Diurnal-Nocturnal Changes in the Starch of Tobacco Leaves

Abstract

The quantitative changes in starch in tobacco leaves have been determined over diurnal-nocturnal periods for rapidly expanding, fully expanded, and yellow leaves. The daily increase in starch lessens as the leaves mature and senesee, and the amount of stureh not undergoing diurnal variation in fully expanded leaves is more than in rapidly expanding leaves.

Metabolic flux analysis of the non-transitory starch tradeoff for lipid production in mature tobacco leaves

“…Our finding that WT tobacco leaves accumulate large amounts of non-transient starch with plant age sheds new insight on the understanding of foliar starch regulation in a canopied crop as a divergence from the commonly accepted diurnal paradigm. While excess starch accumulation due to sink limitations ( Arp, 1991 ) is a particularly relevant concern in the case of a crop like tobacco that has been bred for leafy biomass production rather than seed yield, starch accumulation persisting at dawn in mature leaves was observed across a range of different pot sizes and has even been reported for field-grown tobacco ( Matheson and Wheatley, 1963 ), suggesting that this phenomenon is not solely attributable to limitations inherent in the growth conditions used in the current study. Indeed, we have also observed starch accumulation in non-mesophyll tissues of older tobacco plants at dawn and similar observations in Arabidopsis ( Lauxmann et al, 2016 ) have generated hypotheses about reproductive growth.…”

“…Diel patterns of foliar starch accumulation and degradation similar to Arabidopsis are understood to be the standard model of starch regulation due to their wide occurrence in many crop species including Beta vulgaris , Phaseolus vulgaris ( Fondy and Geiger, 1982 ), Spinacia oleracea ( Stitt et al, 1983 ), Zea mays ( Kalt-Torres and Huber, 1987 ), and Solanum tuberosum ( Lorenzen and Ewing, 1992 ). Less common have been reports that starch accumulates with plant age and persists at the end of the night in the leaves of a few plant species such as Nicotiana tabacum and Lotus japonicus ( Häusler et al, 1998 ; Matheson and Wheatley, 1963 ; Vriet et al, 2010 ). Starch persistence at daybreak, however, does not inherently suggest non-transient starch accumulation as it may simply be a consequence of delayed starch turnover under long photoperiods ( Matt et al, 1998 ), nutrient stresses ( Morcuende et al, 2007 ; Rufty et al, 1988 ), or sink-limited conditions ( Grimmer et al, 1999 ; Hädrich et al, 2012 ; Pilkington et al, 2015 ; Scialdone et al, 2013 ).…”

Theoretical and experimental approaches to understand the biosynthesis of starch granules in a physiological context

“…Some grasses partition only a low percentage of photoassimilates into leaf starch and store carbohydrates in the form of sucrose or fructans in the vacuoles of mesophyll cells (Trethewey and Smith 2000). In tobacco, the magnitude of diurnal changes in leaf starch content lessens with leaf maturation, and fully expanded leaves retain relatively high levels of starch during day and night (Matheson and Wheatley 1963), suggesting a lower demand of starch reserves at this developmental stage.…”

Diurnal Variation in Nonstructural Carbohydrates, In Vitro Digestibility, and Leaf to Stem Ratio of Alfalfa1

“…Starch contents of other plant parts underwent very little diurnal variation. Matheson and Wheatley (1963) described diurnal variations in starch content of rapidly expanding, fully expanded, and matured yellow tobacco lelVes. The daily increase and decline in starch lessened as leaves matured and senesced.…”