Comparative studies on photosynthetic characteristics of Notopterygium incisum and N. forbesii Comparison of photosynthetic characteristics between an endangered species Camellia pubipetala and its widespread congener C. sinensis Applications studies of the modified exponential model on photosynthesis—light response and CO2 response curves of Mirabilis jalapa Applications studies of the modified exponential model on photosynthesis—light response and CO2 response curves of Mirabilis jalapa