Seasonal Variations in Reserve and Structural Components of Pinus Resinosa Cones

Changes in reserve materials, lignin, hemicellulose, and cellulose of 1st‐year conelets and 2nd‐year cones of red pine (Pinus resinosa Ait.) were studied by chemical extraction of the respective fractions. During the first 11 months after emergence of conelets, reserve materials, primarily carbohydrates, constituted approximately half of the dry weight of cones. Cellulose and hemicellulose contents were low but cells were highly lignified. During summer of the 2nd year of cone development, marked compositional changes occurred. A rapid surge of cone growth, possibly triggered by resumption of pollen‐tube growth and fertilization, occurred from mid‐June to early August and was accompanied by transformation of reserve materials into cellulose and, to a lesser extent, into hemicellulose and lignin. During this transformation, the thickening and lignification of cells responsible for the opening of cone scales probably occurred. The developing seeds also mobilized readily available cone reserves during this time.