Abstract
ABSTRACT Growth rings have been reported for several tropical species under seasonal precipitation regimes and have often been related to leaf phenology. We investigated growth ring distinctiveness, wood markers, and leaf shedding and flushing patterns of 16 tree species from a subtropical seasonal deciduous forest under abundant and well-distributed rainfall regime in southern Brazil. Distinct growth rings were found in 13 species, 10 of which presented clear anatomical boundaries. Seven species were deciduous, five semideciduous and four perennial. Leaf shedding peaked during winter and spring months for the deciduous species, while it peaked during spring and summer months for the perennial and semideciduous species. Leaf flushing peaked in spring and summer for all species. All the deciduous species exhibited growth rings with clear boundaries. Marginal parenchyma, associated or not with other anatomical markers, was present in deciduous species but was not present in species with other leaf shedding patterns. Growth rings in Allophylus edulis, Erythrina falcata, Jacaranda micrantha and Luehea divaricata were described for the first time. The presence of seasonal leaf phenological patterns and growth rings in most of the species suggests that seasonality of the photoperiod and/or temperature influence the development of trees in moist subtropical seasonal deciduous forests.
Highlights
Growth rhythms in woody plants usually affect the morphology of their secondary tissues, forming radial anatomical patterns in the xylem, phloem and/or rhytidome known as growth layers or growth rings (Fahn et al 1981; IAWA Committee 1964; Silva et al 2019)
The identification of growth rings in taxa from tropical and subtropical regions has been hindered due to conceptual divergences from what is observed in highlatitude floras, which neither incorporate the great diversity of wood anatomy types seen in tropical floras nor their ecological and evolutionary drivers
This study confirmed the hypothesis that most tree species sampled from the subtropical seasonal deciduous forest have distinct growth rings, as found in tropical seasonal deciduous forests
Summary
Growth rhythms in woody plants usually affect the morphology of their secondary tissues, forming radial anatomical patterns in the xylem, phloem and/or rhytidome known as growth layers or growth rings (Fahn et al 1981; IAWA Committee 1964; Silva et al 2019). Tropical taxa that reach subtropical belts find a contrasting climate environment, with more intense cold and frequent mild frosts in winter (Corlett 2013). In this zone, cambial activity is likely influenced by photoperiod and/or temperature, so that cell division and growth is stimulated by the longer and warmer days of summer (Jacoby 1989; Oliveira et al 2009; Spathelf et al 2010; Shimamoto et al 2015; Kanieski et al 2017; Reis-Ávila & Oliveira 2017). Other combinations of formation rhythms and distinctness have been reported for growth rings in tropical and subtropical plants (e.g., Jacoby 1989; Borchert 1999; Alves & Angyalossy-Alfonso 2000; Callado et al 2001a; Tarelkin et al 2016; Baker et al 2017)
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