Castagno: un primo approccio alla fisiologia di crescita del riccio.

The seasonal and daily growth of sweet chestnut (C. sativa Mill.) husks have been studied in a commercial orchard in Monterenzio (Bologna, Italy). The seasonal growth pattern in the maximum and minimum diameter of 20 husks were measured every 7 days from 30 days after full bloom (DAFB) - corresponding at the beginning of June - to a week before harvest (120 DAFB). The absolute and relative growth rate (AGR, RGR) have also been calculated. Growth of 6 husks was monitored from the 4th to the 11th of August 2017 through very precise fruit gauges, connected to a custom-built, Arduino-based data logger, which was monitored through a wireless network (AWSN). The 6 husks were selected on 3 trees (2 husks per tree) and their diameters were recorded every 15 minutes for the entire week. Temperature (0C) and daily precipitation (mm/day) were sourced from a close (2 km) meteorological station belonging to ARPAE (Regional agency for environmental control). The husk exhibited a seasonal diameter growth pattern resembling a double sigmoid. AGR responded positively to rainfalls, as no irrigation was provided. Interestingly, daily husk growth started mid-morning and continued till dark (from 10:00 to 21:00), followed by shrinkage during night-time. This pattern of growth appears opposite if compared to other fruit species as Prunus persica L. or Malus domestica Bork., which exhibit growth during the last part of the day/night and shrinkage/no growth during the day. Our data show a quick increase (within the following 24 hours) in husk growth rate after a rainfall event. These preliminary data show the need for further studies on C. sativa physiology and their potential impact on improving irrigation practices for this intriguing crop.