Phosphorus Nutrition Influence on Starch and Sucrose Accumulation, and Activities of ADP-Glucose Pyrophosphorylase and Sucrose-Phosphate Synthase during the Grain Filling Period in Soybean

Abstract

Several lines of evidence indicate that the partitioning of photosynthate between starch and sucrose is influenced by the relative concentrations of inorganic phosphate (Pi) in the cytosol and chloroplast. Two greenhouse experiments were conducted to determine the influence of long-term differences in soil P levels, ranging from deficient to supraoptimum, on leaf starch and sucrose concentrations, and activities of adenosine diphosphate glucose (ADPG) pyrophosphorylase and sucrose-phosphate synthase (SPS) during the grain filling period in soybean (Glycine max [L.] Merr.). It was hypothesized that, compared with optimum P nutrition, leaf starch and sucrose concentrations would be increased and decreased, respectively, for P deficiency and visa versa for supraoptimum P nutrition. Relative to the optimum soil P level, leaf Pi concentration was not altered by P deficiency but was increased two-to fourfold for the supraoptimum soil P treatment. The concentrations of leaf starch and sucrose were not markedly affected by any of the P fertility treatments and were not closely related to the activities of ADPG pyrophosphorylase and SPS. P deficiency resulted in increased activity of both enzymes in one of the experiments. The results indicated that long-term soil P treatments, that caused either large decreases in plant growth (P deficiency) or large increases in leaf Pi concentration (supraoptimum P), did not markedly alter starch and sucrose metabolism. Furthermore, it can be inferred that the method of plant culture and/or imposition of the P treatments is a critical factor in interpreting results of P nutrition studies.The regulatory effect of Pi on the partitioning of photosynthate between sucrose and starch has been extensively studied (12,13,18,28,29,(31)(32)(33) at various times during plant development lead to enhanced starch accumulation by leaves (13,14,16,21,25). In general, treatments that alter the relative concentrations of cytosolic and chloroplastic Pi would be expected to alter starch and sucrose synthesis and accumulation. In some cases, alterations in starch and sucrose accumulation have been associated with corresponding changes in enzymes of starch and sucrose metabolism (13). It has been proposed that P deficiency during the seed filling period may decrease yield in soybean by decreasing the flow of carbon into sucrose that could be used for seed development (15).There are a few reports that indicate that P stress does not necessarily result in enhanced starch and/or decreased sucrose accumulation (8,11,29). In a previous study of vegetative development in tobacco (Nicotiana tabacum L.), it was demonstrated that leaf sucrose and starch concentrations were not markedly affected in plants grown at soil P levels ranging from severely deficient to supraoptimum (8). It was proposed that the variable effects of soil P level on starch and sucrose synthesis and accumulation may be due to experimental procedures such as the use of isolated chloroplasts versus leaves, the timing of application of P ...

Dithiothreitol decreases in vitro activity of ADP‐glucose pyrophosphorylase from leaves of apple (Malus domestica Borkh.) and many other plant species

“…The determined A 0.5 for apple leaf AGPase [0.13 mM, Fig. 1(B)] is similar in magnitude to that obtained for sugar beet (Beta vulgaris L.; 0.19 mM) leaves (Sanwal et al, 1968), lower than that of sorghum leaves (0.37 mM; Sanwal et al, 1968), but higher than those of barley leaves (5-7 µM; Sanwal et al, 1968;Kleczkowski et al, 1993), wheat leaves (0.01 mM; Grafts-Brandner, 1992), spinach leaves (45 µM) and tobacco leaves (45 µM) (Sanwal et al, 1968).…”

“…Despite the contrasting results and lack of information on other plant species, DTT has been frequently included in the routine extraction or assay mixture of AGPase from leaves of many plant species, including Arabidopsis thaliana (L.) Heyhn. (Sun et al, 1999), soybean (Grafts-Brandner, 1992), spinach (Spinach oleracea L.) (Martindale and Leegood, 1997), maize (Zea mays L.) (Causse et al, 1995), tobacco (Nicotiana tabacum L.) (Scheible et al, 1997), potato (Hattenbach et al, 1997), barley (Hordeum vulgare L.) (Kleczkowski et al, 1993) and tomato (Lycopersicon esculentum Mill.) (Sanwal et al, 1968).…”

High fertigation frequency and phosphorus level: Effects on summer-grown bell pepper growth and blossom-end rot incidence

“…Increased starch and reduced sucrose and hexose concentrations have previously been found in phosphorusdeficient plants (Craft-Brandner, 1992;Paul and Stitt, 1993;Plaxton and Carswell, 1999;Qiu and Israel, 1992), therefore the differences in the concentrations of starch in the leaves, and of sucrose and reducing sugars in the fruits, found in the present study (Figure 6), were attributed to the variations in leaf P. An indirect effect of P deficiency may be stomatal closure, since low levels of hexose-P in P-starved leaves could lead to accumulation of triose phosphate within the plastids and, consequently, to stomatal closure (Clarkson and Scattergood, 1982). The observed decreases of leaf conductance in the low-P plants ( Figure 5) are in accord with the above mechanism and with the reports of Biddinger et al (1999), and of Jacobb and Lawlor (1991).…”

Coordination of protein and mRNA abundances of stromal enzymes and mRNA abundances of the Clp protease subunits during senescence of Phaseolus vulgaris (L.) leaves

“…With few exceptions most of the information pertaining to senescence-related changes in other soluble enzymes of carbon metabolism is based on enzyme activity data. We have previously shown that phosphoribulokinase (Ru5P kinase) and Rubisco abundances decline in a coordinated manner during soybean senescence (Crafts-Brandner et al 1990) and that ADP-glucose (ADPGlc) pyrophosphorylase activity does not decline as extensively as Rubisco activity during soybean and tobacco leaf senescence (Crafts-Brandner 1992). It has also been reported that the activities of several Calvin cycle enzymes coordinately decline during senescence .…”