Xylem and phloem formation dynamics in Quercus ilex L. at a dry site in Southern Italy

Balzano, Angela (author), Čufar, Katarina (author), De Micco, Veronica (author)

Quercus ilex L. dieback has been recently reported at numerous Mediterranean sites. Wood and phloem formation dynamics and tree-ring series of anatomical traits can be used to evaluate growth conditions of trees. We monitored cambial activity in Q. ilex trees growing at a site in southern Italy in order to assess how xylem and phloem production are affected by harsh seasonal climatic variation during a dry year. We followed xylogenesis by counting the number of cambial cells and detecting the occurrence of post-cambial cells throughout the year. As phloem did not show clear growth rings and boundaries between them, we followed the development of phloem fibres—their morphological traits during development and the distance from the cambium served as a reference point to evaluate the phloem production during the year. We detected a multimodal pattern in cambial activity, with wood production in three periods of the year and consequent formation of intra-annual density fluctuations (IADFs). The lowest production of xylem cells was observed in the dry late spring and summer period (likely due to the low water availability), while the highest occurred in autumn (the wettest period). Although we could not differentiate between early and late phloem, the analysis of phloem traits was useful to follow the dynamics of phloem production, which is generally difficult in Mediterranean tree species. We found cambial production of phloem throughout the year, even in the periods without xylem production. The results showed that if tree growth was constrained by environmental limitations, the ratio between xylem to phloem cells decreased and, in the most severely affected trees, more cells were formed preferentially in the phloem compared to xylem. We also briefly report the way in which to solve technical problems with tissue preparation due to extreme hardness and to the peculiar structure of Q. ilex wood and outer bark.

• Language: English
• Keywords: cambial activity, holm oak, Quercus ilex L., Mediterranean forest, xylogenesis, phloemogenesis
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 15 str.
• Numbering: Vol. 12, iss. 2, art. 188
• PID: 20.500.12556/RUL-127787
• UDC: 630*8
• ISSN on article: 1999-4907
• DOI: 10.3390/f12020188
• COBISS.SI-ID: 50602243
• Publication date in RUL: 23.06.2021

Record is a part of a journal

• Title: Forests
• Shortened title: Forests
• Publisher: MDPI
• ISSN: 1999-4907
• COBISS.SI-ID: 3872166

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 07.02.2021

Secondary language

• Language: Slovenian
• Keywords: kambijeva aktivnost, črnika, Quercus ilex L., sredozemski gozd, ksilogeneza, floemogeneza

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P4-0015
• Name: Les in lignocelulozni kompoziti