Effect of fluoride on nucleotides and ribonucleic Acid in germinating corn seedling roots

Fluoride-Induced Inhibition of Starch Biosynthesis in Developing Potato, Solanum tuberosum L., Tubers Is Associated with Pyrophosphate Accumulation

Pretreatment of discs excised from developing tubers of potato (Solanum tuberosum L.) with 10 millimolar sodium fluoride induced a transient increase in 3-phosphoglycerate content. This was followed by increases in triose-phosphate, fructose 1,6-bisphosphate and hexose-phosphate (glucose 6-phosphate + fructose 6-phosphate + glucose 1-phosphate). The effect of fluoride is attributed to an inhibition of glycolysis and a stimulation of triose-phosphate recycling (the latter confirmed by the pattern of (13)C-labeling [NMR] in sucrose when tissue was supplied with [2-(13)C]glucose). Fluoride inhibited the incorporation of [U-(14)C] glucose, [U-(14)C]sucrose, [U-(14)C]glucose 1-phosphate, and [U-(14)C] glycerol into starch. The incorporation of [U-(14)C]ADPglucose was unaffected. Inhibition of starch biosynthesis was accompanied by an almost proportional increase in the incorporation of (14)C into sucrose. The inhibition of starch synthesis was accompanied by a 10-fold increase in tissue pyrophosphate (PPi) content. Although the subcellular localization of PPi was not determined, a hypothesis is presented that argues that the PPi accumulates in the amyloplast due to inhibition of alkaline inorganic pyrophosphatase by fluoride ions.

Effect of fluoride on in vivo nitrate reduction in the rive leaves (Oryza sativa L.)

Fluoride had no effect on in vitro nitrate reductase activity in rice leaves, but in vivo activity was strongly inhibited. It is suggested that fluoride brings about this inhibition by adversely affecting the physiological NADH generating system required for in vivo nitrate reduction.

Chilling injury and nucleotide changes in young cotton plants

The effects of chilling at 3 to 5 C on the nucleotide composition of roots and leaves of cotton (Gossypium hirsutum L.) seedlings were determined. Chilling decreased the concentration of nucleotides, especially di- and triphosphates, in both leaves and roots. Chilling also caused an increase in free nucleosides. The results are interpreted to mean that general phosphorolytic activity is associated with chilling injury rather than damage to the phosphorylating mechanisms alone. Hardening at 10 to 20 C prior to chilling protected the seedlings against subsequent chilling injury and prevented nucleotide losses.