PHOTOSYNTHESIS OF PEACH LEAVES: LIGHT ADAPTATION, LIMITING FACTORS AND SUGAR CONTENT

Photosynthetic capacities and photosynthetic limitations were studied in peach leaves from 1–3 month old seedlings adapted to high light (sun: 900 μmol photons m^-2 s^-1) and low light (shade: 300 μmol photons m^-2 s^-1).

Maximum photosynthetic rate of adult leaves depended on the irradiance applied during leaf development.
Leaves from sun plants were adapted to high light.
Leaves from shade plants were adapted to low light.
However, in both sun and shade leaves, a steady photosynthetic rate could not be observed under saturing light (900 μmol photons m^-2 s^-1) and saturing CO₂ concentration (900 vpm). Photosynthesis was progressively inhibited under these conditions: a decrease of 4% h^-1 and 9% h^-1 was observed in sun and shade leaves respectively.
The inhibition could not be attributed to stomatal regulation.
Photosynthesis measurement under low O₂ concentration (2%) revealed that photosynthesis in sun leaves was limited by ribulose-bisphosphate regeneration.
In shade leaves photosynthesis was not limited by ribulose-bisphosphate regeneration but was probably limited by triose-phosphates utilization.

In both sun and shade leaves maintained under 900 vpm CO₂ concentration during 4 hours, phloem loading rate was notably lower than photosynthetic rate since soluble sugars and starch accumulated.

Peach, XXIII IHC

J. Gaudillere, A. Moing

https://doi.org/10.17660/ActaHortic.1992.315.12