Water relations, cuticular transpiration, and bud characteristics of air-slit containerized Picea glauca seedlings in response to controlled irrigation regimes

White spruce seedlings (Picea glauca (Moench) Voss) were grown in air-slit containers (IPL 25-350A) in a tunnel under four different irrigation regimes (IR-15%, IR-30%, IR-45%, and IR-60%, v/v; (cm H2O)3·(cm substrate)–3). At the end of the first growing season the water-relation variables of the shoots were determined. Seedling morphology, the rates of cuticular transpiration and terminal bud development, as well as the number of needle primordia were also measured. Irrigation regime had no significant effect on any of the water-relation variables. Seedlings grown under the IR-15% were smaller and completed bud development more quickly than seedlings grown under IR-30%, IR-45%, and IR-60%. The formation of needle primordia was enhanced under IR-30%. Both the irrigation regime and the amount of time the detached shoots were left to transpire had a significant effect on the rate of cuticular transpiration. A comparison of the water-relation variables at the end of the first (1998) and second (1999) growing seasons showed that the younger seedlings had more negative osmotic potential at tissue saturation and greater maximum modulus of elasticity values. None of the other water-relation variables were significantly affected by seedling age, but the absolute values of all the variables were greater in the younger (1+0) seedlings.

Parental environment aftereffects on germination, growth, and adaptive traits in selected white spruce families

Seed orchards for the production of conifer seed in British Columbia are usually located in areas favorable (warm and dry) for flowering and seed development, often considerably south of the source location of the parent trees. Differences in environmental conditions between seed orchard location and location of origin can affect progeny performance. It is suspected that this is caused by environmental factors that affect reproductive processes of parent trees and lead to altered physiological traits (aftereffects). This study examined if aftereffects are present in white spruce (Picea glauca (Moench) Voss). Control pollinations were made at two locations, Red Rock, near Prince George (53°N) in central British Columbia, and Kalamalka, near Vernon (50°N) in southern British Columbia, on five female trees using a four-male polymix. Identical genotypes through grafting were present at the two locations. Pollen maturing at each site was only used in the polymix at that particular location. Progeny were raised and germination traits, number of needle primordia, greenhouse and field heights, and frost hardiness were evaluated in a common environment. The location of seed development significantly affected all traits evaluated. Height growth aftereffects in the second field season were much less than those observed in the first field season. These results suggest that aftereffects are detectable in white spruce progeny performance in British Columbia.

How to identify bud initiation and count needle primordia in first-year spruce seedlings

Bud initiation and subsequent bud development are key steps in the nursery production of first-year temperate spruce seedlings for reforestation. An understanding of the bud initiation and development processes and monitoring methods are of vital importance to both tree seedling nursery workers and foresters. A review of bud morphology and the bud development process is given for spruce seedlings. The equipment required and techniques used in the determination of bud initiation, and estimation of the number of needle primordia are presented. When properly applied, the examination of spruce buds forms a cornerstone for successful nursery management using extended greenhouse culture. Key words: bud initiation, bud morphology, bud dissection, black spruce, Picea mariana, needle primordia, nursery management

The effects of summer shoot production on height growth components of seedlings of California red and white fir

Morphogenesis of the terminal shoot was studied in 2-year-old seedlings of California red fir (Abiesmagnifica A. Murr.) and two elevational sources of white fir (Abiesconcolor (Gord. & Glend.) Lindl.). Seedlings were either watered or left unwatered during the growing season in order to produce different shoot morphologies and seedlings with and without a summer shoot. Under favorable soil moisture, the frequency of summer shoot production was 32, 53, and 82% for red fir and high- and low-elevation white fir, respectively. Drought from mid-May to mid-September reduced summer shoot production to less than 1% in both species. Spring shoot morphology was not an indicator of capacity to produce a summer shoot. Rate of primordium production was directly related to apical dome diameter. However, when the normal spring increase in apical dome diameter was arrested by summer shoot elongation, the rate of primordium production appeared to be unaffected. Although the apical and subapical meristems were active at the same time, they did not appear to be antagonistic. The major effects of producing a summer shoot were as follows: (i) elongation of 60–120% more intemodes in the current growing season, (ii) production of 15–40% more needle primordia in the overwintering bud, (iii) production of 30–60% more primordia annually, and (iv) increase in the percentage of total primordium production that developed into needles from 60% to 75–80%.

Influence of dormancy induction treatments on western hemlock seedlings. I. Seedling development and stock quality assessment

Western hemlock (Tsugaheterophylla (Raf.) Sarg.) seedlings were grown in a greenhouse and subjected to four dormancy induction treatments (DIT) (i.e., long-day dry, long-day wet, short-day dry, and short-day wet) during midsummer. In the late summer and fall, seedling development was monitored and it was found that (1) short-day DIT caused a rapid cessation of shoot growth; (2) short-day DIT caused rapid fall development of needle primordia, while long-day DIT took until midwinter to produce the same number of needle primordia; and (3) short-day DIT seedlings had lower saturated and turgor loss point osmotic potentials and greater maximum modulus of elasticity in October than long-day DIT. Seedlings were tested with a comprehensive stock quality assessment procedure just before late winter field planting. These tests showed the following: (1) morphological parameters: short-day DIT reduced shoot to root ratios; (2) pressure–volume analysis: short-day wet seedlings had the lowest osmotic potentials at saturation and turgor loss point; (3) soluble sugar analysis: greater levels of total soluble sugars were found in non water stressed DIT compared with water stressed DIT seedlings; (4) seedling water movement: short-day DIT seedlings had the lowest resistance to water movement at low root temperature (5 °C); (5) low root temperature response: short-day compared with long-day DIT seedlings had greater photosynthesis and stomatal conductance at low root temperatures; (6) root growth capacity: seedlings from all DIT were capable of growing roots at optimum root temperature (22 °C), but short-day compared with long-day DIT had greater root growth at low root temperatures; (7) drought stress response: short-day wet seedlings had the highest photosynthesis and stomatal conductance levels as predawn shoot water potentials decreased; and (8) frost hardiness: short-day wet seedlings had the least needle damage when tested at temperatures of −15 and −18 °C.

Differentiation of bud meristems and cataphylls during adventitious bud formation on embryos of Picea abies

Embryos of Picea abies were pulse-treated with benzyladenine for 24 h and then cultured on medium lacking growth regulators. Meristemoids developed on all embryos during the 2nd week after the cytokinin treatment. Cells within the meristemoids divided randomly. As the meristemoids developed, further cell divisions became more organized so that separate regions of meristematic activity could be distinguished within each meristemoid. These meristematic regions developed into individual nodules and each nodule developed further into either a bud meristem or a cataphyll. Cataphylls were composed of unorganized, vacuolated, thick-walled cells whereas bud meristems were composed of organized meristematic cells. Later, xylem elements developed at the base, and needle primordia at the top of bud meristems. The bud apex had cytohistological zonation typical of conifers. The appearance of the developing adventitious buds depended on the number of cataphylls formed per bud as well as on the marginal expansion of the cataphylls.

Control of height growth components in seedlings of California red and white fir by seed source and water stress

Terminal bud growth in 2nd-year seedlings and subsequent elongation of the overwintering bud in the 3rd year were studied in California red fir (Abiesmagnifica A. Murr.) and two elevational sources of white fir (A. concolor (Gord. and Glend.) Lindl.). During each growing season the seedlings were either watered or left unwatered to provide 2nd and 3rd year treatments of wet–wet, dry–wet, wet–dry, and dry–dry seasons. Harvests were done biweekly during the second growing season and once at the end of the third growing season. Rate and duration of primordium production were negatively related and there were no differences among seed sources for the number of primordia produced in the 2nd year. Watering more than doubled the number of primordia, mainly through increasing the rate of production. Internode number and length were negatively related on a genetic and environmental basis. Changes in internode length tended to compensate for environmentally induced changes in internode number which resulted in a year to year stability in height growth. Height growth was more buffered against changes in internode number in red fir than in white fir. Watering induced a summer shoot in 80% of low-elevation white fir seedlings and 40% of red fir and high-elevation white fir seedlings. Summer shoots doubled the height increment for the current season and increased the number of needle primordia in the winter bud by 26%. The larger buds were the result of a prolonged period of primordium production.

Gibberellin A4/7 enhances seed-cone production in field-grown black spruce

Black spruce (Piceamariana (Mill.) B.S.P.) grafts growing in a seed orchard were sprayed with gibberellin A4/7, and grafts and trees in families growing in arboreta were sprayed with gibberellin A4/7 and (or) vitamin E from vegetative bud burst to the end of shoot elongation. Gibberellin A4/7 was very effective in promoting seed cones and 400 mg/L appeared optimal. Vitamin E at 1000 mg/L was not effective. Vegetative bud burst occurred in mid-May and shoot elongation ended in late June. Needle primordia were visible on the apices of newly formed buds at the end of June. Reproductive buds had fewer bud scales than vegetative buds. It appeared that potential reproductive buds terminated their bud scale initiation earlier. Gibberellin A4/7 application to promote seed-cone production should be carried out before bud-type differentiation. This coincides with the end of lateral shoot elongation.