Influence of nitrogen on germination and early development of broomrape (Orobanche spp.)

• Published in: Weed science Vol. 47; no. 1; pp. 2 - 7
• Main Authors: Westwood, J.H, Foy, C.L
• Format: Journal Article
• Language: English
• Published: 01.01.1999
• Subjects: ammonium chloride; ammonium nitrate; ammonium sulfate; application rate; growth; inhibition; nitrogen; nutrient availability; nutrient sources; Orobanche aegyptiaca; Orobanche cernua; Orobanche crenata; orobanche minor; Orobanche ramosa; phytotoxicity; plant development; potassium nitrate; radicles; roots; seed germination; seedlings; species differences
• ISSN: 0043-1745; 1550-2759
• DOI: 10.1017/S0043174500090573

Broomrapes are parasitic angiosperms that live on the roots of many important crop plants. We have conducted a series of in vitro experiments to investigate the direct effects of nitrogen fertilizers on broomrape seed germination and early development. These experiments confirm that nitrogen in the ammonium form is more inhibitory than nitrate, but we conclude that it is the elongation of the seedling radicle that is primarily inhibited by ammonium, rather than the seed germination itself. Reductions in radicle length were observed when ammonium solutions were applied during either preconditioning or germination periods. For germinating seeds, exposures to ammonium sulfate of 4 to 8 h (depending on the species) reduced radicle elongation by half, indicating a relatively rapid inhibition. Broomrape species varied in sensitivity to ammonium, with Orobanche aegyptiaca being the most tolerant, Followed by O. crenata, O. ramosa, O. cernua, and finally O. minor as compared in the presence of 5 mM ammonium. However, all broomrape species were much more sensitive to ammonium toxicity than were host crop species under similar treatment conditions.