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This study examined the effects of plant growth regulators, explant types, and their orientations on in vitro shoot proliferation of Casuarina cunninghamiana Miq. and also the subsequent rooting ability of shoots. Results showed that shoot proliferation occurred only in shoot tip explants cultured vertically on Murashige and Skoog (MS) medium supplemented with 2 or 4 µM thidiazuron (TDZ). Neither 6-benzylaminopurine alone nor in a combination with 1-naphthalene acetic acid (NAA) or gibberellic acid had any effect on shoot proliferation. TDZ at 4 µM resulted in the greatest percentage of axillary bud sprouting (70%) and mean number of sprouts per explant (2.3). Additionally, no shoot proliferation was observed from detipped or single-node explants or from horizontally placed shoot tip explants when cultured on the same TDZ-containing medium. The induced shoots produced adventitious roots on MS medium supplemented with 2.5, 5, or 10 µM indole-3-butyric acid (IBA), not with indole-3 -acetic acid and NAA. Although the mean number of roots per explant was not significantly different between 2.5 and 5 µM IBA, the highest rooting percentage (68%) and mean length of roots per explant (0.7 cm) was achieved at 5 µM IBA. The current study provided preliminary information toward commercial in vitro propagation of Casuarina cunninghamiana male plants. [ABSTRACT FROM AUTHOR]

Casuarina cunninghamiana Miq. is an introduced species to Florida that has potential as a windbreak plant to help manage canker in citrus groves; however, only Florida sources can be used for that purpose. Local sources of Casuarina are generally adequate seed producers, but germination percentages are frequently poor. Thus, the causes of low seed germination and methods to improve germination were investigated using C. cunninghamiana and a local hybrid (C. equisetifolia L. x C. glauca Sieb. ex Spreng.). Seeds of the hybrid were larger and heavier (88 mg/100 seeds) than those of C. cunninghamiana (mean wt. 67 mg/100 seeds). Shrunken, insect-damaged, and empty seeds, present in all unsorted seed lots, were responsible for poor seed germination of the four seed sources studied. Petroleum ether separation improved germination by dividing seeds into floaters and sinkers. The floater fraction consisted of 47.5% to 93% insect-damaged seeds compared with 9.0% to 43.5% among sinkers. More than 50% of the sinkers were filled seeds and less than 21% in floaters. No empty seeds were sinkers except for one source of C. cunninghamiana. In sorted hybrid seeds, petroleum ether separation eliminated a large proportion of ungerminable seeds (floaters) and seed germination among sinkers was faster with a higher germination percentage than floaters. Cumulative germination of hybrid seeds in a trial involving two temperatures was 23.0% for sunken seeds at 30 °C at the end of 8 weeks compared with 1% of unsorted seeds. Temperature had no significant effect on seed germination. The germination percentage of hybrid seeds with seedcoats removed was 91.0% in the first week of culture compared with only 1.2% in the first week and 12.6% seed germination at the end of 8 weeks' culture of intact seeds. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine whether juice quality of 'Valencia' sweet orange [C. sinensis (L.) Osb.] is affected by the type of inflorescence on which fruit are borne, and to determine the contribution of inflorescence type to within- tree variation in juice quality. During the 1998-99 and 1999-2000 seasons, fruit size and juice quality [soluble solids concentration (SSC) and titratable acidity (TA)] of fruit from `Valencia' sweet orange trees on Carrizo citrange rootstock [Poncirus trifoliate (L.) Raf. x C. sinensis (L.) Osb.] planted in 1987 at Howey-in-the-Hills, Fla., were measured. A 2x2 factorial design (inflorescence type x canopy position) with leafy and leafless inflorescence types, and southwest top and northeast bottom canopy positions was used. The type of inflorescence on which fruit were borne had a minor effect on juice quality, and inflorescence type and juice quality were not directly associated. Rather, juice SSC was associated with the effect of inflorescence type on fruit size, as small fruit tended to have higher SSC than large fruit, regardless of the type of inflorescence on which fruit were borne. The relatively small difference in SSC between fruit borne on leafy and leafless inflorescences (≈3% of mean SSC) was an indirect result of fruit size. Therefore, fruit borne on leafy inflorescences, which tend to be of larger size compared with fruit borne on leafless inflorescences, tended to have marginally lower SSC. Acid content and ratio of SSC : TA were not related to inflorescence type. In addition, the type of inflorescence on which fruit were borne made only a nominal contribution to variability in juice SSC, in contrast to the major contribution of canopy position to within-tree variation in juice SSC. Factors other than inflorescence type are important components of within-tree variation in juice SSC. [ABSTRACT FROM AUTHOR]