Photoacoustic detection of C2H4 emission from germinating striga seeds

Abstract

Parasitic weeds of the genus Striga (Scrophulariaceae) cause severe damage to graminaceous and leguminous crops in tropical and semi tropical areas. The food crop yield is directly affected i n these regions due to heavy infestations by these parasites [I]. The root-parasitic and flowering plant,s germinate in the neighborhood of the roots of the host plant, only in the presence of a germination stimulant which is produced by the roots. Therefore, their life cycle is closely coupled to t,he life cycle of the host plant, which ensures that a suitable host plant is available for further development of the parasite. The determination of the natural germination stimulants and their chemical analogues is of interest as it can be used for controlling the unbridled germination of these plants. Natural germination stimulants found so far are not suitable for controlling the germination of Striga; they are either too unstable (dihydrosorgoleone, fig 1) or the preparation is too difficult to produce them in large quantities (strigol) [2]. The synthetic analogue GR24 of strigol can be produced in sufficient quantities [3]. I t is hypothesized that GR24 owes its effect to eliciting the biosynthesis of ethene [4]. In this contribution we study the germination of Striga under addition of GR24 and ACC (1aminocyclopropane-1-carboxylic acid, the precursor of ethene in biological processes). In previous gaschromatographic studies the time development of the ethene production could not be observed due to the low sensitivity (5-10 ppb) of the gaschromatograph for ethene.