Distribution and utilization of assimilated carbon in red clover during the first year of vegetation
- 45 Downloads
The pattern of distribution of14C labelled assimilates and translocation with time was measured in red clover during one reproductive cycle. Measurements were made on whole plants grown outdoors in pots by exposing the aerial parts to14CO2 during one photoperiod. Simultaneously, root respiration and N2 fixation were recorded.
At the beginning of the vegetative period, 2/3 of the assimilates remained in the leaves (basal leaves), and 1/3 were directed to the root system. Then the development of branches required as much as 40% of the C and the root allocation decreased. Reproductive structures diverted 17% of the current photosynthates. Nitrogen fixation was optimal during the maximum extension of the basal leaves and decreased during the development of branches. During this period, C allocation to the nodulated roots was high with an estimated amount of 3.2 mg of C per mg of N fixed.
With time, translocation occured within the foliage, from basal leaves to the leaves of the branches and to the new basal leaves developed after senescence of the branches. Remobilization to the reproductive structures remained minimal indicating that flower and seed growth was supported by current photosynthesis.
Key wordsAssimilates distribution14CO2 labelling C remobilization N2 fixation Respiration costs Trifolium pratense L.
Unable to display preview. Download preview PDF.
- 1.Dobrenz A K and Massengale M A 1966 Change in carbohydrates in alfalfa (Medicago sativa L.) roots during the period of floral initiation and seed development. Crop. Sci. 6, 604–607.Google Scholar
- 3.Hodgkinson K C 1969 The utilisation of root organic compounds during the regeneration of lucerne. Aust. J. Biol. Sci. 22, 1113–1123.Google Scholar
- 4.Minchin F R, Summerfield R J, Hadley P and Rawstorne S 1981 Carbon and nitrogen nutrition of nodulated roots of grain legumes. Plant Cell Environ. 4, 5–26.Google Scholar
- 5.Pate J S 1977 Functional biology of dinitrogen fixation by legumes.In A Treatise on Dinitrogen Fixation, section III, Eds. R W F Hardy and W S Silver. 473 p. John Wiley, New York.Google Scholar
- 6.Ryle G J A, Powell C E, and Gordon A J 1981 Assimilate partitioning in red and white clover either dependant on N2 fixation in root nodules or utilizing nitrate nitrogen. Ann. Bot. 47, 515–523.Google Scholar
- 7.Salsac L, Drevon J J, Zengbe M, Cleyet-Marel J C and Obaton M 1984 Energy requirement of symbiotic nitrogen fixation. Physiol. Veg. 22, 509–521.Google Scholar
- 8.Smith D 1962 Carbohydrate root reserve in alfalfa, red clover and birdsfoot trefoil under several management schedules. Crop Sci. 2, 75–78.Google Scholar
- 9.Smith L H and Martin G C 1970 Foliar regrowth of alfalfa utilizing14C labelled carbohydrates stored in roots. Crop Sci. 10, 146–150.Google Scholar
- 10.Warembourg F R 1983 Estimating the true cost of dinitrogen fixation by nodulated plants in undisturbed conditions. Can. J. Microbiol. 29, 930–937.Google Scholar
- 11.Warembourg F R, Haegel B, Fernandez M P and Montange D 1984 Distribution et utilisation des assimilats carbonés en relation avec la fixation symbiotique d'azote chez le soja (Glycine max L. Merrill). Plant and Soil 82, 163–178.Google Scholar
- 12.Warembourg F R, Montange D and Bardin R 1982 The simultaneous use of14CO2 and15N2 labelling techniques to study the carbon and nitrogen economy of legumes grown under natural conditions. Physiol. Plant. 56, 46–55.Google Scholar