The effect of polyploidization on tree hydraulic functioning

• Published in: American journal of botany Vol. 105; no. 2; pp. 161 - 171
• Main Authors: De Baerdemaeker, Niels J. F., Hias, Niek, Van den Bulcke, Jan, Keulemans, Wannes, Steppe, Kathy
• Format: Journal Article
• Language: English
• Published: United States John Wiley and Sons, Inc 01-02-2018; Botanical Society of America, Inc
• Subjects: Acoustic emission; acoustic vulnerability curves; Botany; Capacitance; Cavitation; Dehydration; Desiccation; desorption curves; Diploidy; Drought; Drought resistance; drought stress; Drying; embolism; Flowers & plants; INVITED SPECIAL ARTICLE: For the Special Section: Wood: Biology of a Living Tissue; Malus; Malus - anatomy & histology; Malus - genetics; Malus - physiology; Moisture content; Parenchyma; Plant biology; Plant Shoots - anatomy & histology; Plant Shoots - physiology; Plant tolerance; Ploidy; Polyploidy; Shoots; Tetraploidy; Trees - anatomy & histology; Trees - genetics; Trees - physiology; Water - metabolism; Water content; Water deficit; water transport; Wood; Wood - anatomy & histology; xylem vulnerability; Polyploidy; drought stress; water transport; acoustic vulnerability curves; wood; desorption curves; embolism; xylem vulnerability; Malus
• ISSN: 0002-9122; 1537-2197
• DOI: 10.1002/ajb2.1032

Premise of the Study
Recent research has highlighted the importance of living tissue in wood. Polyploidization can impact amounts and arrangements of living cells in wood, potentially leading to increased drought tolerance. Tetraploid variants were created from the apple cultivar Malus ×domestica ‘Gala’ (Gala‐4x), and their vulnerability to drought‐induced cavitation and their hydraulic capacitance were compared to those of their diploid predecessors (Gala‐2x). Assuming a positive correlation between polyploidy and drought tolerance, we hypothesized lower vulnerability and higher capacitance for the tetraploid.
Methods
Vulnerability to drought‐induced cavitation and the hydraulic capacitance were quantified through acoustic emission and continuous weighing of shoots during a bench‐top dehydration experiment. To underpin the hydraulic trait results, anatomical variables such as vessel area, conduit diameter, cell wall reinforcement, and ray and vessel‐associated parenchyma were measured.
Key Results
Vulnerability to drought‐induced cavitation was intrinsically equal for both ploidy variants, but Gala‐4x proved to be more vulnerable than Gala‐2x during the early phase of desiccation as was indicated by its significantly lower air entry value. Higher change in water content of the leafy shoot, higher amount of parenchyma, and larger vessel area and size resulted in a significantly higher hydraulic capacitance and efficiency for Gala‐4x compared to Gala‐2x.
Conclusions
Both ploidy variants were typified as highly sensitive to drought‐induced cavitation, with no significant difference in their overall drought vulnerability. But, when water deficit is short and moderate, Gala‐4x may delay a drought‐induced decrease in performance by trading hydraulic safety for increased release of capacitively stored water from living tissue.