Phragmites die‐back: toxic effects of propionic, butyric and caproic acids in relation to pH

Abstract

Symptoms which are associated with die-back in Phragmites : growth inhibition, root and bud death, premature shoot senescence, blocked aeration and vascular systems, especially in rhizomes and roots, and abnormal surface and internal cell-wall lignification and suberization of roots were induced by each of three of the lower volatile organic acids, propionic, butyric and caproic. These acids were applied in nutrient media in concentrations similar to those previously associated with die-back sites and\or in sediments containing rotting rhizomes and roots of the plant. At concentrations of 1n4 and 0n56 mM, respectively, butyric and caproic acids were each found to be highly toxic at pH 4n5, but relatively innocuous at pH 6. Propionic acid, applied at a much higher concentration of 10n4 mM, was highly toxic at both pH 4n5 and 6. The results support previous findings that the undissociated forms of the organic acids are the more toxic. Rhizomes and roots, rotting in water or waterlogged sand, released cocktails of acids and produced pH in the range 4n8-5n4. Phragmites seedlings planted in these media died within 12 h. Overall, the results support the theory that die-back in Phragmites can be induced and\or perpetuated by organic acids released from the decaying underground parts of the plant or other sources of organic matter.

Flooding tolerance: suites of plant traits in variable environments

“…In addition, volatile lower organic acids (e.g. propionic and butyric acids) can accumulate in waterlogged soils and damage roots (Armstrong and Armstrong 1999). These organic acids, as well as high CO 2 , can impose 'acid loads' on cells of roots in waterlogged soils (Greenway et al 2006).…”

Phytotoxicity induced by Phragmites australis: an assessment of phenotypic and physiological parameters involved in germination process and growth of receptor plant

“…Several studies have identified chemicals within P. australis organs which have antialgal, antifungal, or antibacterial effects (Li & Hu 2005). Some chemicals produced by the decomposition of belowground organs of P. australis may be responsible for the die back of P. australis itself (Armstrong & Armstrong 1999), and photodegradation of secreted phytotoxins by P. australis executes severe phytotoxicity to other plant species ). Previous studies have shown that water extracts of P. australis organs have strong phytotoxic effects on germination and growth of other plant species (Rudrappa et al 2007; Uddin et al 2012).…”

Phytotoxicity, not nitrogen immobilization, explains plant litter inhibitory effects: evidence from solid‐state 13C NMR spectroscopy

“…Hundreds of phytotoxic organic molecules have been identified and quantified in plant litter, including short-chain organic acids (Armstrong & Armstrong, 1999), tannins (Kraus et al, 2003) and phenols (Blum et al, 1999), among many others. However, single molecules alone hardly explain the entirety of the inhibitory effect of plant litter during the decomposition process (An et al, 2001).…”