Specific leaf metabolic changes paving the way to osmotic potential in
four Quercus species in response to drought
Osmotic adjustment is recognized as an important mechanism of
maintaining turgor under water stress. However, the metabolic basis of
this process has been documented in some few forest tree species. The
leaf water relations of four Quercus species were studied from P-V
curves in well-watered (WW) and water-stressed (WS) seedlings. Lowest
values of osmotic potential at full turgor (Ψπ100) followed the ranking
Q. ilex < Q. faginea < Q. pyrenaica < Q.
petraea. The leaf osmotic potential at the turgor loss point (ΨTLP) kept
up with the patterns of the Ψπ100 across species and treatments. The
leaf metabolome pointed out to the pool of carbohydrates, some organic
acids, and cyclitols as main contributors to osmotic potential.
Amino-acids, although very reactive to WS particularly in Q. pyrenaica
accounted quantitatively less to osmotic potential than rest of the
compounds. The relevance of proto-quercitol was high as a contributor to
osmotic potential regardless treatment or species. Other metabolites as
quinic acid played a more relevant role in osmoregulation specifically
in Q. ilex. The study shows leaf osmotic potential is underpinned by a
metabolic response shaped according to phylogenetic history and ecology
of the species.