By differential screening of a cDNA library constructed from poly (A+) RNA of ABA-treated seeds of Fagus sylvatica L., we have isolated an ABA-responsive clone that is present in dormant seeds and under conditions that maintain dormancy, but it tends to disappear under conditions breaking seed dormancy. A search of the sequence data bases showed that the clone codes for a Glycine-Rich Protein and has sequence similarity to RNA-binding proteins. The clone, which exibits the characteristics of lea-genes, is up-regulated by ABA and down-regulated by GA3. Paclobutrazol abolishes the effect of GA3, which is restored upon addition of GA3. The possible relationship of this Glycine-Rich Protein to seed dormancy in F. sylvatica is discussed.

No abstract

Cuttings were either decapitated or both decapitated and disbudded at different time intervals. Cytokinin, at different concentrations, was applied to the cuttings in lanoline. Higher concentrations of cytokinin inhibited root initiation during the early stage. However, the inhibitory effect of cytokinin disappeared during the later stage of root initiation. Lower concentrations of cytokinin promoted the root initiation during the early stage. This effect was observed on cuttings which were only decapitated. These results seem to indicate that the influence of cytokinin changes with the stage of development. There seems to be an interaction between cytokinin and one or more other growth factors. A possible reason for this may be that cytokinin, in higher concentrations, produces inhibitory effects during the early part of root initiation by blocking the activity of auxin. The loss of the inhibitory effect of cytokinin during the later part of the initiation phase suggests that, at this stage, developing root primordia are capable of controlling the level of active cytokinin and thus do not react to the exogenous application of cytokinin.

Pea plants were grown at different irradiances for eleven days. At this stage they were used for cuttings. The irradiance during the rooting period (155 mW · dm−2) was the same in all the experiments, Cuttings from stock plants cultivated at the weakest irradiance obtained the highest number of roots, and the poorest rooting appeared in cuttings from stock plants grown at the highest irradiance. The results indicate that the nutritional status of the stock plant is an important factor for root formation in the cutting. Light may influence the production of inhibitors which directly or indirectly affect root formation. The possible role of carbohydrates and growth promoters in the process of root formation is discussed.

Dormancy and desiccation tolerance were studied inFagus sylvaticaseeds subsequent to 0–26 weeks of either moist prechilling (5°C) or warm (15°C) pretreatment at a restricted water content of 34% (fresh weight basis), i.e.c. 5% below full imbibition. After the pretreatments, seeds were either fully imbibed at 5 or 15°C, or dried for 7 d to around 13% moisture content and then fully imbibed at 5°C. Most of the dormancy was released after 5 weeks of prechilling, with nearly 70% of the seeds germinating at 15°C, and dormancy was fully released after 11 weeks of prechilling. Most of the seed desiccation tolerance, measured as the final germination percentage for dried seeds, was lost between 11 and 13 weeks of prechilling. A further decline in desiccation tolerance was recorded from 13 to 19 weeks, with a moderate recovery after 26 weeks. Germination was compared with the expression of a previously described abscisic-acid-responsive GRPF1 mRNA for a glycine-rich protein inF. sylvatica. There was a clear decline in accumulation of the transcript in seeds during prechilling, but not during the warm pretreatment. The amount of GRPF1 expression correlated significantly (P< 0.001) with dormancy status.