Location: Biological Control of Pests ResearchTitle: Use of an inexpensive chlorophyll meter to predict Nitrogen levels in leaf tissues of water hyacinth (Eichhornia crassipes (Mart.) Solms
|HARMS, NATHAN - Us Army Corp Of Engineers (USACE)|
|FREEDMAN, JAN - Us Army Corp Of Engineers (USACE)|
Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2016
Publication Date: N/A
Interpretive Summary: A cheaper and less invasive method for determining chlorophyll and indirectly nitrogen levels in plant leaves was tested and found comparable to more expensive units with similar if not more accurate capability. This allows rapid determination of nitrogen which is often a good predictor of plant health.
Technical Abstract: Tissue nitrogen is also an important indicator of plant health and can be a useful predictor of plant vigor and susceptibility to disease and pests. Hence, knowing nitrogen content may aid in determining establishment success of plants used in restoration programs, including those destined for aquatic and wetland sites as well as an indicator of biological control herbivore success. However, most techniques used to determine plant nitrogen content require destructive, lengthy, and expensive chemical analyses which often preclude their use on a routine basis. A non-destructive procedure is needed that provides actual readings of tissue nitrogen on a near real-time basis. Techniques have been developed that allow real time analysis of plant tissue chlorophyll levels. These include the use of hand-held meters that measure light transmittance of leaves allowing a determination of the ‘greenness’ of the plant, which has been shown to be proportional to chlorophyll content. Since chlorophyll and nitrogen content are closely related, a rapid method of estimating nitrogen in plants is available. More recently, a chlorophyll meter (atLeaf+) has become available which has been shown to be highly accurate in predicting plant nitrogen content but considerably lower in cost relative to other devices costing much more. The utility of using the these less expensive chlorophyll meters to predict leaf nitrogen content in aquatic plants has not been evaluated; hence, we tested its use to determine chlorophyll levels in Eichhornia crassipes (Mart.) Solms (water hyacinth) leaves and assess its predictability in estimating nitrogen content. The atLeaf+ meter was used to determine ‘greenness’ (proportional to chlorophyll) of water hyacinth leaf tissues during a greenhouse-based experiment designed to examine the influence of temperature on the survival of the water hyacinth planthopper (Megamelus scutellaris Berg). A significant (p < 0.05, r = 0.839) positive correlation was detected between predicted chlorophyll values and actual nitrogen levels in water hyacinth above-water biomass (Fig. 1). Greater than 70% of the variation in mean nitrogen levels can be explained by the linear relationship between estimated chlorophyll and actual plant nitrogen content. The largest source of unaccounted variation between predicted chlorophyll and nitrogen is believed to be related to the plant parts used in the determination of nitrogen in this experiment. Nitrogen was measured on the entire above-water biomass (including leaves and petioles), in contrast to the atLeaf+ measurements which were taken only on leaf tissue. Water hyacinth petioles generally contain significantly lower chlorophyll and nitrogen content in comparison to leaf tissues.