Co-Authors:
Plakhine, D., Department of Plant Pathology and Weed Research, ARO, Newe-Yáar Research Centre, PO Box 1021, Ramat-Yishay 30095, Israel
Ziadna, H., Department of Plant Pathology and Weed Research, ARO, Newe-Yáar Research Centre, PO Box 1021, Ramat-Yishay 30095, Israel
Joel, D.M., Department of Plant Pathology and Weed Research, ARO, Newe-Yáar Research Centre, PO Box 1021, Ramat-Yishay 30095, Israel
Abstract:
BACKGROUND: Parasitic Orobanchaceae germinate only after receiving a chemical stimulus from roots of potential host plants. A preparatory phase of several days that follows seed imbibition, termed conditioning, is known to be required; thereafter the seeds can respond to germination stimulants. The aim of this study was to examine whether conditioning is essential for stimulant receptivity. RESULTS: Non-conditioned seeds of both Orobanche cumana Wallr. and O. aegyptiaca Pers. [syn. Phelipanche aegyptiaca (Pers.) Pomel] were able to germinate in response to chemical stimulation by GR24 even without prior conditioning. Stimulated seeds reached maximal germination rates about 2 weeks after the onset of imbibition, no matter whether the seeds had or had not been conditioned before stimulation. Whereas the lag time between stimulation and germination response of non-conditioned seeds was longer than for conditioned seeds, the total time between imbibition and germination was shorter for the non-conditioned seeds. Unlike the above two species, O. crenata Forsk. was found to require conditioning prior to stimulation. CONCLUSIONS: Seeds of O. cumana and O. aegyptiaca are already receptive before conditioning. Thus, conditioning is not involved in stimulant receptivity. A hypothesis is put forward, suggesting that conditioning includes (a) a parasite-specific early phase that allows the imbibed seeds to overcome the stress caused by failing to receive an immediate germination stimulus, and (b) a non-specific later phase that is identical to the pregermination phase between seed imbibition and actual germination that is typical for all higher plants. © 2009 Society of Chemical Industry.