Original paperDuration of cambial activity is determined by water availability while cambial stimulus is day-length dependent in a Neotropical evergreen species

- The beginning of cambial activity can be predicted by increasing day length.
- Soil water supply manipulation do not affect the beginning of cambial activity.
- Cambial dormancy can be sooner or later in accordance with the soil water supply.
- Soil water supply breaks the link between dormancy and day length variation.
- Soil water supply affects cambial activity duration but not its initial stimulus.

Experimental manipulations are essential for understanding the causal factors of plant growth and cambial activity. Here, we studied the potential effect of water availability and natural variation of day length and temperature on cambial activity in Cordiera concolor (Cham.) Kuntze, an evergreen tropical species. Experiments were conducted in a greenhouse using ninety one-year-old plants divided into two groups. Each group was observed for five weeks during two different times of the year (early spring and late summer). Plants were subjected to three distinct water regimes (waterlogging, field capacity and water deficit). Temperature and day length were recorded daily and stem samples were taken weekly during both sampling intervals. Anatomical procedures were used to describe the cambial activity per stem. Our results suggest that soil water content and its influence on cambial activity depend on the time of year, while cambial stimulus was positively related to day length, independent of the time of year. In early spring, cambial activity was stimulated by an increase of day length, regardless of water supply. In contrast, in late summer, cambial dormancy was delayed in waterlogged plants and advanced in plants subjected to a water deficit, followed by decreasing day length. Analyses of the wood anatomy showed that the marginal bands of axial parenchyma were initial. Our study highlights a more complex scenario of plant functioning and its causal factors in tropical systems.