Optical properties and the content of photosynthetic pigments in the stems and leaves of the apple-tree
2005
Tokarz, K. | Pilarski, J.,Polish Academy of Sciences, Krakow (Poland). F. Gorski Inst. of Plant Physiology
Optical properties of stems change with their age. Light reflectance of current year stems equalled 14.2 percent, while the one for 3-year-old stems decreased to 10.2 percent, absorption for the current year stems equalled 55.5 percent and increased up to 66.4 percent for 3-year-old ones. Light transmittance for the cork of current year stems equalled 30.2 percent, and decreased with the age of stems reaching 23.4 percent for the 3-year-old ones. The cork transmitted less than 5 percent of light of 400 nm, but the transmittance increased with the increase in the wavelength up to 55 percent at 700 nm. The reflectance of light by the leaf equalled 6.9 percent, absorption 89.7 percent, and transmittance 3.4 percent. In August the highest amount of chlorophyll pigments (6.2 mg/square dm) and carotenoids (1.63 mg/square dm) was detected in the leaves of the apple-tree, however, the ratio of chl a/b reached the highest value 4.12 in June. For the bark of apple-tree stems the content of chlorophyll pigments increased since spring and reached the maximum content of about 2.8 mg(chl)/square dm for 1-3-year-old stems in the summer months, while for the current year stems in October. The ratio chl a/b was at the same level, about 2.2 during the whole year. The content of carotenoids was lower in stems than in leaves and was at the similar level during the year, however, it increased with the age of stems. Minor changes in the optical properties and the content of photosynthetic pigments occurring with the age of stems may be due to the low increment in cork thickness in the studied age groups of plants
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