The gas exchanges of two cropping kiwifruit vines, which had been growing
for 7 years on two scale lysimeters at the Udine University Experimental Farm, were
recorded during a deep water stress/rewatering cycle between 72 and 87 DAFB. The
instantaneous carbon and water exchanges were recorded on one heavily cropping
and one lightly cropping vine. Crop loads were adjusted at 26 DAFB. Carbohydrate
contents of fruits were followed during the study. The daily carbon uptake of the
high-cropping vine was consistently higher (>30%) than the low-cropping one, both
in absolute terms, and in terms of unit leaf area. Transpiration, on the other side,
was higher in the low-cropping vine, in virtue of a 30% greater leaf area, probably
resulting from the greater availability of resources for vegetative growth in this vine.
When expressed in normalised terms (moles/leaf area) in fact, transpiration between
the two vines appeared much more similar, although still slightly higher in the lowcropping
one. Water shortage appeared to modify the fruit carbohydrates profile by
increasing the glucose/fructose ratio, with the heavy-crop vine exhibiting a higher
glucose content. On the contrary, the hexoses/sucrose ratio was reduced as a
consequence of the water shortage, particularly in the low-crop plant.
