Carbohydrate partitioning, photosynthesis and growth in Lemna gibba G3. II. Effects of phosphorus limitation

Abstract

E, 1987. Carbohydrate partitioning, photosynthesis and growth in Lemna gibba G3. 1. Effects of nitrogen limitation -Physiol. Plant. 71: 264-270.The growth rate of Lemna gibba L. G3 was varied by limiting the supply of nitrogen (N) under otherwise constant conditions. Two experimental approaches were used. 1) A series of suboptimaiiy growing cultures were supplied daily with exponentially increasing doses of N. 2) Optimally growing cultures were transferred to a N-free medium and cuitivated in it for 10 days. Levels of starch, sucrose, glucose, fructose, and rates of COj assimilation, dark respiration and growth (RGR) were measured in both systems. At RGR ranging from optimal to 50% of optimal all measured carbohydrates accumulated. RGR below 50% of optimal caused decreased levels of soluble sugars, but increased levels of starch. Starch accumulation showed a strong negative correlation with the CO2 assimilation rate, indicating increased triose phosphate/inorganic phosphate (TP/PJ ratio in the chloroplast causing end product inhibition of photosynthesis. The data indicate that the quantitative relationship between the photosyathetic activity and the carbon utilization rate influences the activity of the sucrose synthesis pathway and thus the rate of the triose phosphate/P, exchange at the chloroplast membrane, which in turn regulates the activity of starch synthesis and the Calvin cycle.

Effects of excess nitrogen and phosphorus starvation on the extramatrical mycelium of ectomycorrhizas of Pinus sylvestris L.

“…Thorsteinsson & Tillberg 1987). In the present study the starch content increased two-fold in -P seedlings.…”

Metabolic Adaptations of Plant Respiration to Nutritional Phosphate Deprivation

“…In heterotrophic suspension-cultured C. roseus cells, rates of respiratory O2 uptake a n d C 0 2 release were always lower in cells grown in Pi-deficient versus nutrient-sufficient medium (Li and Ashihara, 1990). Similarly, the respiration rates of S. minutum and Lemna gibba declined with decreasing nutritional Pi in a manner closely correlated to a declining relative growth rate (Thorsteinsson and Tillberg, 1987;Theodorou et al, 1991). Conversely, in S. obtusiusculus, respiratory O2 consumption was stimulated at least 2-to 5-fold within the first 96 h of Pi starvation (Tillberg and Rowley, 1989), whereas in sycamore cell cultures and pea roots the rate of respiration was not affected by Pi starvation (see refs.…”

“…At the metabolic level, much attention has been devoted to the effect of Pi status on the secretion of acid phosphatases, Pi uptake rates, and other mechanisms that may serve to increase the availability of Pi to Pi-deprived cells (Goldstein et al, 1989;Lefebvre et al, 1990;Duff et al, 1991aDuff et al, , 1991b. The effects of Pi nutrition on the rates of photosynthesis and photosynthate partitioning in leaves have also been well documented (Thorsteinsson and Tillberg, 1987;Lauer et al, 1989;Fredeen et al, 1990). By contrast, investigations of the metabolic adaptations of plant respiratory pathways to Pi deficiency have been limited.…”

Effects of short‐term phosphorus deficiency on carbohydrate storage in sink and source leaves of barley (Hordeum vulgare)

“…There have been many reports on the increase in starch accumulation during P depletion in leaves that use either starch or fructans as the major storage carbohydrate (Lehnert, Vieweg & de Fekete, 1979;Foyer & Spencer, 1986;Thorsteinsson, Tillberg & Tillberg, 1987;Sicher& Kremer, 1988). The present experiment shows that in barley an increase in the accumulation of fructans rather than of starch v^^as an early response to P-starvation (Fig.…”

“…Agneta) were germinated in moist vermiculite at 27 °C for 3 or 4 d, then seedlings were transferred to slits in black Styrofoam® sheets floated on 7 1 of nutrient solution in a climate chamber under continuous light (350/^molm-'s-^), r.h. 65%, at 20 °C. Exponentially increasing nutrient concentrations were given daily to keep the plants at a relative growth rate (RGR) of 25 % (Ericsson, Larsson & Tillberg, 1982;Thorsteinsson et al, 1987). After preculture on complete medium for 2 wk, the plants were transferred to Pfree but otherwise complete media.…”