Seasonal fluctuations of starch in root and stem tissues of coppiced Salix viminalis plants grown under two nitrogen regimes

Abstract

Seasonal changes in starch were studied at the tissue and cellular levels in roots and stems of Salix viminalis L. cuttings. Cuttings were planted in pots containing sand and grown in a controlled environment chamber in which seasons were artificially induced by changes in temperature and photoperiod. Nitrogen was supplied at optimum and low rates, and during dormancy, one-half of the plants were decapitated. Starch concentrations in root and stem tissues were determined regularly during shoot extension growth, dormancy and resprouting after dormancy. We used light microscopy (LM) combined with image analysis (IA) to determine the cellular localization and amount of starch in different cell types of stem and root tissues. Chemical analysis confirmed that starch concentrations were lower in plants receiving a high-N supply rate than in plants receiving a low-N supply rate. In all plants, the highest concentration of starch was in the roots. Light microscopy and IA showed that starch accumulated mainly in the phloem and cortical cells of both root and stem tissues. Starch grains were also regularly found in ray parenchyma cells. The amount of starch as well as the size of the grains showed strong seasonal fluctuations. In both roots and stems, starch concentrations were highest during predormancy and lowest during periods of shoot extension growth. At the time of resprouting, root cells of decapitated plants were more depleted of starch than root cells of intact plants, supporting the hypothesis that starch reserves in roots are important during the early phase of resprouting in coppice systems.

Autumnal nitrogen nutrition affects the C and N storage and architecture of young peach trees

“…By contrast, soluble sugar concentrations were not affected by time or N supply. The relationship between autumn N uptake and TNC accumulation is still debated in the literature, and contrasting results have been published, sometimes relative to the same species (Bollmark et al 1999;Von Fircks and Sennerby-Forsse 1998;Cheng et al 2004).…”

“…Most studies to date have been limited to one of these aspects and have not provided an integrated insight into the tree response to N fertilisation. Tree response to applied N varies with tree N status, a point that was not adequately addressed by many prior experiments (Niederholzer et al 2001;Millard and Proe 1993) and could explain inconsistencies in the literature (Bollmark et al 1999;Niederholzer et al 2001;Von Fircks and Sennerby-Forsse 1998). Nitrogen status altered N uptake (Cheng et al 2002), TNC (Total Non structural Carbohydrates) accumulation (Cheng et al 2004) and the trade-off between growth and storage (Sanz Perez et al 2007;Gloser et al 2009) which is generally assumed to be mainly determined by plant phenology.…”

Short-term effects of nitrogen availability on wood formation and fibre properties in hybrid poplar

“…Primary N assimilation into amino acids has demonstrable effects on both N and C metabolism (Coruzzi 2003;Geiger et al 1996). For example, both young apple and willow trees respond to nitrogen application by reduced accumulation of non-structural carbohydrates such as starch (Cheng et al 2004;von Fircks and Sennerby-Forsse 1998). N-modulated gene expression has been well-investigated in the herbaceous plant model Arabidopsis thaliana (Scheible et al 1997;Schleible et al 2004;Wang et al 2003Wang et al , 2004, where it has been shown that genes involved in C metabolism are co-ordinately regulated in response to N availability (Palanchar et al 2004).…”

C depletion and tree dieback in young peach trees: a possible consequence of N shortage?

“…However, an N limitation does not only restrict C acquisition but also C expenses, because root respiration is proportional to N uptake (Bloom et al 1992;Reich et al 1998). The final outcome on tree TNC content at leaf fall is still a matter of discussion since contrasting results have been published, sometimes on the same species (Bollmark et al 1999;Von Fircks and Sennerby-Forsse 1998;Cheng and Fuchigami 2000;Cheng et al 2002). It is however admitted that reducing the N supply in autumn will increase the tree TNC content, unless it affects leaf senescence, which was probably the case in our study.…”