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  • Author or Editor: Kenneth W. Leonhardt x
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Most invasive species are prolific seed-producing landscape ornamental plants that have been introduced to non-native habitats with limited or no natural controls on their reproduction and spread. Techniques for converting prolific seed-producing landscape ornamentals into sterile or nearly sterile forms are available. Oryzalin and colchicine have been used to double chromosomes, resulting in autotetraploids with reduced fertility and potential parent plants of sterile triploids. Guard cell measurements and flow cytometry have been used to determine ploidy conversion and identify polyploids. Complete sterility has been achieved in three species of shower trees (Cassia sp.), and up to a 95% reduction in seed production has been achieved in royal poinciana (Delonix regia) and african tulip tree (Spathodea campanulata). Monkey pod (Albizia saman) crosses have produced triploid progeny to evaluate for sterility.

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Novelty Araliaceae potted plants were created by a wide variety of interspecific and intergeneric graft combinations. Twenty-four species of 10 genera were tested, of which 20 species of eight genera resulted in 85 graft combinations that grew. Intergeneric graft combinations with Schefflera arboricola included eight species in five other genera. Intergeneric graft combinations with x Fatshedera lizei included 11 species in five other genera. Schefflera arboricola scions grew more vigorously on Nothopanax and Polyscias rootstocks than on Schefflera root-stocks. The highest intergeneric graft compatibility scores for each genera included combinations with Schefflera. Plant propagation instructors may find these results useful in designing grafting exercises.

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Dehydration effects on freezing characteristics and survival in liquid nitrogen were studied in 11 species of tropical seeds and in silver maple (Acer saccharinum L.) seeds. Differential thermal analysis was used to determine the threshold moisture level below which seed tissue water was in an unfreezable state. Desiccation-sensitive seeds, areca palm [Chrysalidocarpus lutescens (Bory) Wendl.] and silver maple, did not survive dehydration below the threshold moisture level and did not survive exposure to liquid nitrogen. Nine of 10 desiccation-tolerant seeds [strawberry guava, Psidium cattleianum Sabine; passion fruit, Passiflora edulis f. flavicarpa Deg.; Ceara rubber, Manihot glaziovii Mull. Arg.; dwarf schefflera, Schefflera arboricola (Hayata) Merrill; common guava, Psidium guajava L.; papaya, Carica papaya L., apple of sodom, Solarium sodomeum L.; prickly poppy, Argemone glauca Pope; and seamberry, Sabalparviflora Becc.] survived dehydration to as low as 2% to 12% moisture content (below the threshold moisture levels determined) and in the dehydrated state survived exposure to liquid nitrogen. Coffee (Coffea arabica L. var. Bourbon) seeds tolerated dehydration to as low as 8% moisture content but did not survive exposure to liquid nitrogen. These results demonstrate the feasibility of cryopreserving seed germplasm of several tropical species.

Open Access