Seasonal fluctuations of low‐molecular‐weight sugars, starch and nitrogen in sapwood of Pinus sylvestris L.

Abstract

The content of water-soluble substances and starch in the living tree stem at the time of felling influences wood durability during further utilization. The aim of the study was to describe the annual and seasonal fluctuations in the contents of stored carbohydrates and nitrogenous compounds. The contents of soluble sugars, starch, and nitrogen were measured in the outer sapwood (0-15 mm from cambium) of 65-yr-old Scots pine {Pinus sylvestris L.) trees during an annual cycle. To study the influence of growth conditions, samples were taken from different stands in Sweden, in one stand from a control and a fertilized block. The effect of the age of the trees on the content of stored substances was also considered by comparing young (10-15 yrs old) and older trees (40-65 yrs old). Determination of the carbohydrates was carried out using enzymatic analysis. The outer pine sapwood contained a higher content of low-molecular weight sugars during autumn and winter than during spring and summer. Starch content rose at the beginning of the growth period and decreased in autumn. The content of soluble sugars increased towards the cambium on all sampling occasions. Fructose and glucose were dominant sugars in all the stands studied. Seasonal changes of sucrose were different from those of glucose and fructose, in that the sucrose content was already decreasing in February. The variations in the nitrogen content of the sapwood were far smaller than those of the soluble sugars. No significant differences were found between the stands with regard to glucose, fructose and the sum of all three sugars. The fertilized block showed low content of sucrose and nitrogen. It is concluded that seasonal fluctuations are more important with regard to the sugar content than the effect of growth conditions. Data indicate a lower content of soluble sugars and nitrogen in the outermost sapwood of young trees as compared with older trees.

Nonstructural Carbon in Woody Plants

“…Similar seasonal trends have been observed in drought-deciduous trees in semiarid climates, where stemwood NSC concentrations decrease during leaf expansion and reproduction and are higher during the dry season than during the wet season (92,149). In evergreen conifers, NSC declines sharply from the sapwood to hardwood, concentrations of sugars are higher during winter than during summer, and starch peaks at the beginning of the growing season (34,128). In deciduous conifers, seasonal variations are smaller and similar to those in diffuse-porous trees (48).…”

“…If we focus specifically on these pools, NSC concentrations are highest near the cambium or in young sapwood and are higher in temperate deciduous species than in evergreen species (48,149). With increasing tree age and/or height, NSC concentrations in stem wood generally remain stable or increase (41,98,111,128). In mature deciduous trees, NSC amounts, the NSC fraction allocated to starch versus sugar, and their seasonal fluctuations are higher in ring-porous trees (e.g., Quercus).…”

Do trees use reserve or newly assimilated carbon for their defense reactions? A 13C labeling approach with young Scots pines inoculated with a bark-beetle-associated fungus (Ophiostoma brunneo ciliatum)

“…The 13 C labeling-technique allowed to label C stored during August after cessation of shoot growth and early wood formation [27,46]. Our results show that three weeks after inoculation, sapwood and phloem tissues of saplings were highly enriched in 13 C as compared to unlabeled ones.…”

Changes of carbon and nitrogen metabolites in white spruce (Picea glauca [Moench] Voss) of contrasted growth phenotypes

“…Most organs investigated showed a decrease in starch concentrations in the summer, with current-year needles and stems having the most extensive depletion. Previous observations made with young and mature Scots pine trees under natural declining photoperiod also highlighted a marked decrease of starch concentrations in current-year needles between July and September (Mandre et al 2002;Oleksyn et al 2000;Terziev et al 1997). Soluble sugars are known to constitute most of the carbohydrate pool of the needles and roots of young black spruce (Picea mariana (Mill.)…”