Studies on cambial activity: advances and challenges in the knowledge of growth dynamics of Brazilian woody species

The lack of specific research on the sequence of events that determine plant growth from meristem until wood formation represents a gap in the knowledge of growth dynamics in woody species. In this work, we surveyed published studies concerning cambial activity of Brazilian native species aiming at allowing the comparison of applied methods and obtained results. The annual cambial seasonality was observed in all the investigated species. Nevertheless, we found high heterogeneity in the used methodologies. As a result from this analysis, our opinion points to the need for standardizing sampling protocols and for discussing the suitability of experimental designs. This will help to define with greater precision the factors that determine the radial growth in the different tropical ecosystems

Seasonal development of secondary xylem and phloem in Schizolobium parahyba (Vell.) Blake (Leguminosae : Caesalpinioideae)

The cambial activity and periodicity of secondary xylem and phloem formation have been less studied in tropical tree species than in temperate ones. This paper describes the relationship between seasonal cambial activity, xylem and phloem development, and phenology in Schizolobium parahyba, a fast growing semideciduous seasonal forest tree from southeastern Brazil. From 2002 to 2003, wood samples were collected periodically and phenology and climate were recorded monthly in the same period. S. parahyba forms annual growth increments in wood, delimited by narrow initial parenchyma bands. The reduction of the cambial activity to a minimum correlates to the dry season and leaf fall. The higher cambial activity correlates to the wet season and the presence of mature leaves. In phloem, a larger conductive region was observed in the wet season, when the trees were in full foliage. The secondary phloem did not exhibit any incremental zone marker; however, we found that the axial parenchyma tends to form irregular bands

Cambial dormancy lasts 9 months in a tropical evergreen species

Key message: Cambial dormancy in a tropical evergreen species is long lasting, and the initiation of cambial activity is related to day length. Abstract: Studies on cambial activity allow us to understand the growth dynamics of plants. In this study, we investigate cambial activity and the conducting phloem in a population of an evergreen shrubby species from a semi-deciduous tropical forest with distinct wet and dry seasons. Stem samples from Cordiera concolor were collected bimonthly in 2010 and prepared according to the standard methods for plant anatomy. The relationship between cambial activity and climate factors as well as phenology was investigated using Spearman’s correlation. The cambium is dormant during the rainy season and dormancy lasted up to 9 months. Cambial activity was positively related to day length, and although it occurred in the rainy season, the period of its onset and termination was not concurrent with the beginning and end of the rainy season. The conducting phloem corresponded most to the non-collapsed phloem and was present year-round, ranging in width (in transverse section) from 62 µm in the rainy season to 112 µm in the dry season. Together, these results illustrate that cambial activity in an evergreen species of a seasonal tropical forest is seasonal with long-lasting cambial dormancy, and that at least some conducting phloem is present year-round