Περίληψη:
Background and AimsThe Campanulaceae is a large cosmopolitan family, but is understudied in terms of germination, and seed biology in general. Small seed mass (usually in the range 10-200 g) is a noteworthy trait of the family, and having small seeds is commonly associated with a light requirement. Thus, the purpose of this study was to investigate the effect of light on germination in 131 taxa of the Campanulaceae family, from all five continents of its distribution.MethodsFor all taxa, seed germination was tested in light (8 or 12 h photoperiod) and continuous darkness under constant and alternating temperatures. For four taxa, the effect of light on germination was examined over a wide range of temperatures on a thermogradient plate, and the possible substitution of the light requirement by gibberellic acid and nitrate was examined in ten taxa.Key ResultsFor all 131 taxa, seed germination was higher in light than in darkness for every temperature tested. Across species, the light requirement decreased significantly with increasing seed mass. For larger seeded species, germination in the dark reached higher levels under alternating than under constant temperatures. Gibberellic acid promoted germination in darkness whereas nitrates partially substituted for a light requirement only in species showing some dark germination.ConclusionsA light requirement for germination, observed in virtually all taxa examined, constitutes a collective characteristic of the family. It is postulated that smaller seeded taxa might germinate only on the soil surface or at shallow depths, while larger seeded species might additionally germinate when buried in the soil if cued to do so by fluctuating temperatures. © The Author 2013.
Συγγραφείς:
Koutsovoulou, K.
Daws, M.I.
Thanos, C.A.
Λέξεις-κλειδιά:
germination; growth response; light effect; nitrate; nutrient uptake; seed; seed production; soil depth; soil surface, gibberellic acid; gibberellin; nitrate; nitric acid derivative, article; Campanulaceae; constant vs. alternating temperatures; darkness; drug effect; germination; growth, development and aging; light; light requirement; physiology; plant seed; seed mass; temperature, Campanulaceae; constant vs. alternating temperatures; germination; gibberellic acid; light requirement; nitrate; seed mass, Campanulaceae; Darkness; Germination; Gibberellins; Light; Nitrates; Seeds; Temperature
