Patterns of on-shoot positioning of seed cones in relation to shoot length and position in the crowns of young Picea mariana

Abstract

Summary. Patterns of distribution of seed cones along the length and around the circumference of shoots were determined for young black spruce [Picea mariana (Mill.) B.S.P.] trees aged 9-17 years. Seed cone production averaged 5, 30, 62, 95, and 112 per tree of ages 9, 11, 13, 15, and 17 years, respectively. Cone distribution was restricted to distal and medial 1-year-old branches at age 9 and spread to distal 3-year-old branches by age 17. Sequentially, shoots of 0-25, 26-100, 101-250, 251-325, and 326-375 mm bore more cones in terminal, distal, medial, proximal, and basal positions along shoots, respectively. The uppermost and longest distal 1-year-old shoots bore most of their cones proximally and medially. On the shortest and innermost proximal order 2 shoots, cones were often terminal. The percentages of cones borne on upper, lower, and each of the two side surfaces of shoots were 31, 22, and 21, respectively, and 5% of the cones were terminal. Cones on lower surfaces were most common on the longest shoots near the apex of trees. Cones on upper surfaces became prevalent downward and outward in the crown. On-shoot positioning therefore varied in a predictable manner with shoot length, and thus with pattern of shoot-length distribution in the crown.

Location of cones in the crown and along shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) and the influence of coning intensity and shoot size

“…In addition, where female and male cones occurred together on equivalent shoot types, male cones tended to be borne more proximally on the bearing shoots than female cones. These patterns fit those described elsewhere for this and other species of Picea Molder 1976, 1977;Powell 1983;Marquard and Hanover 1984a;Longman 1985;Longman and Dick 1985;Lüscher 1989) and indeed match remarkably those presented for P. mariana at a comparable level of detail (Caron and Powell 1993).…”

“…On treated P. sitchensis grafts the distribution of lateral female, terminal female, lateral male, and terminal male cones showed a general progression from the upper distal to lower proximal regions in the crown (Dick et al 1994). This pattern is probably a reflection of the general progression of shoot vigour in the crown (Caron and Powell 1993) since, in general terms, female cones tend to be borne laterally on more vigorous shoots but more distally or terminally on less vigorous shoots Molder 1976, Powell 1983). A simple measure of shoot vigour is shoot length.…”

“…A simple measure of shoot vigour is shoot length. When cone position is related to shoot length it is found that the location of cones on the shoot tends to progress basipetally as bearing shoot length increases (Debazac 1965;Caron and Powell 1993;Powell 1995). In other words, cones tend to form in the "weakest" positions on the "strongest" shoots and vice versa (Caron and Powell 1993).…”

“…When cone position is related to shoot length it is found that the location of cones on the shoot tends to progress basipetally as bearing shoot length increases (Debazac 1965;Caron and Powell 1993;Powell 1995). In other words, cones tend to form in the "weakest" positions on the "strongest" shoots and vice versa (Caron and Powell 1993). The apparent equivalence of these positions may lend support to the suggestion that it is the vigour of the embryonic bud that determines the developmental pathway of the primordia (Anikeeva and Minina 1959;Tompsett 1978).…”

On buds man

“…In spruces, both seed-cone and pollen-cone buds can occur terminally or laterally, but how they are distributed differs with relative bearing-shoot vigour in each seed-cone and pollen-cone zone in the crown (Caron andPowell 1993, Powell 1995). On relatively long shoots, cones form in proximally to medially situated lateral buds (and sometimes basal buds if pollen cones).…”