Showing papers by "Timothy J. Tschaplinski published in 1991"
TL;DR: Western hemlock seedlings were grown in a greenhouse and subjected to four dormancy induction treatments (DIT) during midsummer and it was found that short-day DIT caused a rapid cessation of shoot growth and rapid fall development of needle primordia.
Abstract: 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 satu...
51 citations
TL;DR: The osmotic potential at the turgor loss point ( ψπTLP) decreased in shoots and roots of water-stressed seedlings of both species, resulting in the maintenance of positive turgors at lower xylem water potentials (ψX) compared with nonstressed Seedlings.
Abstract: Water potential components and organic solutes were examined in shoots and roots of potted jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) seedlings after exposure t...
41 citations
TL;DR: Photosynthetic pigment concentrations and net photosynthetic rate were the most sensitive indicators of growth response to nitrogen fertilization in the first growing season, suggesting careful timing of low level applications of nitrogen fertilizer can optimize growth.
Abstract: American sycamore (Platanus occidentalis L.) seedlings were grown in the field under different urea-nitrogen fertilization regimes to identify physiological variables that characterize the growth response. Treatments included fertilization at the beginning of the growing season with 50, 150, 450 kg N ha−1, fertilization 3 times each at 37.5 kg N ha−1 and unfertilized control. The greatest aboveground biomass accumulation (3× that of control) occurred in plots fertilized with 450 kg N ha−1, but nearly as much growth occurred when 37.5 kg N ha−1 was added periodically. Photosynthesis, chlorophyll concentrations and growth increased rapidly after the midseason application of 37.5 kg N ha−1 but not after the late-season application. Although nitrogen fertilization increased leaf area per plant, leaf nitrogen concentration did not differ between treatments. There was no evidence to indicate that fertilization extended the physiologically active season or increased susceptibility to drought or cold. Sycamore leaves accumulated sucrose and mannose in response to water stress in all treatments. Photosynthetic pigment concentrations and net photosynthetic rate were the most sensitive indicators of growth response to nitrogen fertilization in the first growing season. Careful timing (based on physiological indicators) of low level applications of nitrogen fertilizer can optimize growth.
17 citations
14 citations