Sodium fluoride induced metabolic changes in jack pine seedlings. I. Effect on gas exchange, water content, and carbohydrates

Abstract

Dark respiration, photosynthesis, water content, and carbohydrate pools were examined in jack pine (Pinusbanksiana Lamb.) seedlings treated for 1–7 days with sodium fluoride. Compared with those of controls, both respiratory rates and respiratory quotient decreased in plants treated for 1 day. Photosynthetic rates declined in plants exposed to fluoride for 1, 2, and 4 days. Recovery was observed in seedlings treated for 7 days. A decrease in water content was noted as early as 1 day after the exposure of plants to fluoride, and seedlings treated for longer periods continued to contain less water than control plants. The following effects of sodium fluoride treatment on carbohydrates were observed. Firstly, inositol increased in plants after 1 day, glucose increased after 1 and 2 days, and starch significantly declined in plants treated for 1 day. Sucrose was also initially present in lower amounts in fluoride-treated seedlings. Plants treated for 7 days contained levels of sucrose similar to those of controls. The possibility that water stress may be partly responsible for some of the metabolic changes is discussed.