Annual changes in the concentration of minerals and organic compounds of Quercus suber leaves

Abstract

Mature leaves are the primary source of sugars, which give rise to many secondary metabolites required for plant survival under adverse conditions. In order to study the interaction of field-grown cork oak (Quercus suber L.) with the environment, we investigated the seasonal variation of minerals and organic metabolites in the leaves, using inductively coupled plasma atomic emission spectrometry, elemental analysis and nuclear magnetic resonance spectrometry. Statistical analysis showed that the data strongly correlated with seasonal climate and were divided in three groups corresponding to: (1) spring-early summer, (2) summer and (3) autumn-winter. The concentration of N, P, K and leaf ash content were highest in spring (recently formed leaves), reached the minimum during the hot and dry summer and increased slightly during the rainy period of autumn-winter. Conversely, Na, Mg and Ca concentrations were lowest in spring-early summer and increased during summer and autumn-winter, the Ca concentration increasing five-fold. Two cyclitol derivatives, quinic acid and quercitol were the major organic metabolites of the leaves. Their concentration along the season followed opposite trends. While quinic acid predominated during spring-early summer, when it contributed 12% to the leaf osmotic potential, quercitol was predominant during autumn-winter, when its contribution to leaf osmotic potential was about 10%. This different preponderance of the two compounds is expressed by the quercitol/quinic acid ratio, which can be as low as 0.2 in early summer and as high as 9 in winter. Sucrose and glucose concentrations also increased during autumn-winter. Evidence for the quercitol protective role in plants during stress is discussed, and on the basis of structural similarity, it is suggested that quinic acid could have an identical importance, with a protective role against heat and high irradiance. It is concluded that the marked changes in Q. suber leaf composition throughout the year could have important implications in the plant capacity to endure climatic stress.

Tree patch distribution drives spatial heterogeneity of soil traits in cork oak woodlands

“…Q. suber is a calcifugous tree that prefers acidic soils (Montero and Cañellas 1998); therefore, the lower leaf fall Mg content might be a strategy to cope with high levels of soil pH through decreasing the inputs of mobile cations to the soil. However, the low Mg concentration reported in the fresh leaves of these trees (Andivia et al 2010) in comparison with other studies (Oliveira et al 1996;Orgeas et al 2002;Passarinho et al 2006) suggests that the hypothesis of the Ca-Mg antagonistic effect is more realistic. This antagonist effect and its negative consequences on the nutritional status of cork oak trees point out the importance of a thorough assessment of soil conditions to assist in the detection of potential forest species best adapted to site-specific conditions.…”

Endogenously Synthesized (−)-proto-Quercitol and Glycine Betaine Are Principal Compatible Solutes ofSchizochytriumsp. Strain S8 (ATCC 20889) and Three New Isolates of Phylogenetically Related Thraustochytrids

“…Based on the data and considerations given above, we inferred that the unidentified signals of the 1 H and 13 C NMR spectra represented a species of cyclohexanepentol. Through a literature search, we found that these signals were in accordance with the NMR spectra of synthetic proto-quercitol (3,37,51) and extracted proto-quercitol from leaves of cork oak (47).…”

“…The assignments of the signals are marked on the spectra, i.e., compatible solute (Q or B) and atom (C or H) with the numberings given on the shown formulae of the compatible solutes. The assignments were based on previously published NMR data (3,16,37,47,51). The cells were grown in medium M1 with 1.0 M NaCl added.…”

“…In vitro experiments have shown that (ϩ)-proto-quercitol isolated from oak protects glutamine synthetase against heat inactivation in a concentration-dependent manner (30) and protects the cyclic photophosphorylation activity of isolated thylakoid membranes of spinach during a freeze and thaw cycle (45). Both stereoisomers of proto-quercitol have been linked to protection against cold-induced stress in cork oak (47) and drought-and salt-induced stress in species of eucalyptus (1,39).…”

Seasonal changes in carbohydrates, cyclitols, and water relations of 3 field grown Eucalyptus species from contrasting taxonomy on a common site

“…The cyclitol "quercitol" is commonly detected in species of Quercus (Passarinho et al, 2006;Popp et al, 1997) and may contribute to osmotic relations in some species of Eucalyptus (Merchant et al, 2005;. Quercitol is found in significant concentrations in Eucalyptus spp.…”