Winter Rye Leaf Emergence and its Relationship to the Phyllochron

Abstract

Winter rye (Secale cereale L.) is a high‐tillering cereal crop. Understanding the relationship between the phyllochron for mainstem leaves and that of tillers is useful in adequately describing plant development and selecting crop management strategies. This study was conducted to determine the phyllochrons of conventional height (CH) and semidwarf (SD) genotypes of winter rye and the relationship of the phyllochron of mainstem leaves to that of primary tillers. Three CH and two SD genotypes were planted in a controlled‐environment growth room. Leaf stages were determined with the Haun scale and the phyllochron calculated as the inverse of the slopes of linear regressions of Haun stage to growing degree‐days (GDD). For both CH and SD genotypes, the Haun stage increased linearly with GDD, and the phyllochron was constant in the pre‐vernalization (0 < GDD ≤ 266) and vernalization (266 < GDD ≤ 566) periods. During post‐ vernalization (566 < GDD ≤ 914), the phyllochron for the mainstem increased with GDD. Leaves on the coleoptile tiller (TO), T1 (the tiller from leaf no. 1 of the mainstem), and T2 had mean phyllochrons similar to that for the mainstem. Leaves on higher positioned tillers (T4, T5) had greater phyllochron than the earlier tillers. The higher positioned tillers also required more thermal time units to emerge than the earlier tillers. To precisely describe winter rye development using the phyllochron, one should consider that the phyllochron changes with leaf and tiller position on the culm.