Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase Activity

Abstract

(12,23,28).The effect of carbohydrate accumulation on the rate of dark respiration has received less attention but appears to have been consistently observed by a variety of approaches (2,6,29). The essential observation is that the rate of respiration is proportional to carbohydrate content or is stimulated by provision of exogenous carbohydrate. The implication is that the amount of respiration is regulated by substrate supply rather than demand for ATP or reducing equivalents. Indeed, it has been suggested that, under conditions of high carbohydrate supply, a substantial proportion of the reductant generated during carbohydrate catabolism may be consumed by the alternative oxidase without being linked to ATP production (3,15

Fumaric acid: an overlooked form of fixed carbon in Arabidopsis and other plant species

“…1). Similar results have been reported for starch accumulation in a wide variety of plant species, including Arabidopsis (Caspar et al 1985). Both fimmric acid (Fig.…”

“…In fret, fumaric acid levels can exceed starch and soluble sugar (sucrose, glucose and fructose) levels in Arabidopsis thaliana (Table 1) In addition, results presented here suggest that fiunaric acid maybe metabolically accessible and, like starch and soluble sugar, may fi.mction as a transient storage form of fixed carbon. For instance, pgnd mutants that can't make starch (Caspar et al 1985) accumulate higher levels of fumaric acid than wild-type plants (Fig. 3), suggesting that some of the photosynthate that would normally be used to make starch is instead being used to form fumaric acid in the mutant plants.…”

“…The finding, described in Fig. 3, that starch biosynthesis (pgml) mutants (Caspar et al 1985) accumulate higher levels of fi-unaricacid than wild-type plants when grown in a 12-h photoperiod suggests that some of the photosynthate that would normally be used to produce starch is instead being used to make furnaric acid in the mutant plants.…”

“…Thepgml mutant (Caspar et al 1985 Fumaric acid assays and identljkation. Fumaxic acid was extracted and derivatized to its corresponding dimethyl ester using a protocol designed for extraction and derivatization of fatty acids (Browse et al 1986).…”

“…As formation and metabolism of photoassimilates represents a key component of plant growth and metabolism, a large number of studies have been devoted to examining the factors regulating the accumulation of different photoassimilates (e.g. Stumpf and Burris 1981;Bieleski 1982;CaSpar et al 1985;Lin et al 1988; Portions of this document may be illegible in electronic image products. Images are produced from the best avaiiable original document.…”