Protein Synthesis in Dormant and Non‐Dormant Cocklebur Seed Segments

Abstract

Using the axial and cotyledonary segments of lower cocklebur (Xanthium pensylvanicum Wallr.) seeds, protein synthesis as shown by incorporation of radioactive leucine was examined in relation to their dormant status. During the first 9 h of water imbibition, the protein synthesis was higher in the dormant axes than in the non‐dormant, after‐ ripened ones. When imbibed for more than 12 h non‐dormant axes had a higher activity than dormant ones. This was also the case with the cotyledonary segments. Cyctoheximide, an inhibitor of protein synthesis, blocked protein synthesis in the axial tissue regardless of its dormant status, and thereby inhibited germination of the non‐dormant seeds. In the dormant seeds, however, cycloheximide at 3 mM slightly stimulated germination without stimulating the C2H4 production. Based on these results, it is suggested that in cocklebur seeds there may be some proteinaceous system which is involved in the maintenance of dormancy.

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

“…former to exogenously applied glucose as compared to that in the latter. Further, the higher production of '•'CO2 in dormant seeds during early imbibition coincides with the higher metabolic activity as indicated by the protein synthesis activity (Satoh and Esashi 1979). Regardless of the duration of imbibition, CJC^ ratios gave far lower values than 1, suggesting the active operation of the PP pathway during the early germination process of cocklebur seeds.…”

“…It has been proposed that the release of seed dormancy is associated with an increased activity of the PP pathway (Roberts 1973, Simmonds and Simpson 1972, Hendricks and Taylorson 1975. However, some data which we have obatined questioned the application of this view in the case of cocklebur seed dormancy , 1979a, Satoh and Esashi 1979. The low Ce/C, ratios of Tables 1 and 2 clearly indicate the actual operation of the PP pathway in imbibed cocklebur seeds.…”

“…Moreover anaerobiosis during an earlier water imbibition period, which has been considered to be unfavourable for the operation of the PP pathway, does not prevent the proceeding of germination in the cocklebur seed , and can potentiate the imbibed seeds to germinate (Esashi et al 1976a,b). Furthermore, no suppression of protein synthesis in dormant seed segments for which the actively operating PP pathway seems to be required, could be found during early imbibition (Satoh and Esashi 1979). These findings lead us to the question of whether or not the PP pathway actually functions in the regulation of dormancy of cocklebur seed.…”

Proteomic approach to analyze dormancy breaking of tree seeds

“…The transition from seed dormancy to germination is a multi-step process. Seed dormancy may be controlled by blocking or unblocking of the synthesis or activity of particular proteins involved in specific processes (Satoh and Esashi 1979). Using a proteomic approach it is now possible to investigate protein expression and modification during seed dormancy T. A.…”

F‐695 emission from the purified photosystem II chlorophyll a‐protein complex

“…PSI1 chl a, PSI1 chlorophyll u-protein complex; PSI chl a, PSI chlorophyll a-protein complex chlorophyll a-protein complex, however, indicates that there is a weak shoulder around 690-695 nm; thus the half-band width (15-17 nm) of the emission (F-685) of this complex is much larger than that of the F-68 1 band (10 nm) of light-harvesting chlorophyll a/b-protein (see also [ 191). The temperature profile of this 695 nm shoulder was very different from that of the main band (F-685); it showed a much higher temperature coefficient than that of the F-685 band over 150-77 K, suggesting that there are 54 some contributions of a component similar to that involved in the F-695 emission of chloroplasts.…”