The Nutrient Status of Zinc in Lettuce Evaluated by Plant Analysis1

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Abstract
Lettuce was grown in a complete nutrient solution, with Zn increased stepwise by a factor of 2 for 8 treatments from 1.6 to 200 μg/liter. Forty-seven days after imbibition the plants were harvested and separated into 6 parts for tissue analysis. The plants in the low Zn solutions were stunted in growth and showed a marginal purpling and a rupture of laticifers on the margins of the mature leaves. The symptoms progressed from an overall chlorosis to an interveinal necrosis; with the dark desiccated areas eventually coalescing to cover most of the leaf. The Zn nutrient status of the lettuce plant was best defined by determining the Zn concentration in the mature petiole (mid-rib). The critical level of Zn in the mature petiole is 9 ppm. Concentration of Zn in this tissue below 9 ppm indicates an unfavorable Zn nutrient status for the vegetative growth of lettuce.