CHANGES OF PHOTOSYNTHETIC CHARACTERISTICS IN WATER-STRESSED ´RANCOCAS´ BLUEBERRY LEAVES

Photosynthetic characteristics of ‘Rancocas’ highbush blueberry (Vaccinium corymbosum) leaves were monitored under well-watered and water-stressed conditions.
Two-year-old trees in 4-L pots were daily irrigated (well-watered) or not irrigated for 7 days (water-stressed). Soil water potentials in well-watered and water-stressed conditions were measured to be approximately -0.22 and -0.99 MPa, respectively, whereas leaf water potentials in well-watered and water-stressed blueberries were about -1.07 and -1.79 MPa, respectively.
The CO₂ assimilation rates of well-watered and water-stressed blueberries were both saturated at about 500 &micromol m^-2 s^-1 photosynthetic photon flux density (PPFD) following the initial linear increases with increasing PPFD up to about 200 µmol m^-2 s^-1. Well-watered blueberry exhibited higher CO₂ assimilation rate than the water-stressed blueberry by 3-5µmol m^-2 s^-1 depending on PPFD ranged from 0 to 2,000µmol m^-2 s^-1. Maximum CO₂ assimilation rates of well-watered and water-stressed blueberries were 8.8 and 4.6µmol m^-2 s^-1, respectively.
Apparent quantum yield appeared to be similar in well-watered and water-stressed blueberries, but both light compensation point and dark respiration rate were higher in water-stressed blueberry.
Net CO₂ assimilation rates during the day were always higher in well-watered than in water-stressed blueberry.
In water-stressed blueberry, the diurnal time course of net CO₂ assimilation rate showed a sustained decrease until midday followed by afternoon recovery.
However, such change was less apparent in well-watered blueberry.
Stomatal conductance and transpiration rate during the day were always higher in well-watered than in water-stressed blueberry, being decreased until midday and then increased.
Their diurnal changes were more apparent in well-watered than in water-stressed blueberry.
However, the differences in stomatal conductance and transpiration rate between well-watered and water-stressed blueberries were diminished until midday and then became larger thereafter.

VIII International Symposium on Vaccinium Culture

H.J. Lee, S.J. Kim, D.J. Yu, B.Y. Lee, T.C. Kim

CO₂ assimilation, dark respiration, photoinhibition, quantum yield, stomatal conductance, transpiration

https://doi.org/10.17660/ActaHortic.2006.715.15