|Pitchay, Dharmalingam - UNIVERSITY OF TOLEDO|
|Gray, John - UNIVERSITY OF TOLEDO|
Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2005
Publication Date: July 17, 2005
Citation: Pitchay, D., Gray, J., Frantz, J., Horst, L., Krause, C.R. 2005. Do circadian rhythms accentuate k-deficiency in geranium? [abstract]. Hortscience. 40(4):132. Technical Abstract: Geranium (Pelargonium x hortorum) follows C3 metabolic pathway under normal environment. However, it switches to CAM metabolism under certain abiotic stress environments. This switch may affect the nutritional requirement and appearance of visible deficiency symptoms of these plants. Because potassium (K) plays a key role in stomatal function K-deficiency was studied in geranium. Plants were grown hydroponically in a glass greenhouse. The treatments consisted of a complete modified Hoagland s mM concentrations of macronutrients, 15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S, plus µM concentrations of micronutrients, 72 Fe, 9.0 Mn, 1.5 Cu, 1.5 Zn, 45.0 B, and 0.1 Mo, and an additional solution devoid of K. It took longer to develop the classical K deficiency symptoms than other bedding plant species commonly require. The K stress plants dry weight was 10 and 37% of control at incipient and advanced stage respectively. When portions of geranium leaves were covered, leaves with K stress developed rapidly (within 2 days) compared to the uncovered portion of the leaf blade. Control plants contained an abundance of marble-shaped K crystals in the adaxial surface of leaf mesophyll, but were lacking in the K-deficient plants. Geranium is prone to K stress during short days than long days and an additional supply K is needed for a normal growth under long night environment.