Comparison of photosynthesis and productivity of Gunnera tinctoria Molina (Mirbel) with and without the phycobiont Nostoc punctiforme L.
Article first published online: 28 APR 2006
Plant, Cell & Environment
Volume 12, Issue 9, pages 941–946, December 1989
How to Cite
OSBORNE, B. A. (1989), Comparison of photosynthesis and productivity of Gunnera tinctoria Molina (Mirbel) with and without the phycobiont Nostoc punctiforme L. Plant, Cell & Environment, 12: 941–946. doi: 10.1111/j.1365-3040.1989.tb01974.x
- Issue published online: 28 APR 2006
- Article first published online: 28 APR 2006
- Received 2 January 1989; received in revised form 25 May 1989; accepted for publication 21 June 1989
- Gunnera tinctoria;
- Nostoc punctiforme;
- photosynthetic productivity;
- nitrogen assimilation
Abstract. Marked increases in growth and nitrogen content were found with Gunnera tinctoria Molina (Mirbel) plants infected (+Nostoc) with the cyanobacterium Nostoc punctiforme L., in comparison to uninfected (—Nostoc) plants and this was attributed to N2-fixation by the phycobiont. Whilst host and symbiont can be grown separately, preliminary data indicates that the host plant is reliant on the cyanobacterium to meet its nitrogen requirements because it has little capacity to assimilate nitrate. Although the maximum light-saturated rate of photosynthesis was higher in the +Nostoc plants, there was no reduction in photosynthetic efficiency under lightlimiting conditions, despite marked differences in plant nitrogen status. Differences in photosynthetic rate were implicated as the major reason for the differences in plant productivity. Stomatal conductance was insensitive to changes in plant nitrogen status and did not parallel the variation in photosynthetic rates. The ecological significance of the largely invariant stomatal response and the consequences of differences in water and nitrogen-use efficiencies between + and —Nostoc plants is discussed.