WOOD FORMATION IN JUNIPERUS EXCELSA SSP. POLYCARPOS IN THE HIGH MOUNTAINS OF NORTH-EAST IRAN

Cambial activity and of xylem formation in Persian juniper (Juniperus polycarpos) were studied during the 2010 growth season in the high mountains of Chaharbagh, Gorgan, north-east Iran. Wood microcores were collected weekly from March till May and biweekly from June till September from four trees....

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Bibliographic Details
Published in:Journal of tropical forest science 2013-07, Vol.25 (3), p.421-428
Main Authors: Saderi, SM, Pourtahmasi, K, Oladi, R, Rathgeber, CBK
Format: Article
Language:English
Subjects:
Cambium
Cell growth
Growing seasons
Growth rings
Pine trees
Rain
Tracheids
Tree growth
Trees
Xylem
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Summary:Cambial activity and of xylem formation in Persian juniper (Juniperus polycarpos) were studied during the 2010 growth season in the high mountains of Chaharbagh, Gorgan, north-east Iran. Wood microcores were collected weekly from March till May and biweekly from June till September from four trees. Thin sections were cut and anatomical features of the developing and mature tracheids were observed, counted and measured along three radial files of the growing xylem. Monthly tree-ring increments were correlated with monthly mean temperature and total rainfall. The dormant cambium contained 2—3 cell layers adjacent to the last formed phloem fibres in the previous year. Cambial cell division began on the second week of April and terminated at the end of August. The maximum number of cambium cells (8—9) and the maximum daily growth rates of all trees were achieved around mid-June. Rainfall and temperature showed a strong positive and negative relation respectively with monthly tree-ring increment. As the study area is cool and semi-arid, cambial reactivation is controlled by temperature. However during the growing period, water availability is the main limiting factor for growth. Aktiviti kambium dan pembentukan xilem dalam Juniperus polycarpos dikaji di kawasan pergunungan Chaharbagh, Gorgan di timur laut Iran semasa musim pertumbuhan tahun 2010. Mikrokor kayu diambil daripada empat batang pokok setiap minggu dari bulan Mac hingga Mei dan setiap dua minggu dari bulan Jun hingga September. Keratan nipis dibuat dan ciri anatomi trakeid yang membesar serta yang matang diperhati, dikira dan diukur sepanjang tiga baris jejari xilem yang membesar. Pertambahan gelang pokok bulanan dikorelasikan dengan purata suhu bulanan serta jumlah hujan bulanan. Kambium yang dorman mengandungi 2—3 lapisan sel bersebelahan dengan gentian floem terakhir yang terbentuk pada tahun sebelumnya. Pembahagian sel kambium bermula pada minggu kedua bulan April dan berakhir pada akhir bulan Ogos. Bilangan maksimum sel kambium (8—9 sel) dan kadar pertumbuhan harian yang maksimum bagi kesemua pokok dicapai sekitar pertengahan bulan Jun. Hujan dan suhu masing-masing menunjukkan perhubungan positif dan negatif yang kuat dengan pertambahan gelang pokok bulanan. Memandangkan kawasan kajian ini dingin dan separa kontang, pengaktifan semula kambium adalah dikawal oleh suhu. Namun semasa tempoh pertumbuhan, air merupakan faktor pengehad yang utama.
ISSN:0128-1283