The activity of enzymes characteristic for C4-type photosynthesis was determined in different organs of two herbaceous plants: Reynoutria japonica Houtt. and Helianthus tuberosus L. The activity of phosphoenolpyruvate carboxylase (PEPC) was usually higher in the roots, some of the stem tissues and petioles in comparison to the leaf blades. The highest activity of malic enzymes (NAD-ME, NADP-ME) and phosphoenolpyruvate carboxykinase (PEPCK) was in the petioles and stem tissues of both plants and the lowest in the leaf blades and the pith of Helianthus tuberosus L. and M. Kocurek, J. Pilarski.
The content of chlorophylls (Chl) (a+b), total carotenoids (x+c), and the pigment ratios of Chl a/b and Chls to carotenoids (a+b)/(x+c) of green leaves of five C4 plants were determined and compared to those of C3 plants. The C4 plants were: Pacific and Chinese silvergrass (Miscanthus floridulus and Miscanthus sinensis), sugar cane (Saccharum officinarum) as well as feed and sugar maize (Zea mays). The three C3 plants were beech, ginkgo, and oak. C4 plants possess higher values for the ratio Chl a/b (3.4-4.5) as compared to the C3 plants (2.6-3.3). Sugar maize had the highest values for Chl a/b (4.04-4.70) and exceptionally high contents of total carotenoids and consequently lower values for the ratio of (a+b)/(x+c) (mean: 3.75 ± 0.6). During autumnal senescence also C4 plants showed a faster decline of Chl b as compared to Chl a yielding high values for Chl a/b of 6 to 8. Chlorophylls declined faster than carotenoids yielding low (a+b)/(x+c) values below 1.0.
Foliar δ13C values of Calligogum kozlovi and Haloxylon ammodendron ranged from -13.13 to -15.11 ‰, while those of the rest 11 species were in the range of -22.22 to -27.73 ‰. This indicates that two of 13 dominant plant species in the Qaidam Basin possess a C4 photosynthetic pathway. Significant differences were observed for the average foliar δ13C values between C3 or C4 plant communities, between grass and shrub communities, even between the same species derived from different sites. Precipitation accounted for the major part of the differences. and H. Chen ... [et al.].