of photosynthesis (-.5855 parts per million (ppm) CO2/minute/gram) than red leaves (-0.200 ppm CO2/minute/gram). [However] the differences in [the] average rates of photosynthesis were not significantly different.”15
Another experiment compared the photoperiodic sensitivity of green-leafed (Perilla frutescens) and red-leafed (Perilla crispa) Perilla (A flowering Asian annual) or how long it took each of the Perilla plants to reach the same level of growth or flowering based on exposure to different light conditions. exposed to 8 hours of light, red-leafed Perilla took 4 days longer to reach the
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