From the Field-Agronomy Notes

(Updated: Aug. 8, 2016, 1:03 p.m.)

Tobacco Research Update: Potassium Deficiency of Tobacco

In this tobacco research update, we highlight the symptoms of potassium deficiency.  These images are part of a project supported by the North Carolina Tobacco Foundation to develop a web-based diagnostic key for the identification of nutrient disorders of tobacco.

Potassium (K) is one of the three core macronutrients, and consequently, deficiency symptoms manifest relatively quickly in tobacco.  Potassium is a mobile element, which means it will translocate from mature tissues to the younger tissue where it is needed.  This movement of K from older to younger foliage is what causes deficiency symptoms to develop first on the lower foliage.

Potassium deficiency symptoms begin as a mild chlorosis and mottling of the leaf margin.  Since K is vital to leaf expansion, the edge of the foliage curls in and downward, resulting in an umbrella like shape (Fig. 1).  In addition to marginal interveinal chlorosis, mottling, and leaf deformation, a K stressed plant exhibits a general stunting of growth (Fig. 2).

Figure 1. Initial K deficiency in the lower foliage, note the umbrella shape of the leaf margin. ©2016 Forensic Floriculture
Figure 1. Initial K deficiency in the lower foliage, note the umbrella shape of the leaf margin.
©2016 Forensic Floriculture

As K starvation continues, interveinal chlorosis and mottling advance from the leaf margin moving toward the center.  As symptoms progress, the marginal spots will expand in size and eventually become necrotic (Fig. 3).

Figure 2. A healthy tobacco plant on the left as compared to a K deficient plant on the right. ©2016 Forensic Floriculture
Figure 2. A healthy tobacco plant on the left as compared to a K deficient plant on the right.
©2016 Forensic Floriculture
Figure 3. Intermediate K deficiency, note the marginal necrotic spots and advancing interveinal chlorosis. ©2016 Forensic Floriculture
Figure 3. Intermediate K deficiency, note the marginal necrotic spots and advancing interveinal chlorosis.
©2016 Forensic Floriculture

When tobacco experiences a severe potassium deficiency, “firing” symptoms will appear.  This unique and fascinating indicator appears as extremely chlorotic or even blanched foliage that is brittle in texture and appearance (Fig. 4).  The fired leaves may experience loss of leaf tissue as the brittle, necrotic tissue breaks away.  As potassium deficiency persists, the symptoms will continue up the plant into the next level of foliage.

Figure 4. Firing of the lower leaves, note progression of symptomology (firing and blanching, sever chlorosis and necrosis of the margin, and beginning yellowing of the leaf margin) as it moves up the plant. ©2016 Forensic Floriculture
Figure 4. Firing of the lower leaves, note progression of symptomology (firing and blanching, sever chlorosis and necrosis of the margin, and beginning yellowing of the leaf margin) as it moves up the plant.
©2016 Forensic Floriculture

We would like to express our appreciation to the North Carolina Tobacco Foundation for supporting this project. We will be providing updates as symptoms progress over the course of the nutrient disorder induction phase of the experiment.

Figure 5. The 360-degree view of this symptomatic plant with a severe potassium deficiency may be viewed by clicking on the above picture. ©2016 Forensic Floriculture
Figure 5. The 360-degree view of this symptomatic plant with a severe potassium deficiency may be viewed by clicking on the above picture.
©2016 Forensic Floriculture

Key Contact: Dr. Matthew Vann, Department of Crop and Soil Science mcvann@ncsu.edu

Contributing Authors: Paul Cockson, Josh Henry, Matthew Vann, and Brian Whipker

Funding Source: North Carolina Tobacco Foundation

Project Team: Josh Henry (NC State M.S. student in Horticultural Science), Paul Cockson (NC State B.S. student in Agroecology), Ingram McCall (Research Technician in Horticultural Science), Rhonda Conlon (Extension IT at NC State), Matthew Vann (Tobacco Extension Specialist, Dept. of Crop and Soil Science), and Brian Whipker (Professor of Floriculture and Plant Nutrition in Horticultural Science).

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