Multi-sensor monitoring for temperature stress evaluation of broccoli (Brassica oleracea var. italica)

Several sensors have been developed for soil and plants to assess plant stress due to climate change.Therefore, the objective of the study is to nondestructively evaluate temperature stress on plant by monitoring climatic and soil conditions and plant responses using various sensors.Plant responses were monitored by electrical conductivity in plant stem and sap flow rate.Electrical conductivity in plant stem reflects the physiological activity of plants including water and ion transport.Fully grown Brassica oleracea var.italica was exposed to 20/15 o C (day/night) with 16 h photoperiods as a control, low temperature 15/10 o C, and high temperature 35/30 o C while climatic, soil, and plant conditions were monitored.Electrical conductivity in plant stem and sap flow rate increased during the day and decreased at night.Under low temperature stress, electrical conductivity in plant stem of Brassica oleracea var.italica was lower than control while under high temperature stress, it was higher than control indicating that water and ion transport was affected.However, chlorophyll a and b increased in leaves subjected to low temperature stress and there was no significant difference between high temperature stressed leaves and control.Free proline contents in the leaves did not increase under low temperature stress, but increased under high temperature stress.Proline synthesis in plant is a defense mechanism under environmental stress.Therefore, Brassica oleracea var.Italica appears to be more susceptible to high temperature stress than low temperature.