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Reproductive phenology in three Genisteae (Fabaceae) shrub species of the W Mediterranean Region

Nordic Journal of Botany (Impact Factor: 0.84). 06/1999; 19(3):345 - 354. DOI: 10.1111/j.1756-1051.1999.tb01126.x

ABSTRACT We studied the flower duration, the phenology of flowering and fruiting, and flower, fruit, and seed production in three Genisteae shrub species of the W Mediterranean Region: Cytisus multiflorus, C. striatus, and Retama sphaerocarpa. Flower duration was negatively correlated with temperature, and in the case of C. striatus it was also influenced by pollination. In Cytisus multiflorus, which flowers during winter in the population studied, two floral morphs were recognized differentiated by flower size, phenological pattern, and production of the reproductive organs: morph LF (large flowers) and morph SF (small flowers). The former is earlier in phenology but its reproductive success is less than the second since it not only produces significantly fewer flowers/plant, but also a smaller crop of fruit and seeds. The flowering of the LF morph lasted some three months and of the SF morph 11 weeks. The winter-spring flowering C. striatus, with a four month duration of flowering time, is sympatric with C. multiflorus and their flowering periods overlap, but the former is more successful reproductively. Retama sphaerocarpa is clearly spring flowering, with an extremely short duration of flowering (c. 6.5 weeks), but, unlike the other two species which disperse their seeds in the same season in which they are produced, it staggers the dispersal of its diaspores over more than one year. Despite the great flower per plant production, especially in Retama sphaerocarpa, and of the number of fruit initiated, the final crop of fruit and seed/plant is low in the three species (C. multiflorus: fruit 8.40% and seeds 1.96%; C. striatus: fruit 13.09% and seeds 4.12%; Retama sphaerocarpa: fruit 5.65% and seeds 1.33%).

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    ABSTRACT: The productivity and morphology of fruit and seeds were studied in 30 species (and subspecies) of the tribe Genisteae (Fabaceae) in south-west Spain. The morphological characters of greatest taxonomic value both for the segregation of the two subtribes (Genistinae and Lupininae) recognized in Genisteae and for the delimitation of the lower taxonomic levels (genus and species) are the size of the pod and characters of the pericarp, the colour and weight of the seeds, whether or not an aril exists, and the shape, size, and position of the hilum. In contrast, characters of little taxonomic interest are pod colour, shape and number of seeds, and characters of the lens. There were also found to be major relationships between fruit and seed, and between these and other floral (e.g. corolla size) or reproductive (e.g. pollen/ovule [P/O] and seed/ovule [S/O] ratios) attributes. Thus in this tribe, pod size was positively correlated with corolla size, seed size, the number of viable seeds/fruit, and the S/O and P/O ratios. Corolla size was positively correlated with the number of viable seeds/fruit and with the seed weight. Similarly, the number of seeds/fruit was positively correlated with the fruit's weight and with the number of ovules/ovary. Also, the weight of the seeds was positively correlated with the pollen/ovule ratio. There was also positive correlation between the S/O and P/O ratios.
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