Carbon assimilation, partitioning and export in mature cladophylls of two asparagus (Asparagus officinalis) cultivars with contrasting yield

Abstract

To assess the physiological aspects underpinning cultivar difference in asparagus (Asparagus officinalis L.) yield, diel carbon exchange, carbon partitioning and export and sucrose phosphate synthase (SPS) activity were examined in mature cladophyll tissue of two asparagus cultivars (ASP-69 and ASP-03) under field conditions. Both cultivars exhibited similar diel patterns in carbon exchange rate (CER) and carbohydrate partitioning. Rates of carbon export estimated from CER and dry mass changes were the highest at midday and coincided with maximum assimilation rate. Carbon export accounted for about 74% of carbon fixation during the photoperiod. No diel fluctuations were observed in SPS activity in either cultivar. A positive correlation between day CER and carbon export rate (r2 = 0.87) was found and this relationship did not differ between the two cultivars studied. The greater carbon export rate measured in the high-yielding cultivar (ASP-69) was associated with significantly higher CER in comparison to the low-yielding cultivar (ASP-03). However, a correlation between sucrose concentration and carbon export rate did not exist. Biochemical evidence indicated that the greater CER in ASP-69 was associated with a significantly greater SPS activity (P 0.05). Phloem 14C exudate analysis revealed that 14C flux out of cladophyll tissue in ASP-69 was significantly greater than in ASP-03. These results indicate a feed-forward effect of rate of photosynthesis on assimilate export in the two cultivars studied.

Effect of aluminium on metabolism of starch and sugars in growing rice seedlings

“…Among sucrose metabolizing enzymes, sucrose synthase (SS, EC 2.4.1.13) and invertase (EC 3.2.1.26) are involved in cleavage of sucrose whereas the enzyme sucrose phosphate synthase (SPS, EC 2.4.1.14) solely catalyzes sucrose biosynthesis (Guo et al 2002). The initial step in breakdown of sucrose is achieved by either invertase or sucrose synthase.…”

Infection of post-harvest peaches by Monilinia fructicola accelerates sucrose decomposition and stimulates the Embden–Meyerhof–Parnas pathway

“…Acid invertase (AI), neutral invertase (NI), and sucrose synthase-cleavage (SS-cleavage) are the major enzymes responsible for sucrose decomposition 13 . Sucrose synthesis is catalyzed by synthase-synthesis (SS-synthesis) and sucrose phosphate synthase (SPS) 14 . Our previous studies on peach fruit demonstrated that low temperature stress causes a sharp decline in sucrose levels due to increased NI and AI activities 15 , if higher sucrose concentrations can be maintained, peaches are more tolerant to chilling injury 16 .…”

Carbohydrate metabolism in growing rice seedlings under arsenic toxicity

“…aAmylase catalyses hydrolytic cleavage of internal a-1,4-glucan bonds of starch releasing fragments that can be further broken down by b-amylase leaving a b-limit dextrin (Yang et al, 2001) while starch phosphorylase degrades starch by phosphorolytic cleavage to glucose 1-phosphate and is an enzyme used for the reversible phosphorylation of the aglucan in plant cells (Chen et al, 2002). Among the enzymes of sucrose metabolism, sucrose synthase and invertase are involved in sucrose-cleavage whereas sucrose phosphate synthase is the critical enzyme dedicated solely to sucrose biosynthesis (Guo et al, 2002). Invertases catalyse irreversible hydrolysis of sucrose to glucose and fructose (Hirose et al, 2002) whereas sucrose synthase (SS) is a cytosolic and reversible enzyme that catalyses sucrose degradation and supplies UDP-glucose and ADP-glucose for the synthesis of starch and cell wall polysaccharides (Baroja-Fernandez et al, 2003).…”