title: Localized cooling of stems induces latewood formation and cambial dormancy during seasons of active cambium in conifers.
abstract: OBJECTIVE
  In temperate regions, trees undergo annual cycles of cambial growth, with periods of cambial activity and dormancy. Environmental factors might regulate the cambial growth, as well as the development of cambial derivatives. We investigated the effects of low temperature by localized cooling on cambial activity and latewood formation in two conifers, Chamaecyparis obtusa and Cryptomeria japonica.
  
  
  METHODS
  A plastic rubber tube that contained cooled water was wrapped around a 30-cm-wide portion of the main stem of Chamaecyparis obtusa and Cryptomeria japonica trees during seasons of active cambium. Small blocks were collected from both cooled and non-cooled control portions of the stems for sequential observations of cambial activity and for anatomical measurements of cell morphology by light microscopy and image analysis.
  
  
  RESULTS
  The effect of localized cooling was first observed on differentiating tracheids. Tracheids narrow in diameter and with significantly decreased cambial activity were evident 5 weeks after the start of cooling in these stems. Eight weeks after the start of cooling, tracheids with clearly diminished diameters and thickened cell walls were observed in these stems. Thus, localized low temperature induced narrow diameters and obvious thickening of secondary cell walls of tracheids, which were identified as latewood tracheids. Two months after the cessation of cooling, a false annual ring was observed and cambium became active again and produced new tracheids. In Cryptomeria japonica, cambial activity ceased earlier in locally cooled portions of stems than in non-cooled stems, indicating that the cambium had entered dormancy sooner in the cooled stems.
  
  
  CONCLUSIONS
  Artificial cooling of stems induced latewood formation and cessation of cambial activity, indicating that cambium and its derivatives can respond directly to changes in temperature. A decrease in the temperature of the stem is a critical factor in the control of cambial activity and xylem differentiation in trees.
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, Faculty of Agriculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
authors.forename: Shahanara
authors.initials: S
authors.lastname: Begum
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, Institute of Wood Technology, Akita Prefectural University, Noshiro-Akita 016-0876, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Kudo
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan.
authors.forename: Yugo
authors.initials: Y
authors.lastname: Matsuoka
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakaba
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, Faculty of Agriculture, Hokkaido University, Sapporo 060-8589, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamagishi
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, Faculty of Agriculture, Ehime University, Matsuyama-Ehime 790-8566, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Nabeshima
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan.
authors.forename: Md Hasnat
authors.initials: MH
authors.lastname: Rahman
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, Faculty of Forestry, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia.
authors.forename: Widyanto Dwi
authors.initials: WD
authors.lastname: Nugroho
authors.affiliation: Tohoku Regional Breeding Office, Forestry and Forest Products Research Institute, Takizawa-Iwate 020-0173, Japan and.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Oribe
authors.affiliation: College of Life Sciences, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Hyun-O
authors.initials: HO
authors.lastname: Jin
authors.affiliation: Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan, College of Life Sciences, Kyung Hee University, Yongin 446-701, Korea funada@cc.tuat.ac.jp.
authors.forename: Ryo
authors.initials: R
authors.lastname: Funada
mesh_terms: D000388:Air; D058506:Cambium / Q000502:physiology*; D029780:Chamaecyparis / Q000502:physiology; D003080:Cold Temperature; D032485:Cryptomeria / Q000502:physiology; D018547:Plant Stems / Q000502:physiology*; D012621:Seasons; D064028:Tracheophyta / Q000502:physiology*; D014934:Wood / Q000502:physiology*
keywords: Chamaecyparis obtusa; Cryptomeria japonica; cambial dormancy; false ring; latewood formation; localized cooling of stem