Seasonal changes of δD and δ18O in tree-ring cellulose of Quercus crispula suggest a change in post-photosynthetic processes during earlywood growth. (15th June 2018)

• Record Type: Journal Article
• Authors: Nabeshima, Eri; Nakatsuka, Takeshi; Kagawa, Akira; Hiura, Tsutom; Funada, Ryo
• Editors: Mencuccini, Maurizio
• Is Part Of: Tree physiology. Volume 38:Number 12(2018)
• Page Start: 1829
• Page End: 1840
• Publication Date: 2018-06-15
• Subjects: annual ring -- deciduous broad-leaved tree -- hydrogen -- isotope ratios -- oxygen -- relative humidity -- ring-porous tree -- starch; Trees -- Physiology -- Periodicals; 582.16
• DOI: 10.1093/treephys/tpy068
• Languages: English
• ISSNs: 0829-318X

Abstract

Abstract: Leaf photosynthetic and post-photosynthetic processes modulate the isotope ratios of tree-ring cellulose. Post-photosynthetic processes, such as the remobilization of stored starch in early spring, are important to understanding the mechanisms of xylem formation in tree stems; however, untangling the isotope ratio signals of photosynthetic and post-photosynthetic processes imprinted on tree rings is difficult. Portions of carbon-bound hydrogen and oxygen atoms are exchanged with medium water during post-photosynthetic processes. We investigated the δD and δ 18 O values of tree-ring cellulose using Quercus crispula Blume trees in two different habitats to evaluate seasonal changes in the exchange rate ( f -value) of hydrogen or oxygen with medium water, and examined the associations of the post-photosynthetic processes. Theoretically, if the f -value is constant, δD and δ 18 O would be positively correlated due to meteorological factors, while variation in the f -value will create a discrepancy and weak correlation between δD and δ 18 O due to the exchange of carbon-bound hydrogen and oxygen with medium water. The values of δD decreased drastically from earlywood to latewood, while those of δ 18 O increased to a peak and then decreased toward the latewood. The estimated seasonal f -value was high at the beginning of earlywood and decreased toward the latewood. The post-photosynthetic processes associated with changes in the f -value were the remobilization of stored starch and triose cycling during cellulose synthesis because of the shortage of photo-assimilates in early spring. Although we did not evaluate relevant physiological parameters, the seasonal pattern of δD and δ 18 O in tree-ring cellulose of Q. crispula was clear, suggesting that the dual isotope (δD and δ 18 O) approach can be used to reveal the resource allocation mechanisms underlying seasonal xylem formation.