Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2008
Publication Date: 12/3/2009
Citation: Raese, T., Curry, E.A. 2009. Bioregulators Influence Calcium Concentration and Cold Hardiness of Young "Delicious" (Malus Domestica, Borkh) Apple Trees. Journal of Plant Nutrition. 33:1-9.
Interpretive Summary: Freeze injury to fruit trees in central and eastern Washington state may occur from Nov to Mar; but Dec is most often associated with severe injury from sub-freezing temperatures. Our previous work indicates cold hardiness in apple trees may be improved by whole-tree calcium sprays. Moreover, certain bioregulators and plant protectants have shown consistent promise for reducing risk of tree injury due to cold temperatures. The objective of this work was to determine if improved cold hardiness of young apple woody tissue by fall application of bioregulators or plant protectants was correlated with increases in mineral element content, especially calcium. Young 'Delicious' apple trees were treated in late Sep and/or late Oct by topical application of ProTec™ (protectant) at 5 or 10%, and/or Pix™ (bioregulator) at 0.05%. Cold hardiness and mineral composition were evaluated monthly from Nov to Mar. Applied in Oct, Pix™ resulted in woody tissue with the highest cold hardiness rating from Nov through Mar. From Oct 28 through Dec 8, tissue from control trees had the lowest calcium concentration and frequently the least amount of cold hardiness. In woody stems of young apple trees, cold hardiness was more closely related to calcium concentration than the other eleven measured mineral elements.
Technical Abstract: Calcium concentration and cold hardiness in woody shoots of young 'Delicious' apple trees increased during the first half of the dormant season by early-fall whole-tree application of bioregulators and/or plant protectant. Compared with untreated controls, the plant protectant, a-[(1,3-dioxolan-2-ylmethoxy) imino] benzene acetonitcile (Hytech Polymer, [formerly ProTec™], Agro-K, Corp., Minneapolis, MN) applied in Sep at 5 or 10% induced more cold hardiness in late Oct and Nov, whereas treating at 0.05% with the bioregulator, 2-chloroethyl-methyl-bis(phenylmethoxy)silane (CGA-15281, Novartis International AG, formerly Pix™, Ciba-Geigy Limited, Basel, Switzerland), induced greater cold hardiness and higher woody tissue calcium concentration in Nov and Dec. Applied in Oct, CGA-15281 resulted in woody tissue with the highest cold hardiness rating from Nov through Mar. From Oct 28 through Dec 8, tissue from control trees had the lowest calcium concentration and frequently the least amount of cold hardiness. In woody stems of young apple trees, cold hardiness was more closely related to calcium concentration than the other eleven measured mineral elements, especially from Nov to Mar (r = -0.856).