Seed germination requirements of Viburnum lantana were investigated by experiments both in the laboratory and outdoors. Embryo length, radicle emergence and shoot emergence were analysed to determine the level of morphophysiological dormancy (MPD) of seeds. Mean embryo length in fresh seeds was 1.30 mm, and required growth to at least 2.51 mm to germinate. The critical embryo length was 4.1 mm. In the laboratory, the embryo reached 3 mm length after 20 weeks of warm-temperature incubation (20/7 or 25/108C), which in fact represents a combination of warm þ cold stratification. In seeds subjected to cold stratification (1.5 or 58C) for 24 weeks, embryos hardly grew. Gibberellic acid stimulated embryo growth and germination. In the outdoor phenology test, the embryos grew from 1.30 mm, i.e. fresh seeds sown in September, to 2.98 mm at the end of the following March. In the 'move-along' test (laboratory), starting with temperatures of warm stratification [i.e. 25/108C (4 weeks) ! 20/78C (4 weeks) ! 15/48C (4 weeks) ! 58C (12 weeks) ! 15/48C (4 weeks)], and in the outdoor phenology study on seeds exposed to a similar temperature sequence, radicle emergence percentages reached 73% after 28 and 35 weeks, respectively. V. lantana does not exhibit a delay between root and shoot emergence, dismissing any kind of epicotyl dormancy. Seeds of V. lantana have non-deep simple MPD, a level not detected previously in the genus Viburnum, with the physiological dormancy component overcome by a combination of warm and cold stratification, preferably in that order.

SUMMARYWe studied the germination ecology of Scilla paui and Scilla ramburei to check the existence of underdeveloped embryos, as well as to verify the presence of any physiological or morphophysiological dormancy levels described for the family Liliaceae. Seeds of S. paui had fully developed embryos at seed dispersal and they were physiologically dormant. After eight weeks of cold (5 ºC) stratification followed by a four-week incubation at 15/4 ºC in darkness, germination was 100 %. This record, along with the promotion of germination mediated by gibberellic acid, pointed out that seeds of S. paui had non-deep physiological dormancy. In S. ramburei seeds, the average embryo length at dispersal was 1.60 mm; they had to grow to the critical length of 2.14 mm to be able to germinate. Embryo growth and radicle emergence occurred after seed exposure to a sequence of temperatures typical of the end summer-beginning autumn period. Emerged radicles required two months of exposition to winter cold (5 ºC) for seedling emergence in February and March. Seeds of S. ramburei had deep simple epicotyl morphophysiological dormancy. The differences detected in the germination ecology support the segregation of both taxa as different species, and suggest the convenience of taking into account physiological traits in systematic studies.Key words: underdeveloped embryos, morphophysiological dormancy, physiological dormancy. RESUMENSe analizó la ecología germinativa de Scilla paui y Scilla ramburei para comprobar la posible existencia de embriones subdesarrollados, así como para verificar si poseían alguno de los tipos de latencia conocidos para Liliaceae. Las semillas de S. paui presentaron embriones perfectamente desarrollados al dispersar sus semillas y latencia fisiológica. Tras ocho semanas de estratificación fría (5 ºC) y posterior incubación durante cuatro semanas a 15/4 ºC en oscuridad, se alcanzó el 100 % de semillas germinadas. Este hecho, unido al efecto estimulador del ácido giberélico, indicó que las semillas de S. paui poseían latencia fisiológica no profunda. En S. ramburei el tamaño medio del embrión al dispersar fue 1,60 mm, y para poder germinar tuvo que crecer hasta el tamaño crítico de 2,14 mm. El crecimiento del embrión y posterior emergencia de las radículas se produjo tras la exposición de las semillas a una secuencia de temperaturas propias de finales de verano y principios de otoño. Tras la emergencia de la radícula, a finales de noviembre, se requirieron dos meses de exposición al frío invernal (5 ºC) para la emergencia de las plántulas en febrero y marzo. Las semillas de S. ramburei mostraron latencia morfofisiológica simple y profunda del epicotilo. Las diferencias en ecología germinativa apoyan el mantenimiento de ambos taxones como especies diferentes, así como la conveniencia de tener en cuenta los caracteres fisiológicos en los estudios de sistemática.Palabras clave: embriones subdesarrollados, latencia morfofisiológica, latencia fisiológica.

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Seventy-five tops of D. sanderiana were grown and harvested, 15 from each of five different shade intensities. The leaf blades of each top were separated as to position in the stem. Composite samples of the leaves having the same numbered position in the 15 tops at each level of shade were chemically analyzed for nitrogen, phosphorus, potassium, calcium, and magnesium. Leaf position definitely influenced the chemical content of the leaves. The immature leaves showed lower values of nitrogen, calcium and phosphorus. The values increased with age. There was a reduction in the chemical content farther down in the stem. Leaf potassium was high in the young leaves with a definite decrease with age, until it became stabilized or it increased in the old leaves. Leaf phosphorus did not seem to vary with age. The shade intensities did not seem to affect the leaf nutrient content markedly, except potassium and magnesium to some extent, expecially in immature leaves. Functional relationships were established for leaf position and leaf nutrient content, with a high percentage of explanation of the variability. It can be concluded that leaf samples midway in the stem are suitable for analysis. Leaves of the 2d, 3d or 4th position will possibly reflect the nutritional status of the plant.

A search has been conducted for suitable native materials for potting and rooting mixtures as substitutes for peat moss in the production of ornamental plants in Puerto Rico. Materials such as sawdust, wood shavings, muck soil, residues from the tobacco industry, spent coffee, coffee parchment, dry coffee leaves, sugarcane bagasse, and peat moss were mixed with perlite, vermiculite, calcined clay, or sand and these various mixtures were evaluated as rooting media. Asparagus sprengeri did not grow well in tobacco residue or spent coffee mixtures. Potting mixtures made with dry coffee leaves and muck soil were as good as those made with peat moss. Sugarcane bagasse, wood shavings, and sawdust were intermediate in value as potting mixtures for plant healthiness and appearance. Dracaena sanderiana tops were placed in a constant mist propagator to root in different media. Wood shavings did not prove suitable for foiled or bound plants. Sugarcane bagasse, dry coffee leaves, coffee parchment, water hyacinth roots, and sawdust resulted in very stable bound plants comparable to those rooted in peat moss. Residues from the tobacco industry caused a basal-end rot but the cuttings eventually produced roots at the nodes.