Diagnosis device for environmental stress in plants and environmental stress diagnosis method

An environmental stress diagnosis device that diagnoses an environmental stress state of a plant sample, comprising:

• a measurement light source that radiates a measurement light to the plant sample;
• an induction light source that radiates a photosynthesis inducing light to the plant sample;
• a sealed chamber that stores the plant sample and allows entry of the measurement light and the photosynthesis inducing light;
• a transmitted light detector that detects the measurement light transmitted through the plant sample as a transmitted light, and a control unit that receives the transmitted light detected by the transmitted light detector as a measurement signal, wherein
• the measurement light source outputs two types of a first measurement light and a second measurement light having different wavelengths,
• the induction light source outputs two types of a first photosynthesis inducing light and a second photosynthesis inducing light having different wavelengths,
• the control unit has an analysis circuit that analyzes a detection result acquired by the transmitted light detector, and a control circuit that controls the measurement light source and the induction light source to correspond to the plant sample,
• the control circuit adjusts and controls the first measurement light and the second measurement light to have different output amplitudes, and controls the measurement light source such that the first measurement light and the second measurement light become opposite-phase rectangular waves,
• the control circuit controls the measurement light source to output the first measurement light and the second measurement light in synchronization to form the first measurement light and the second measurement light into a quasi-single composite rectangular wave measurement light of 5 kHz to 30 kHz including a DC component,
• the transmitted light detector detects the composite rectangular wave measurement light transmitted through the plant sample as a composite rectangular wave transmitted light,
• the analysis circuit calculates a light absorption difference between the first measurement light and the second measurement light transmitted through the plant sample by utilizing the composite rectangular wave transmitted light, and calculates Y(ND) which is a state in which P700 in photosystem I has been oxidized in photosynthesis as a ROS marker which is a reactive oxygen species suppression index for a plant by utilizing the light absorption difference, and
• the analysis circuit diagnoses the environmental stress state of the plant sample by utilizing the ROS marker.