Chlorophyll fluorescence as a tool for nutrient status identification in rapeseed plants

Area of Science:

• Plant Physiology
• Biochemistry
• Environmental Science

Background:

• Plant growth and development are critically dependent on soil micro- and macroelement availability.
• Assessing plant nutrient status requires examining combined deficiencies, not just single ones, as these significantly affect photosynthesis.
• Nutrient imbalances disrupt the photochemical processes essential for plant growth.

Purpose of the Study:

• To establish a connection between soil and plant leaf elemental content and chlorophyll a fluorescence parameters.
• To develop a method for the early detection of plant stress caused by combined nutrient deficiencies under natural conditions.
• To explore the utility of machine learning in analyzing plant physiological responses to nutrient status.

Main Methods:

• Utilized a mathematical procedure combining Principal Component Analysis (PCA), hierarchical k-means clustering, and Super-Organising Maps (SOMs).
• Analyzed elemental content in soils and plant leaves alongside selected chlorophyll a fluorescence parameters.
• Classified plant responses into five distinct groups based on chlorophyll fluorescence patterns.

Main Results:

• Significant differences in mineral content correlated with functional changes in the photosynthetic machinery, measurable via chlorophyll fluorescence.
• Five distinct chlorophyll fluorescence patterns were identified, corresponding to 'no deficiency', Fe-specific deficiency, and varying levels of general deficiency (slight, moderate, strong).
• Nutrient deficiencies, particularly severe ones, led to suboptimal development of Photosystem II (PSII) and Photosystem I (PSI), affecting antenna complex organization and specific fluorescence parameters (e.g., increased Fo, ΔV/Δt₀; decreased φPo, φEo, δRo, φRo).

Conclusions:

• Chlorophyll fluorescence, when analyzed with machine learning techniques, provides a highly informative method for assessing plant nutrient status.
• This combined approach can effectively detect plant stress resulting from combined nutrient deficiencies.
• The chlorophyll fluorescence method offers a potentially faster and less resource-intensive alternative to chemometric analyses for diagnosing plant nutrient issues.