No contribution of the pentose phosphate pathway in dormancy‐breaking of cocklebur seeds

Abstract

The role of the oxidative pentose phosphate (PP) pathway in the dormancy‐breaking of cocklebur (Xanthium pennsylvanicum Wallr.) seeds was investigated. D‐[1‐14C]‐glucose or D‐[6‐14C]‐glucose was fed to dormant and non‐dormant lower seeds or to their axial or cotyledonary segments which were imbibed for different durations, and C6/C1 ratios of respired 14CO2 as an index of the PP pathway activity were calculated. Contrary to expectation, there was no significant difference in the C6/C1 ratios between the dormant and non‐dormant seeds or segments during a water imbition period of 24 h, although the PP pathway actually operated already in an early stage of water imbibition. Also concerning the activities of G6PDH and 6PGDH, the key enzymes of this pathway, no difference between the dormant and non‐dormant seeds was found. It was thus concluded that, unlike other seeds, there is no contribution of the PP pathway to the regulation of dormancy of the cocklebur seed.

Activities of Catalase and Pentose Phosphate Pathway Dehydrogenases during Dormancy Release in Nectarine Seed

“…If the measured enzymic activity changes do indeed reflect the in vivo situation, it is evident that the release of dormancy in nectarine seed has little to do with changes in the ppp activity. This conclusion is supported by other work (Adkins and Ross, 1981;Satoh and Esashi, 1980;Upadhyaya et al, 1981;Thévenot et al, 1989). The proposed key role of catalase in dormancy control also seems unlikely in nectarine seeds.…”

“…These data suggest that the ppp plays a positive role while catalase exhibits an inhibiting role in dormancy release. However, there are data that show that the ppp is not involved in dormancy release (Adkins and Ross, 1981;Satoh and Esashi, 1980;Upadhyaya et al, 1981). Data are conflicting on the role of the pathway in dormancy release.…”

Effects of cyanide and cold treatment on sugar catabolism in apple seeds during dormancy removal

“…1) Glucose-6-P DH (Satoh and Esashi 1980). Thirtythree mM Tris-HCl buffer (pH 7.5), 5 mM MgCU, 0.4 mM NADP (Sigma), 0.5 mM glucose-6-phosphate (Serva) and 100 ^1 enzyme extract in a final volume of 1.5 ml.…”

Changes in the synthesis of some proteins during breaking of secondarily induced thermodormancy by respiration inhibitors (cyanide, azide) and BAP in embryos ofAgrostemma githagoL. seeds

“…Roberts (1969) suggested that the dormancy-breaking process induced by respiration inhibitors is closely "Correspondence connected with an increased oxidation via the pentose phosphate pathway. There are many conflicting results regarding this suggestion (e.g., Simmonds and Simpson, 1971;Roberts and Smith, 1977;Satoh and Esashi, 1980;Gahan et al, 1986;Bogatek and Lewak, 1988;De Meillon et al, 1990). We observed no differences in the 6-14 CO 2 /l-' 4 CO 2 ratio in the metabolism of specifically labelled glucose between embryos of untreated and respiration inhibitor-treated, thermodormant Agrostemma seeds; moreover glucose-6phosphate dehydrogenase activity decreased after application of cyanide and azide (unpublished data).…”