Intra-annual variations in leaf development, radial growth, including the phloem part, and sap flow have rarely been studied in deciduous trees from drought-prone environments. Here, we monitored leaf phenology, xylem and phloem formation and sap flow in Quercus pubescens from abandoned karst grasslands in Slovenia during the growing season of 2014. We found that the initial earlywood vessel formation started before bud opening at the beginning of April. Initial earlywood vessels were fully lignified and ready for water transport before full leaf unfolding at the end of May, indicating that they are essential to provide hydraulic conductivity for axial water flow during leaf development. Similar early spring patterns of xylem sap flow and LAI denoted that water transport in oaks broadly followed canopy leaf area development. In the initial three weeks of radial growth, phloem growth preceded that of xylem, indicating its priority over xylem at the beginning of the growing season. This may be related to the fact that after bud break, the developing foliage is a very large sink for carbohydrates but, at the same time, represents a small transpirational area. Whether the interdependence of the chronological sequence of the studied processes is fixed in Q. pubescens needs to be confirmed with more data and several years of analyses, although the ‘correct sequence’ of processes is essential for synchronized plant performance and response to environmental stress.
COBISS.SI-ID: 4701350
Basic knowledge of the intra-annual timings of leaf development and radial growth (including the phloem part) in different tree parts is generally missing although such rudimentary data are crucial to link the structure and function of vascular tissues at the whole tree level. For this purpose, we studied leaf phenology, intra-annual xylem and phloem formation and their structure in the stem and at two locations in branches of sub-Mediterranean Quercus pubescens in 2015. Onset and end dates of cambial cell production were synchronized at the two locations in branches, but were different at the stem base. The period of cell production was thus a month longer in the stem, resulting in 82.8 % and 45.1 % wider xylem and phloem increments, respectively. Phloem ring widths in stem represented 24.8 % and in branches 79.4 % of the xylem ring width. Most of the annual radial increment (i.e. xylem and phloem) in stem and branches was formed prior to full leaf development. Our study confirmed that the temporal sequence of leaf development and radial growth are not contemporary in Q. pubescens. Different intra-annual patterns of radial growth in different tree parts result in different structures of xylem and phloem, which is in line with different roles of stem and branches in terms of tree functioning.
COBISS.SI-ID: 4833190
Non-structural carbohydrates (NSCs, i.e., starch and soluble sugars) are frequently quantified in the context of tree response to stressful events (e.g., drought), because they serve as a carbon reservoir for growth and respiration, as well as providing a critical osmotic function to maintain turgor and vascular transport under different environmental conditions. We investigated the impact of soil water availability on intra-annual leaf phenology, radial growth dynamics and variation in NSC amounts in the stem of pubescent oak (Quercus pubescens Willd.). from a sub-Mediterranean region. For this purpose, trees growing at two nearby plots differing in bedrock and, consequently, soil characteristics (F-eutric cambisol on eocene flysch bedrock and L-rendzic leptosol on paleogenic limestone bedrock) were sampled. Non-structural carbohydrates were analysed in outer xylem and living phloem (separately for non-collapsed and collapsed parts). Results showed that xylem and phloem increments were 41.6 % and 21.2 %, respectively, wider in trees from F plot due to a higher rate of cell production. In contrast, the amount of NSCs and of soluble sugars significantly differed among the tissue parts and sampling dates but not between the two plots. Starch amounts were the highest in xylem, which could be explained by the abundance of xylem parenchyma cells. Two clear seasonal peaks of the starch amount were detected in all tissues, the first in September%November, in the period of leaf...
COBISS.SI-ID: 5196710
Our research focused on the influence of climatic factors on wood-anatomical features of pubescent oak (Quercus pubescens Willd.), which is one of the dominant native tree species in Slovenian sub-Mediterranean climate. In the period 2009%2014 we studied relationship between various wood-anatomical parameters (xylem ring width, early- and latewood widths, diameter, area and number of earlywood vessels) and climatic factors (precipitation, temperature and soil water content). In addition, we checked whether the studied wood-anatomical parameters contained complementarity or redundant climatic information in pubescent oak at Podgorski Kras. Preliminary results showed that studied parameters were mainly related to temperature. In period before and at the onset of cambial activity (i.e. January%May), earlywood width and earlywood vessel area were positively related to the maximum temperature, whereas number of earlywood vessels and xylem ring width were positively related to the mean temperature. This indicates that weather conditions in this period have a significant impact on hydraulic properties of xylem. For latewood width, we found significant correlation with temperature in summer months and for earlywood vessels with the temperature in period January%April. We could not confirm the impact of precipitation on xylem ring development. We concluded that latewood width and earlywood vessel characteristics are promising wood-anatomical parameters containing complementary information on the impact of weather conditions on radial growth of pubescent oak. However, it is necessary to emphasize that our analysis has been performed in a relatively short time period, therefore long-term data are needed for more reliable assessment of the applicability of the selected wood-anatomical parameters to dendroclimatological studies.
COBISS.SI-ID: 4637094
In the paper, most recent anatomical studies in bark are presented. Main reasons for smaller interests in barkanatomy studies compared to wood are listed. Seasonal dynamics of phloem formation in trees from temperate and Mediterranean climate as well as influence of environmental conditions on the structure of phloem increments are described. Link between phloem and wood increments in trees of different vitality is shown. Finally, impact of numerous secondary changes, occurring in the bark, on dendrometer measurements is discussed.
COBISS.SI-ID: 4819878