Plant health diagnostic method and plant health diagnostic device

A plant health diagnostic device for diagnosing a health state of a plant in accordance with chlorophyll fluorescence emitted from chlorophyll of a plant body, the device comprising:

• fluorescence measurement means for measuring intensity of the chlorophyll fluorescence;
• and
• analysis means for evaluating the state of the plant in accordance with the chlorophyll fluorescence intensity measured by the fluorescence measurement means;
• wherein
• the analysis means
• obtains a first minimum point after a maximum point having largest chlorophyll fluorescence intensity and a first maximum point after the minimum point on a time course curve of the chlorophyll fluorescence intensity measured by the fluorescence measurement means,
• defines chlorophyll fluorescence intensity values at the minimum point and the first maximum point after the minimum point as S and M, respectively,
• obtains a value M/S from the values S and M, and
• evaluates an initial state of photosynthetic functional disorder of the plant body with use of the value M/S and a value M/S of a healthy site of a plant body or of a healthy plant individual body as a reference value.

A plant health diagnostic method of diagnosing a health state of a plant in accordance with chlorophyll fluorescence emitted from chlorophyll of a plant body, the method comprising:

• obtaining a first minimum point after a maximum point having largest chlorophyll fluorescence intensity and a first maximum point after the minimum point on a time course curve of the chlorophyll fluorescence intensity;
• defining chlorophyll fluorescence intensity values at the minimum point and the first maximum point after the minimum point as S and M, respectively;
• obtaining a value M/S from the values S and M;
• discriminating a leaf portion and a stem portion in the plant with use of the value M/S;
• and
• diagnosing a growth state of the plant in accordance with a stem diameter of the discriminated stem portion.