VARIATIONS IN SAP FLOW DURING FLORAL FORMATION AND DEVELOPMENT IN HAZELNUT (CORYLUS AVELLANA L.)
European hazelnut (Corylus avellana L.) is characterized by early bloom of catkins that start to shed pollen, depending on the variety, from the end of December to mid February; while female flowers become receptive from the beginning of January towards the end of February. During the development of the flowers, plant is leafless and transpiration is negligible. Winter low temperatures might lead to ice formation in the conductive tissue blocking water flux to developing floral tissues. The aim of this work was to assess whether there is any sap flow detectable in the stem during the phase of catkin extension; moreover it was determined if the sap flow, recorded with instrumental monitoring, allowed to substitute weekly phenological observations in the evaluation of the development of the catkins. We measured the variation of sap flow by using Graniers sensors during winter on three hazelnut plants located in Piedmont Region (Northern Italy). We monitored, air temperature and the most important meteorological variables using a standard weather station. Phenology of the catkins was recorded weekly as the length of 20 catkins selected and previously marked on each plant. Results showed that rate of floral tissue extension is higher during the warmer winter days, suggesting that floral development needs to be supplied with a certain amount of water. Variations of stem temperature and sap flow showed that freezing-thawing cycles during floral formation occurred and that the maximum rate of floral extension is related to stem thawing conditions.
Pisetta, M., Carraro, V. and Anfodillo, T. (2011). VARIATIONS IN SAP FLOW DURING FLORAL FORMATION AND DEVELOPMENT IN HAZELNUT (CORYLUS AVELLANA L.). Acta Hortic. 922, 177-182
catkin development, Sap flow, phenology, floral extension, freeze/thaw cycles