Intra-annual leaf phenology, radial growth and structure of xylem and phloem in different tree parts of Quercus pubescens
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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. To understand better the time course of leaf development and radial growth patterns in different tree parts, we studied leaf phenology and intra-annual xylem and phloem formation and 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. In addition, the xylem ring was wider than the phloem ring in all three parts. Thus, phloem ring widths in stem represented 24.8% and in branches 79.4% of the xylem ring width. Earlywood occupied 52.9% (stem) and 74.9% (branches) of the xylem ring, and early phloem 53.7% (stem) and 43.3% (branches) of the phloem ring. Most of the annual radial increment (i.e. xylem and phloem increments) in stem and branches was formed prior to full leaf development. Latewood and late phloem were formed in the period of full leaf unfolding. 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.
KeywordsPubescent oak Sub-Mediterranean climate Cambium Stem Branch Earlywood vessel
The authors gratefully acknowledge the help of Boštjan Zupanc, Adriana Podržaj and Tina Rus in the field and laboratory. We thank Zlatko Rojc for his permission to perform the study on the plot, and Martin Cregeen for language editing. We thank the reviewers for their valuable comments and suggestions, which improved the quality of the paper.
This work was supported by the Slovenian Research Agency, Young Researchers’ Program (Martina Lavrič), research core funding Nos. P4-0085 and P4-0107, Project J4-7203 (short- and long-term responses of oak in sub-Mediterranean region to extreme weather events using a tree anatomical analysis and ecophysiological measurements) and by the FP7 Capacities Project EUFORINNO (REGPOT No. 315985).
JG, ML and KE conceived and designed the work; ML, JG and KE collected the data; all authors analysed and interpreted the data; JG and ML drafted the manuscript; all authors critically revised the manuscript; all authors approved the final version of the manuscript to be published.
Compliance with ethical standards
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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