PARENT SESSION
Contributed Oral Session 28: Plant Physiology: Effects of Ozone CO2, and Cavitation
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal
Inter-vessel pitting and cavitation in vessels: a basis for a safety vs. efficiency trade-off in xylem transport.
Wheeler, James*,1, Sperry, John1, Hacke, Uwe1, Hoang, Nguyen 2, 1 University of Utah, Salt Lake City2 Tufts University, Boston
ABSTRACT- We tested the hypothesis that greater safety from cavitation by air-seeding through intervessel pits comes at the cost of less porous pit membranes with greater flow resistance. Over twenty vessel-bearing species with non-vestured pits from diverse angiosperms and one fern were compared. Unexpectedly, there was no relationship between pit resistance (and hence the prevailing membrane porosity) and cavitation pressure. There was, however, a strong inverse relationship between pit area per vessel and vulnerability to cavitation. This suggests that cavitation is caused by the rare largest membrane pore per vessel, the average size of which increases with total pit area per vessel. If safety from cavitation constrains pit membrane surface area, it also limits vessel surface area and the minimum vessel resistivity. This trade-off was consistent with an increase in vessel resistivity with increasing cavitation pressure. The trade-off was compensated for by a reduction in the percentage of vessel wall pitted: from as high as 16 % in vulnerable species to as low as 2% in resistant species. Across species, end-wall pitting accounted for roughly half of the total xylem resistivity. This fraction comes close to maximizing vessel conductivity if vessel surface area is constrained by total pit area for cavitation protection.
Key words: cavitation resistance, xylem structure and function, air-seeding, water transport