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  • Author or Editor: W. P. Hackett x
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Abstract

Although for an entire plant, vegetative and reproductive development may proceed concurrently, at each shoot apical meristem a transition occurs from leaf production to bract or sepal production at the time of flower initiation. Subsequent stages of reproductive development are equally differentiated from that of vegetative development. Hence, vegetative and reproductive development represent alternative courses of differentiation of apical meristematic tissues.

Open Access
Authors: and

Abstract

The root-regenera ting potential (RRP) of one-year-old Pistacia chinensis seedlings at different growth stages was determined by recording the number of newly initiated roots during the period of 4 weeks after bare-root transplanting into a bottom misting chamber. RRP of intact pistacias was greatest when leaves were fully expanded and the terminal bud was forming (stage III) and lowest when seedlings were in a dormant condition (stages V and VI). However, seedlings disbudded before transplanting and also root cuttings showed two peaks in RRP; one at spring bud break (stage I) and the other at stage III. Removal of buds resulted in decreased RRP at stage I, but had little effect when plants were dormant. Treatments such as thiourea sprays of growing seedlings and chilling of dormant seedlings enhanced bud break and RRP. Potassium indolebutyrate applied to the root system promoted RRP of pistacia seedlings but did not eliminate the seasonal variation of RRP. Potassium indolebutyrate could replace the influence of buds only when seedlings were not in a dormant condition. Sucrose feeding via the stem substantially increased RRP at spring bud break. The results indicate that the dormant condition of buds and the availability of carbohydrates are the factors controlling the RRP of bare root transplanted pistacias.

Open Access

Abstract

Seeds of Citrus sinensis (L.) Osbeck cv. Valencia obtained from trees grown in north-central California would not germinate when fruit was harvested during the early part of the season (November 1978). Seeds from November-harvested fruit stored at 3 to 4°C for 21 days germinated 100%. A similar germination response to low temperature was obtained when seeds from fruit harvested April 1980 (exposed to only 103 hours below 3 to 4°) were treated for 3 weeks at 3 to 4°. Treatment with gibberellic acid (GA3) induced about 55% germination in seeds from non-cold-treated fruit. Germination rates for seeds from cold-treated fruit were found to increase when the seeds were presoaked in GA3 or germinated at high temperature.

Open Access

Abstract

Rooting of stem cuttings of Bougainvillea cv. San Diego Red, Ceratonia siliqua L., Chrysanthemum morifolium Ramat. cvs. Golden Anne and Mandalay, Euonymus japonica L. cv. Yellow Edge, Euphorbia pulcherrima Willd. cv. Eckspoint C-1 Red, Hedera helix L., Trachelospermum jasminoides [Lindl.] Lem., Juglans hindsii (Jeps.) Jeps., Pistacia chinensis Bunge, and Salix laevigata Bebb. is greatly promoted by basal dipping in H2SO4 prior to applying indolebutryic acid. Pre-treatment with NaOH results in considerable increase of rooting of cuttings of Rhododendron (Pericat) cv. Sweetheart Supreme, Bougainvillea, Liquidambar styraciflua L., Osmanthus heterophyllus G. Don cv. Ilicifolius, and Pinus radiata D. Don.

Open Access

Abstract

Root regeneration from root cuttings of both difficult-to-transplant Pistacia chinensis and moderately easy-to-transplant Liquidambar styraciflua was studied in a sphagnum peat medium varying from 0-100% Ca saturation and from 0-50% air filled porosity. Maximum root regeneration of Pistacia root cuttings was obtained at 75% Ca saturation and 30% and 40% air filled porosity, whereas Liquidambar root cuttings regenerated roots best at 25% Ca saturation and at 20% to 40% air filled porosity. Indolebutyric acid applied to the root cuttings greatly increased root-regenerating potential of Pistacia root cuttings but did not affect the optimum Ca and aeration requirement(s). Similarly, indolebutyric acid treatment greatly promoted the root-regeneration potential of Liquidambar root cuttings. Satisfactory root-regenerating conditions of both Ca saturation and air filled porosity for Liquidambar root cuttings were a little broadened by indolebutyric acid (IBA) application.

Pistacia bare root seedlings also required high levels of Ca saturation and aeration for optimum root regeneration. Considerably greater numbers of roots were regenerated in peat having 75% Ca saturation and 20% air filled porosity than in peat having 0% Ca saturation and 5% air filled porosity. Root regeneration was not improved by increasing only the air filled porosity when Ca was low.

Open Access