Developmental Changes of the Photochemical Reflectance Index (PRI), Chlorophyll Fluorescence and Leaf Pigments Show the Adaptability of Trees to Local Environments

Abstract

For plants growing in parks and along the roadsides of a city, the environmental and seasonal regulation of growth, or photosynthesis, is seldom assessed. The phenology of plants may differ due to varying environments, which may result in different growth or adaptability to local environments. Therefore, we explored several assays and optical indicators of photosynthesis and stress in three tree species (Prunus yedoensis Matsum, Zelkova serrata Makino and Acer palmatum Thunb. ) and two herbaceous species (Artemisia princeps Pamp and Taraxacum officinale Weber)growing commonly in three local parks of Changwon city, a large industrial city in Korea. The photochemical reflectance index (PRI), chlorophyll fluorescence, and pigments including chlorophyll and the flavonoids of leaves were monitored over a growing season for two years to evaluate the adaptability of plants to local environments. The values of all measurements exhibited striking seasonal and regional changes. PRI values were closely timed with photosynthetic activity and the pigment formation of leaves, particularly in some tree species. For the tree species, the plants which had the low values of PRI during the active growing season showed low levels of both chlorophyll fluorescence and high level of flavonoid, indicating that these plants were experiencing low photosynthetic activity and the specific needs in growth and development were not sufficiently provided by the local environment. Our results indicate that PRI provided a clear optical indicator of plant adaptability to the local environment and may provide a useful metric of effective growth using remote sensing measurements. Furthermore, the periodic PRI measurement is encouraged to be included in the surveillance program for city plant management.