n Southern African Forestry Journal - Using chlorophyll fluorescence to determine stress in seedlings : scientific paper




Since several environmental factors affect the functioning of the photosynthetic system, the status of the photosynthetic apparatus is a good indicator of the plant in terms of stress and stress adaptation. The measurement of chlorophyll fluorescence with a portable fluorimeter has been shown to be a useful non-destructive method for the investigation of the structure and function of the photosynthetic apparatus. A quantitative analysis of fluorescence emission, called the JIP-test, has also been introduced by which the behaviour of the photosynthetic system in response to environmental changes can be monitored. A pilot trial was conducted to determine the effect of light, water and nutrient stress on the fluorescence emission of <I>Eucalyptus grandis&lt;/I&gt; seedlings. Flourescence measurements were made on potted plants with a Hansatech Plant Efficiency Analyser, every one to two days from stress initiation until trial termination. The results indicate that water and light stress in <I>E. grandis&lt;/I&gt; seedlings can be detected using chlorophyll fluorescence data. The quantum efficiency of primary photochemistry (F<sub>v</sub>/F<sub>m</sub>) is a good indicator of water stress, while a more detailed analysis of the JIP-test parameters is required for detection of light stress. These results indicate that nutrient stress may have to be severe before photosynthesis and growth are affected. As a practical tool to detect unhealthy plants this technique could be useful to the forestry industry particularly in the fields of establishment and tree breeding where drought or temperature stressed seedlings could be detected before mortality occurs. More detailed studies are required to confirm this.


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