A Study of Water Dynamics and Phenology in Plant Parts of ‘Eva’ Apple Trees Grown under Winter Conditions in Southern Brazil

Aims: The objective of this study was to evaluate water dynamics in different tissues of apple 'Eva' during dormancy stage under mild winter conditions of Pelotas, located in Southern Brazil.

Study Design: Experimental design was completely randomized, with five replications, and the experimental unit was composed by a single plant, on 3x3x4 factorial arrangement, obtained from a combination of factors: three different tissues (bud, bark, and wood), three plant positions (apical, median and basal) and four collection dates each year (during the months of August and September).

Place and Duration of Study: This research was carried out during two consecutive growing seasons: 2015/2016 and 2016/2017, in an experimental apple orchard located at Palma Agriculture Center, Federal University of Pelotas, Southern Brazil.

Methodology: The study was conducted in an experimental orchard using young apple plants cultivar 'Eva'. Phenological data was obtained from four plants, of apical, median, and basal portions. The phenological stages adopted were 'C' (green tip), 'D' (half-inch green leafless), and 'F' (beginning of flowering). In order to determine water dynamics during dormancy stage and their fresh and dry weight, apple branches were collected and separated into three different tissues (bud, bark and wood) to evaluate water content.

Results: During the first growing season, there was a higher percentage of bud bursting in apical and median plant portion, while in the second season it was larger in middle and basal portion. Bark showed greater water content in most evaluations, while bud had increased water content in middle portion at the end of the dormancy stage, coinciding with the larger bud bursting.

Conclusion: Water content can be an indicator of overcoming endodormancy stage and bud bursting potential.