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A highly embryogenic culture ofEucalyptus citriodora was obtained by repetitive embryogenesis from somatic embryos cultured in the dark on a medium containing 500 mg/l each of glutamine and casein hydrolysate, 30 g/l of sucrose and 5 mg/l of 1-napthaleneacetic acid. Cultures retained morphogenetic ability for upto 36 months when maintained at 27°C by subculture at intervals of 4-5 weeks. The subculture period could be extended beyond 9 months if cultures were incubated at 10°C. On a hormone free medium incubated in light 50% of the embryos germinated to plantlets of which 70% survived when transferred to a sand and soil mixture.

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Production of microspore-derived embryos from cultured anthers is now a well established technique for the isolation of homozygous lines in many crop plants. We describe here a culture method for embryo induction and plant regeneration from anthers of four sunflower genotypes. For preliminary experiments, anthers of uninucleate microspores were cultured on four types of basal media viz., Murashige and Skoog's MS, Gamborg's B5, Nitsch and Nitsch, and White's W, supplemented with 1.0 mg/l 2,4 dichlorophenoxy acetic acid and 0.5 mg/l 6-benzylaminopurine and 40 g/l sucrose. MS basal medium, being more responsive for embryo induction, was used for further experimentation. To optimise the culture requirement MS basal medium was supplemented with 0.2-2.0 mg/l 2,4 dichlorophenoxy acetic acid and 0.5 and 1.0 mg/l 6-benzylaminopurine. The effect of cold pretreatment, hormone regime and sucrose concentration were tested for embryogenic efficiency. Genotype had a significant effect on the capacity of embryo induction. Addition of silver nitrate (2.5 mg/l), an ethylene inhibitor, stimulated embryo germination. Plantlets were obtained (10-15%) from embryos of only one genotype.

Adventitious shoots were formed through callus on leaf explants of Eucalyptus camaldulensis Dehnh. (River red gum) taken from shoot cultures of mature trees. Callus formed in dark on a medium containing 1 g/l casein hydrolysate, 3 mg/l 1-naphthaleneacetic acid, 0.1 mg/l 6-benzyladenine and 50 g/l sucrose. Shoot initiation occurred in 4 weeks on calli shifted to light on a regeneration medium containing 10% coconut milk, 0.5 mg/l 6-benzyladenine and 20 g/l sucrose. Rooting occured in dark on a liquid medium containing 4 mg/l 1-naphthaleneacetic acid. Zygotic embryos of Eucalyptus citriodora Hook f. (Lemon scented gum) cultured in dark on a medium containing 3 mg/l 1-naphthaleneacetic acid and 50 g/l sucrose formed somatic embryoids which grew to normal plantlets on the same regeneration medium used for organogenesis.

Floral biology and breeding behavior were studied in the bamboo Dendrocalamus strictus Nees. The inflorescence in this species is a large branching panicle. Fertile florets are intermixed with smaller sterile ones. There are six stamens. The ovary is stipitate and turbinate. The style is long and the stigma is bifid and plumose. Dendrocalamus strictus is typically dichogamous and protogynous. The gynoecium matures 3-4 days before the androecium, effectively preventing self pollination. Flower bloom, which took place over a period of 2 to 3 h, was dependent on air temperature and only occurred between 0600 and 1300 h. Dendrocalamus strictus is anemophilous. Flowers in the male phase were visited by insects. These insects completely neglected the flowers at the female phase. The insects fed on the pollen and were not pollen vectors. When wind was excluded by enclosing the inflorescences in bags there was no seed set, indicating that cross pollination by wind is necessary for fertilization and that parthenocarpy and apomixis are not occurring in this species. Pollen fertility was about 98% as indicated by staining fresh pollen at the time of anther dehiscence and pollen release with Alexander's stain (Alexander 1969). When placed on a modified Brewbaker-Kwak medium containing 1% glucose, the pollen grains germinated well, and the pollen tubes grew to 15-20 times the diameter of mature pollen grains. Although profound protogyny has its disadvantages in times of sporadic flowering, it can be useful in breeding programs because it eliminates the need for emasculation.