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Báo cáo khoa học: "Some aspects of bud in young oak activity and branch formation"

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activity and branch formation Some aspects of bud in young oak R. Harmer GU10 4tt-I, U.K. Forest Research Station, Farnham, Surrey, Introduction Terminology Shoot extension in oak occurs by rapid This work forms part of programme to a from a preformed bud. The improve the genetic quality of oaks plant- growth distribution of leaves and buds on the ed commercially; some of this project is shoots produced in each flush is uneven. based on the vegetative propagation of In this study, axillary bud density was ca 1 selected superior genotypes. For this bud/20 mm length for most of the shoot selection programme to be successful, it but increased to ca 1 bud/2 mm at the tip: must be possible to predict future develop- the dense terminal rosette of leaves and ment of the trees. This is particularly buds of each flush is termed the ’whorl’ important when considering selection at and the remaining longer section of shoot, the juvenile, seedling or sapling stage, the ’interwhorl’ stem when (Fig. 1). readily propagated plants are more but of unknown potential. Epicormic branches, poor stem form and the unfavourable ratio of crown and trunk biomass are important characters Mineral Nutrition determining the quality of a crop. Favour- able changes in these will have a marked effect on value. They are probably interre- In spring 1986 dormant 1 yr old seedlings lated phenoma resulting from bud produc- of Q. petraea, which had flushed twice but tion, bud activity and branch growth. not branched, were decapitated below the Detailed data on these aspects of growth 1 st whorl (see Fig. 1) and planted into are few but this information is essential for 15 cm pots of peat-sand-perlite. Plants the development of procedures for early were grown in an unheated greenhouse testing. The following experiments investi- and fertilised at weekly intervals with a gated the effect of nitrogen nutrition and liquid feed containing either 1 or 10 mM bud position on the formation of branches sodium nitrate, these were low N and high in Quercus petraea seedlings. N plants, respectively. There were 40
replicates of each treatment. The number plants produced 2-3 times more than low of axillary buds and branches which form- N plants (Table I). ed within the whorl and on the interwhorl The number of buds forming branches stem of each flush was counted on as a percentage of the total number in several occasions during summer. whorls and on interwhorl stems for the 1 st High N plants were more vigorous than and 2nd flushes of growth are shown in low N plants producing longer shoots with Table II. The values were always
smaller percentages, Table II) formed Position of bud branches than interwhorl stem buds. planted in 10 cm pots of 3:11 Acorns were and placed in a heated green- peat-grit house with 18 h day length; plants were Conclusion treated at 14 day intervals with 8:4:4 NPK liquid fertiliser. After 3 flushes of growth, plants were decapitated at the sites shown potential to form branches varied be- The in Fig. 1. There were 15-20 replicates for tween buds and different parts of the each treatment. The number of branches shoot; whorl buds were more likely to pro- formed on each interwhorl stem and whorl duce branches than interwhorl stem buds. were counted after reflushing had oc- Most buds remained inactive but the num- curred. ber which developed into branches was influenced by mineral nutrition of the plant; acrotonic and branch- Growth new was a high nitrogen regime was associated only produced on the whorl or es were with more branch production. If decapita- interwhorl stem immediately below the tion tests can be used for the early selec- decapitation cut. The percentage number tion of oak (Leakey, 1986), it will be impor- of buds active in plants decapitated above tant to control mineral nutrition: more whorl was greater than those decapitat- a difficult is the requirement to define criteria ed below a whorl (Fig. 1j. Although there for the location of decapitation cuts. were more buds on interwhorl stems, most branches were formed in whorls (Fig. 1). Field observations showed a similar result: whorls produced 3 times as many References branches as interwhorl stems and applica- tion of NPK fertiliser doubled the number of branches produced. R.R.B. (1986) Prediction of branching Leakey habit in clonal Triplochiton scleroxylon. ln: Crop These results are reflected in the intact Physiology of Forest Trees (Tigerstedt P.M.A., plants from the nutrition experiment where Puttonen P. & Koski V., eds.), University of proportionately more whorl buds (i.e., Helsinki, Finland, pp. 71-80

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