The Comparative Study On Photosynthetic Physiological Characteristics Of Five Chinese Traditional Medicinal Herbs

This research was based on medicinal parts and photosynthetic characteristics and other aspects of different medicinal herbs so that Job's-tears (Coix lachryma-jobi), safflower(Carthamus tinctorius), corn mint(Mentha haplocalyx), Rehmannia glutinosa Libosch. and Araceae(Arisaema consanguineum) were chosen as experimental materials including normal and diseased leaves, leaves on plants with flowering detached and undetached. The changes of photosynthetic pigment content, net photosynthetic rate, transpiration rate and water use efficiency during the whole growing period, and the diurnal changes of photosynthesis in different ecological conditions were measured, and the changes of soluble sugar content, nitrate reductase activity, free amino acids content and soluble protein content were also determined simultaneously. The results showed that, Job's-tears, with seeds as its gain part, showed the highest photosynthetic pigment content, net photosynthetic rate, transpiration rate and water use efficiency during whole growing period in the five species of medicinal herbs, and its diurnal change of photosynthesis showed single peak curves without midday depression. Safflower, whose tubular-flowers and seeds were the main medicinal parts, had the shortest growing period among the five herbs. The changes of photosynthetic pigment content, net photosynthetic rate, transpiration rate and water use efficiency during growing period of safflower were all single peak curves, but its daily change of photosynthesis was double peak curve with a midday depression. With stems and leaves as its medicinal parts, corn mint had indefinite growth behavior, blossomed and fruited and grew in vegetative organs synchronously. The daily changes of photosynthesis were also two peak curves having midday depression although it was heliophillous plant. Rhizomes were the medicinal parts of Rehmannia glutinosa and tubers were the medicinal parts of Araceae, but Rehmannia glutinosa was heliophillous plant and Araceae was heliophibous so that the net photosynthetic rate of Rehmannia glutinosa was higher than that of Araceae. The changes of photosynthesis of the two species were double peak curves differing from those of the other three seeding-reproduced plants because of the existence of rhizomes and tubers during growing period. The determination of photosynthetic physiological parameters of bract of Areceae spadix during growing period showed that it contained photosynthetic pigment and, was capable of photosynthesis, transpiration, although lower than those of leaves. The photosynthetic physiological characteristics of diseased leaves of Rehmannia glutinosa were much lower than that of normal leaves.On the other hand, the substance metabolism of different medicinal herbs revealed diversity during different growing phases, in different species and different treatments. Carbohydrate (C) and nitrides (N) acted as mainphotosynthetic production and the ratio of them (C/N) showed variations obviously in different growing stages. Lower C/N in early stages showed enlargement metabolism, meaning that nutrition was used in the growth of vegetative organs such as roots, stems and leaves. Higher C/N in late stages showed storage metabolism, meaning that nutrition was used in the growth of fruits, seeds (such as in Job's-tears, safflower andcorn mint) orover-winter storage organs--rhizomes and tubers (such as in Rehmannia glutinosa andAraceae).