Lower Basal Temperature and Thermal Sum of the Arugula in Conventional and Hydroponic Production Systems

Abstract Among the environmental factors that influence plant growth, one of them is the air temperature. The plant growth rate can be determined through its lower basal temperature (Tb), which corresponds to the temperature below which the leaf expansion rate is negligible or occurs in a reduced way. This work aimed to determine Tb and the thermal sum (ST) of the ‘Rococó’ arugula during the time period comprising germination and harvest in conventional and hydroponic production system. The experiment took place in Florianópolis, from April 2018 to March 2020, totalizing five and seven harvests in the conventional and hydroponic production system, respectively. The Tb was obtained by using the average of three methods, namely: least standard deviation in days, relative development and the regression coefficient. With the Tb value, the thermal sum (ST) was determined using the simplified degree-day method for each harvest. From the ST determined values, an average was obtained to establish the ST of the arugula. During the period comprising germination and harvest, considering the conventional and hydroponic production systems, obtained values of Tb were respectively 4,4 and 3,6 °C whereas the ST were 559 and 490 accumulated degree-day.