INFLUENCE OF SOIL WATER LEVELS ON ASSIMILATION AND WATER USE EFFICIENCY IN HAZELNUT.

A. Tombesi
Hazelnut trees were grown under water regimes of 1) 90% available water, 2) 65% available water and 3) values decreasing to the wilting point.

In conditions of warm temperature and intense light, the leaf photosynthesis of non-stressed trees was highest at 9:00h, with an inflection at 12:00h and a recovery at 16:00h.

On trees under water stress, photosynthesis decreased during the day and continuously decreased as water availability approached the wilting point. Photosynthesis remained at high level till 60% available water, then it decreased strikingly.

Transpiration and stomatal conductance are correlated with photosynthesis, while the intercellular CO2 concentration remains constant. On leaves under water stress, there was a low quanta efficiency with reduction of energy transporter enzymes and of those governing CO2 fixation.

Water use efficiency decreased during the day and it was constant till 60% available water, after which, it decreased to lower values.

On water stressed leaves, chlorophyll, soluble sugars and starch decreased. On efficient trees, the highest water use was about 2 liters per day and per leaf square meter.

Nearly 45% of the water loss was due to stomatal transpiration, 35% to non-stomatal transpiration and 20% to soil evaporation.

Therefore, to obtain the highest assimilation by the leaves, the soil water content must be over 60% field capacity, but not too much or water will be lost.

Soil water loss should be controlled because it is an important part of total water use.

Tombesi, A. (1994). INFLUENCE OF SOIL WATER LEVELS ON ASSIMILATION AND WATER USE EFFICIENCY IN HAZELNUT.. Acta Hortic. 351, 247-256
DOI: 10.17660/ActaHortic.1994.351.25
https://doi.org/10.17660/ActaHortic.1994.351.25

Acta Horticulturae