Ringkasan Perbanyakan tanaman teh [Camellia sinen­sis (L.) O. Kuntze] melalui stek tunas berdaun tunggal hanya dapat menghasilkan klon unggul dalam jumlah terbatas. Oleh sebab itu diperlukan metode alternatif dengan teknik kultur sel dan jaringan untuk perbanyakan klonal secara cepat. Dalam penelitian ini dikembangkan metode yang lebih efektif untuk regenerasi tanaman teh melalui embriogenesis somatik langsung. Massa pro­embriogenik dari eksplan kotiledon dihasilkan dengan frekuensi 56,7% dalam media MS padat setengah konsentrasi yang mengandung BAP 2 mg1L. Proliferasi, perkembangan, pendewasaan dan perkecambahan embrio somatik diperoleh dengan sistem perendaman sesaat (SPS) yang menggunakan media MS cair setengah konsen­trasi, yang diperkaya dengan zat pengatur tumbuh dengan berbagai konsentrasi. Proliferasi embrio meningkat 4,3 kali dalam media yang diberi BAP 2 mglL; perkembangan dan pendewasaannya meningkat dengan penambahan kinetin dan ABA masing-masing pada konsentrasi 0,1 mg1L yang 30% diantaranya berkecambah dan membentuk planlet tanpa penambahan zat pengatur tumbuh. Protokol SPS tersebut merupakan sistem in vitro yang berpotensi bagi proliferasi dan perkembang­an embrio somatik tanaman teh yang cepat dan sinkron dari kultur kotiledon, serta regenerasinya menjadi planlet tanpa melalui fase kalus.Summary Tea propagation by single-leaf bud cuttings has limited applications for rapid dissemination of planting materials from new elite clones. An alternative method for rapid cloning by cell and tissue culture technique is necessary. In this study we have established an improved method for tea [Camellia sinensis (L.) O. Kuntze] plant regenera­tion via direct somatic embryogenesis. Clumps of proembryogenic masses were initiated at a fre­quency of 56.7% from cotyledonary slices cul­tured on a half-strength MS agar-gelled medium supplemented with 2 mg/L BAP. Proliferation, development, maturation and germination of so­matic embryos were achieved using the temporary immersion system (TIS) provided with half­strength MS liquid media supplemented with varying concentrations of growth regulators. Em­bryo proliferation increased by 4.3-fold in me­dium provided with 2 mg/L BAP; their develop­ment and maturation were enhanced by the presence of both kinetin and ABA at 0.1 mg/L each. Germination and plant recovery were achieved at a frequency of about 30% without the use of growth regulators. The TIS protocol des­cribed above represents an in vitro system poten­tial for rapid proliferation and synchronized development of tea somatic embryos from cotyledon cultures, and their regeneration into plantlets without an intervening callus phase.

Multiple shoot formation was induced on different media from excised hypocotyl and the nodal cuttings from 5 year old trees of atemoya (Annona cherimola Mill × A. squamosa L.) cv. African Pride. The highest number of shoots were obtained from the distal part (section near the root) of the hypocotyl cultured at a photosynthetic photon flux (PPF) of 36 μmol m-2 s-1 on Murashige and Skoog basal medium (MS) supplemented with 2% sucrose, 2 mg L-1 6-benzylaminopurine (BAP), 0.5 mg L-1 6-furfurylaminopurine (kinetin), 0.1 mg L-1 biotin, 0.1 mg L-1 calcium pantothenate and solidified with 0.8% agar. The number of shoots of mature nodal cuttings cultured on modified MS medium, supplemented with 1 g L-1 ammonium nitrate and the above mentioned growth regulators and addenda, was higher than MS basal or Woody Plant Medium. Increasing the kinetin level increased the number of shoots and fresh weight. Increasing the BAP level above 2 mg L-1 decreased the number of buds, length of shoots and fresh weight. The shoots were incubated in liquid MS medium containing 50 mg L-1 indole-3-butyric acid (IBA) in the dark and after 3 days were transferred to MS basal medium in the light, supplemented with 0.25% activated charcoal and solidified with 0.8% agar. Forty per cent of the shoots rooted. The rooted plantlets were successfully transferred to soil and planted in the glasshouse and 70 per cent of them showed rapid growth. Root induction was improved by pretreatment of shoots in liquid MS containing IBA. The effects of adding cytokinins, biotin and calcium pantothenate to the hypocotyl sections at different PPF and the effect of ammonium nitrate on multiple shoot production by nodal segments of in vivo grown plants are reported.

A technique for the clonal micropropagation of carambola is described. Multiple adventitious shoots were produced on root explants placed on woody plant medium or Murashige and Skoog medium supplemented with 2.0 mg l-1 6-benzylaminopurine and 0.2 mg l-1 naphthalene acetic acid. When these shoots were excised from the roots and placed on the same medium, a multiplication rate of 2.1 per month was achieved. Shoots left on the multiplication medium for more than 7 weeks became chlorotic and eventually died. Chlorosis was avoided if the shoots were transferred to a hormone-free basal medium for a 10 day period. Shoots were successfully rooted on a basal medium containing 1% activated charcoal and were successfully transferred to soil and planted in the glasshouse.The technique provides a commercially practical technique for the clonal propagation of carambola.

Alternative breeding strategies, based on colchicine-induced autotetraploids, have been proposed as a means of introducing disease resistance into banana breeding programs. This paper describes techniques for the in vitro induction of banana autotetraploids by the use of colchicine on cultured explants. The technique can be readily applied and large numbers of autotetraploids produced. The optimum treatment involved immersing shoot tips in a 0-5% w/v colchicine solution for 2 h under aseptic conditions. Dimethyl sulfoxide (DMSO) was applied with the colchicine treatments to increase cell permeability and so absorption of colchicine, resulting in the optimum treatment unchanged at 0-5% colchicine, but including the addition of 2% v/v DMSO. Of the shoot tips treated over 30% were induced to the autotetraploid level.Methods for in vitro selection of induced tetraploids from treated diploid plantlets were also developed. Tetraploid plants were more robust with thicker pseudostems, roots and broader leaves than diploids and they could be selected on these morphological characteristics. Mean stomatal lengths of diploid banana plants growing in vitro were significantly smaller (16-0 mum) than the tetraploids (26.9 mum) and were used as a more reliable indicator of ploidy than morphological criteria alone. A root tip squash technique using carbol fuchsin was developed for positive confirmation of ploidy change by chromosome counts- Although chimerism and reversion to the diploid form occurred, it was not considered a problem because of the large number of autotetraploids induced. Stable autotetraploids were recovered and established in the field and were characterised by their large, drooping leaves and thick pseudostems. They have retained these characteristics for more than 3 years in the field.

Explants of cucumber seedlings having different lengths of hypocotyl attached were grown axenically on Murashige and Skoog medium supplemented with kinetin (2 mg L-1). Multiple shoots developed from the apical regions of all explants. In this tissue shoots may also develop at the base of the hypocotyl, but this response is strongly dependent upon the length of the hypocotyl. As the length of the hypocotyl increased beyond 5 mm, there was a rapid reduction in basal shoot numbers and a concomitant increase in root production. We suggest that these responses are related not to the ratio or concentration of endogenous growth regulators but to different regions of sensitivity to growth regulators along the hypocotyl.

Immature embryos of different sizes and ages from commercial varieties of lychee (Litchi chinensis Sonn.) were cultured in a range of different media. Embryos as small as 3 mm could be cultured using in vitro techniques and subsequently grown into plants. MS solid medium with 2% sucrose supplemented with 150 ml l -1 coconut water was most effective in stimulating the germination of immature lychee embryos. Embryos of lychee were treated to induce adventitious buds from embryonic shoots as a means of achieving multiplication

Cucumber explants including at least part of the cotyledon, a short section of hypocotyl, and the apical bud, are capable of producing multiple axillary buds from the seedling apex and adventitious shoots from the hypocotyl base in a medium which contains 2.0 mg dm-3 of kinetin. Removal of the apical bud triples the number of shoots produced from the apex of explants with two intact cotyledons but does not affect shoot production from explants with some or all of their cotyledons removed. The area of intact cotyledon also influences morphogenesis, as explants with both cotyledons removed, failed to produce adventitious shoots from the hypocotyl base. Culture in continuous darkness entirely prevents shoot development from the explant base, but has little influence on shoot production from the apex. The influence of endogenous growth regulators and apical dominance on the morphogenesis of shoots in cucumber seedling are discussed.

Protoplasts isolated from cotyledons of aseptically germinated cucumber seedlings were divided into three size classes. The relationships between tissue age, isolation procedure, yield and protoplast size were investigated. During germination and up to an age of 13 days, the percentage of protoplasts in each size class underwent considerable change with a big reduction in percentage of the largest protoplasts in older cotyledons. Protoplast size and yield could also be manipulated by varying the isolation technique. In this context, temperature, incubation time and shaker speed were significant. By selecting tissue of appropriate age and using a carefully selected isolation procedure the percentage of viable cucumber protoplasts with the ability to form a cell wall and divide can be increased considerably.

A technique for propagating Passiflora edulis plantlets from juvenile seedlings by tissue culture is described