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PubMed1994

Crown architecture of understory and open-grown white pine (Pinus strobus L.) saplings.

Crown architecture and growth allocation were studied in saplings of eastern white pine (Pinus strobus L.), a species classified as intermediate in shade tolerance. A comparison was made of 15 understory saplings and 15 open-grown saplings that were selected to have comparable heights (mean of 211 cm, range of 180-250 cm). Mean ages of understory and open-grown trees were 25 and 8 years, respectively. Understory trees had a lower degree of apical control, shorter crown length, and more horizontal branch angle, resulting in a broader crown shape than that of open-grown trees. Total leaf area was greater in open-grown saplings than in understory saplings, but the ratio of whole-crown silhouette (projected) leaf area to total leaf area was significantly greater in understory pine (0.154) than in open-grown pine (0.128), indicating that the crown and shoot structure of understory trees exposed a greater percentage of leaf area to direct overhead light. Current-year production of understory white pine was significantly less than that of open-grown white pine, but a higher percentage of current-year production was allocated to foliage in shoots of understory saplings. These modifications in crown structure and allocation between open-grown and understory white pine saplings are similar to those reported for more shade-tolerant fir (Abies) and spruce (Picea) species, but the modifications were generally smaller in white pine. As a result, white pine did not develop the flat-topped "umbrella" crown structure observed in understory fir and spruce, which approaches the idealized monolayer form that maximizes light interception. The overall change to a broader crown shape in understory white pine was qualitatively similar, but much more limited than the changes that occurred in fir and spruce. This may prevent white pine from persisting in understory shade as long as fir and spruce saplings.

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PubMed1994

Variation in foliar delta(13)C values within the crowns of Pinus radiata trees.

Although herbaceous species generally show little within plant variation in delta(13)C, trees show large spatial and temporal differences. We found that the aspect of exposure and branch length accounted for up to 6 per thousand delta(13)C difference within the foliage of individual trees of Pinus radiata D. Don. The foliage on branches 0.5 m in length was as much as 4 per thousand more depleted in (13)C than foliage on 10-m long branches, and an additional 2 per thousand more depleted on the shaded side than on the exposed side. We confirmed that on clear days, relative branch hydraulic conductivity, defined as the ratio of transpiration to the water potential gradient, was much higher in short branches than in long branches. Stomatal conductance remained high in foliage on short branches during the day, whereas it declined progressively in long-branch foliage under similar conditions. These differences were sufficient to explain the observed variation in delta(13)C in foliage on long and short branches.

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PubMed1994

Steady-state nutrition of Pinus resinosa seedlings: response to nutrient loading, irrigation and hardening regimes.

To test effects of fertilization on late-season growth and nutrient content of container-grown red pine (Pinus resinosa Ait.), seedlings were subjected to a factorial combination of two fertilization regimes (exponentially increasing concentrations providing 25 (1N) and 75 (3N) mg N seedling(-1), respectively) and two irrigation regimes (well-watered and water-stressed) followed by drought-hardening or nonhardening. The fertilization treatments gave rise to steady-state nutrition in the seedlings during the prehardening phase. The 3N treatment increased macronutrient uptake significantly more than dry matter production, particularly in the roots, giving rise to what has been called luxury consumption of nutrients, or nutrient loading. Nutrient loading was higher in well-watered seedlings than in water-stressed seedlings. Among well-watered seedlings, relative growth rate of nutrient-loaded seedlings was more sensitive to drought during the hardening phase than that of nonloaded seedlings. However, when watering was resumed at the end of the hardening treatment, the relative growth rate of the nutrient-loaded seedlings (421%) exceeded that of the nonloaded seedlings (213%). Nitrogen accumulation was also higher in nutrient-loaded seedlings than in nonloaded seedlings during the post-hardening phase.

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PubMed1994

2S Arginine-rich proteins from Pinus pinaster seeds.

Low molecular weight globulins, which are abundant proteins in the Pinus pinaster Ait. megagametophyte, were purified and characterized. They showed a dimeric structure formed of one large and one small subunit linked by disulfide bridges. They were characterized by a high Arg and Glx content and by a relatively high Cys content. A comparison of their characteristics with those of angiosperm 2S proteins suggests that there is homology between them.

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PubMed1994

Regulation of early flowering in Pinus banksiana.

Seedlings of three families of jack pine (Pinus banksiana Lamb.) were subjected to 16 combinations of photoperiod, growth environment (outdoors, greenhouse and biotron) and gibberellin (GA(4/7)) treatment. After 14 months, which included two dormancy induction periods, ovulate flowering was observed. There was a strong positive correlation between flowering and seedling height; female flower production was stimulated by both a declining photoperiod during bud development and GA(4/7) treatment; and there was an interaction between GA(4/7) treatment and family, such that the difference in flowering intensity between a late-flowering and an early-flowering family was eliminated by GA(4/7) treatment. The results suggest that the genetic control over the time of onset of flowering, and GA(4/7)-induction of flowering depend on a common mechanism.

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PubMed1994

Aftereffects of maternal environment on autumn frost hardiness in Pinus sylvestris seedlings in relation to cultivation techniques.

Full-sib families of Pinus sylvestris (L.) from genetically identical parent clones, grown at three geographic locations (64, 59.5, and 56 degrees N), were tested for autumn frost hardiness. At one of the locations (64 degrees N), maternal clones were grown in plots subjected to different site treatments. Progenies raised in a heated greenhouse with additional artificial light were induced to undergo two shoot elongation periods, separated by a period with long nights and non-hardening temperatures, followed by a hardening period. Frost hardiness was tested by exposing seedlings to -17, -19, or -21 degrees C during the hardening period. Progenies produced at the northernmost locality (64 degrees N) were the most hardy. The hardiness ranking among localities and the magnitude of differences in hardiness were in accordance with earlier results obtained from the same crosses that had undergone only one shoot elongation period. Effects of maternal site treatments were significant but small compared with family differences. The growth regimes used in the present study did not eliminate maternal effects induced by geographic location, but maternal effects related to site treatment decreased substantially in relation to family variation when compared with seedlings that had undergone only a single shoot elongation period. The results are discussed in relation to other studies of the same crosses raised under different growth conditions.

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PubMed1994

Effects of maternal environment on mortality and growth in young Pinus sylvestris in field trials.

The same full-sib families of Scots pine (Pinus sylvestris L.) were created by artificial pollination of genetically identical grafts at three localities in Sweden at approximately 56, 59 and 64 degrees N. Two field trials were established with one-year-old plants in different years at latitude 64 degrees N. Height and survival were monitored for 4-5 years following planting. Maternal environment had significant aftereffects on the height of progeny. In both field trials, plants with the maternal parent at 59 degrees N were tallest and plants with the maternal parent at 64 degrees N were shortest. The aftereffects of maternal environment were as large in six-year-old plants as in one-year-old plants. In one field trial, maternal environment had a significant effect on mortality six years after germination but not after three years. Mortality increased with decreasing latitude of the maternal location. We conclude that the aftereffects of maternal environment are too large and too permanent to be regarded as unimportant.

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PubMed1994

Photosynthesis, water relations, and growth of planted Pinus strobus L. on burned sites in the southern Appalachians.

We measured net photosynthesis, leaf conductance, xylem water potential, and growth of Pinus strobus L. seedlings two years after planting on two clear-cut and burned sites in the southern Appalachians. Multiple regression analysis was used to relate seedling net photosynthesis to vapor pressure deficit, seedling crown temperature, photosynthetically active radiation (PAR), needle N, xylem water potential, and soil water, and to relate seedling size and growth to physiological measurements (average net photosynthesis, leaf conductance, and cumulative xylem water potential), soil water, needle N, seedling temperature, and PAR. Seedling net photosynthesis was significantly related to vapor pressure deficit, midday water potential, crown temperature, and PAR (r(2) = 0.70) early in the growing season (May 1992) with vapor pressure deficit alone explaining 42% of the variation. As neighboring vegetation developed, light became more limiting and significantly reduced seedling net photosynthesis later in the growing season (July, August, and September). Final seedling diameter was significantly related to competitor biomass, average photosynthetic rate, and needle N (r(2) = 0.68).

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PubMed1994

Movement of respiratory CO(2) in stems of loblolly pine (Pinus taeda L.) seedlings.

Temperature-independent fluctuations in stem CO(2) efflux were measured in Pinus taeda L. seedlings. Stem CO(2) efflux was measured during high and low transpiration rates, high and low net photosynthesis rates, and normal and interrupted substrate supply conditions. Stem CO(2) efflux rates were an average of 6.7% lower during periods of high transpiration compared to periods of low transpiration. This difference in stem CO(2) efflux rates was not due to water stress. The most likely cause was movement of respiratory CO(2) in the transpiration stream. Interruption of substrate supply to the stem by phloem girdling reduced stem CO(2) efflux rates. Increasing net photosynthesis rates from low to high had no effect on stem CO(2) efflux, but decreasing net photosynthesis from high to low caused relatively small reductions in stem CO(2) efflux. These results indicate that diurnal changes in net photosynthesis rate may play a small role in temperature-independent afternoon depressions of stem CO(2) efflux. The transport of respiratory CO(2) by the transpiration stream compromises measurements of woody tissue respiration obtained by commonly accepted gas exchange techniques. This phenomenon could also affect measurement of leaf net photosynthesis and branch woody tissue respiration.

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PubMed1994

Changes in protein synthesis during drought conditioning in roots of jack pine seedlings (Pinus banksiana Lamb.).

The impact of drought conditioning on the ability of eight-week-old jack pine (Pinus banksiana Lamb.) seedlings to withstand drought was assessed. Two progressive cycles of drought conditioning significantly increased the survival of seedlings subjected to a subsequent prolonged drought. The in vivo accumulation of several root membrane proteins during drought conditioning was correlated with an increase in seedling survival. A group of root proteins, ranging in molecular mass from 43 to 47 kDa, increased accumulation during one cycle of drought conditioning and to a lesser extent during two cycles of drought conditioning. The accumulation of several low molecular mass membrane and soluble proteins also increased during drought conditioning, suggesting that these proteins may play an important role in the enhancement of drought tolerance. In vitro translation studies showed a general increase in the abundance of protein products encoded by mRNAs from drought-conditioned seedlings. Although the majority of the in vitro translation products appeared in both control and drought-conditioned seedlings, one mRNA encoding a 15 kDA translated protein was more prominent during the second cycle of drought conditioning.

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PubMedDate not supplied

Seasonal development of leaf area in a young, widely spaced Pinus radiata D. Don stand.

Measurements of needle elongation and needle death were made at two-week intervals during a year on 250 branch units spread throughout the crowns of six trees (three high-pruned, three low-pruned) in a widely spaced, 6- to 7-year-old Pinus radiata D. Don plantation in New Zealand. The trees were well supplied with nutrients and water. During the year, mean tree height increased by 1.2 m and the cross-sectional area of stem below the green crown (used to predict leaf area) for the average tree increased from 8.7 x 10(3) to 13.9 x 10(3) mm(2). The increase in stem cross-sectional area occurred throughout the year except for two months in early winter (May and June). Elongation of Age 0 needles began in Spring (October), continued through summer, and the mean date for 95% completion of elongation was in autumn (early May), approximately 200 days after elongation began. Mean maximum needle length in the canopy decreased with increasing branch order and was 136 and 94 mm for Order 1 and Order 3 units, respectively. Needle elongation was related to thermal time, using growing degree days with a base temperature of 6 degrees C. The mean maximum rate of needle elongation in the canopy was 0.11 m ( degrees C day)(-1) and this occurred in early summer (mid-December), 47 days after elogation started. Maximum needle length and the rate of elongation increased, and the time taken to reach 95% elongation decreased with increasing height in the canopy. A smaller autumn flush of needles started in summer (January) and the needles elongated linearly at a mean rate of 0.07 mm ( degrees C day)(-1) until the end of the growing season when temperatures fell below the base value. At the end of the year, the mean length of needles from the autumn flush was 66 mm. The density of needles did not change with height in the canopy and there were no significant changes seasonally. The mean density values for Age 1 and Age 0 needles were 336 and 286 kg m(-3), respectively. Dry weight per unit length did not change seasonally for Age 1 needles, but the mean values for Order 1 and Order 2 needles were 0.32 and 0.23 mg mm(-1), respectively. Dry weight per unit length for Age 0 needles increased during the growing season (October to February). This was particularly apparent for Order 1 needles where the mean value increased from 0.12 to 0.25 mg mm(-1). Death of Age 1 needles started in midsummer (mean date was January 24) which coincided with the time of maximum elongation of Age 0 needles, but there were differences in timing among individual trees. The mean rate of death was 1.7% day(-1) and the mean duration was 59 days. Leaf area index for the stand increased from 3.2 to 5.3 (all-surfaces basis) during the year. At the end, 92% of the leaf area had grown during the year and 60% of it was on Order 2 branch units. The models for needle elongation and needle death were used to scale up to seasonal changes in canopy leaf area index. Leaf area index peaked with increasing Age 0 leaf area to 6.1 in summer (January), fell to 4.7 in March as Age 1 needles died, then increased slightly again. The seasonal dynamics are consistent with the hypothesis of Cannell (1989) that the timing of maximum leaf area index within a year is optimal for maximizing biomass production.

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PubMedDate not supplied

Offsetting changes in biomass allocation and photosynthesis in ponderosa pine (Pinus ponderosa) in response to climate change.

We examined the effect of climate on aboveground biomass allocation of ponderosa pine (Pinus ponderosa) by measuring trees in disjunct forest stands growing on the same substrate at high-elevation montane sites and low-elevation desert sites. Climatic differences between the sites were comparable to the difference between present and future climates of interior North America that is expected to result from a doubling of atmospheric CO(2) concentration. Relative to the montane populations, the desert populations allocated a greater proportion of biomass to sapwood (functional xylem) at the expense of foliage. The leaf/sapwood area ratio and percent of aboveground biomass in sapwood for trees of the same height were 0.201 m(2) cm(-2) and 58% for montane trees and 0.104 m(2) cm(-2) and 71% for desert trees. In a phytotron experiment, increases in net photosynthesis and net assimilation rate for seedlings grown under future conditions of high CO(2) and temperature were offset by a decrease in leaf area ratio. As was observed for large trees at different elevations, increased temperatures caused an increase in biomass allocation to stem in the phytotron seedlings. Thus, CO(2)- and temperature-driven shifts in biomass allocation negated the effect on growth of the CO(2)-driven increase in carbon assimilation rate. Our data from the controlled growth chamber and field experiments suggest that future climate conditions, including elevated atmospheric CO(2), may not stimulate growth and productivity of ponderosa pine.

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PubMed1995

Dynamic response of stomata to changing irradiance in loblolly pine (Pinus taeda L.).

Dynamic changes in stomatal conductance and the rate of photosynthesis were measured as periods of shading (decrease in irradiance from 800 to 200 micro mol m(-2) s(-1)) between 5 and 60 min were imposed on needles of Pinus taeda L. trees under laboratory conditions. Shading induced a 39% decrease in stomatal conductance but the rate of change was slow. Average time constants (+/- standard error) were shorter for the decrease in stomatal conductance when shading was imposed for 30 min (14.8 +/- 1.3 min) than for the increase in stomatal conductance when shading was removed (25.5 +/- 3.4 min). The time constants for increasing stomatal conductance when shading was removed were linearly related to the length of the previous dark period. The rate of photosynthesis fell immediately by 58% when shading was imposed and increased more rapidly than the change in stomatal conductance when shading was removed. The increase in photosynthesis during the induction phase after shading was removed was limited by both stomatal and biochemical effects. The long time constants for stomatal response contributed to the poor correlations between stomatal conductance and instantaneous measurements of irradiance from field data. However, the slow response of stomatal conductance to changes in irradiance had little effect on total daily transpiration, carbon gain and water-use efficiency.

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PubMedDate not supplied

Abscisic acid and zygotic embryogenesis in Pinus taeda.

Indirect ELISA was used to quantify (+)-abscisic acid (ABA) in developing zygotic embryo and megagametophyte tissues from two loblolly pine (Pinus taeda L.) mother trees. On a dry weight basis, embryonic and megagametophytic ABA concentrations were highest during early development and decreased steadily to their lowest values at cone ripening. Embryonic ABA concentration was significantly higher than megagametophytic ABA concentration. The ABA content of embryos was lowest during early to mid-development; it increased rapidly during mid-development, subsequently declined, and then either remained constant or declined at cone ripening (late development). Total ABA per embryo increased rapidly just before the rapid increase in embryo dry weight. Total ABA per megagametophyte remained constant throughout development, except during mid-development when it temporarily declined.

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PubMedDate not supplied

Effects of supplemental mass pollination (SMP) in a young and a mature seed orchard of Pinus sylvestris.

The effects of supplemental mass pollination (SMP) were studied in two Pinus sylvestris seed orchards differing in pollen production. Pollen was dusted over the whole tree during the period of peak female receptivity using a pressurized backpack sprayer. The success of SMP was assessed by means of allozyme markers. In the orchard with high pollen production, detectable differences in SMP success rate were found between clones, but the success rate was not influenced by the number of pollinations per day. The average estimated success rate of SMP was 19%. In the orchard with low pollen production, no significant differences in SMP success rate were found between years (22 versus 34%) or between clones. The SMP success rate in the low pollen production orchard varied between 14 and 69%.

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PubMed1995

Growth and water relations of three geographically separate origins of maritime pine (Pinus pinaster) under saline conditions.

Water relations and growth of maritime pine (Pinus pinaster Ait.) were investigated in 2-year-old seedlings of French ('Landes'), Iberian ('Iberian') and Moroccan ('Tamjoute') origin raised for 67 days in a flowing solution culture system containing 0, 50, 150 or 250 mM NaCl. Height growth, and stem, needle and root dry matter were reduced by salinity with minor differences among geographic origins. Predawn needle water potential was decreased by salinity and corresponded approximately to the osmotic potential of the nutrient solution. Stomatal conductance was reduced according to the amount of salinity applied. Whole-plant hydraulic conductance was also reduced, even when expressed on a root dry weight basis. The osmotic potential of xylem sap was five- to sixfold lower than that of the nutrient solution. Seedlings of the most southerly origin (Tamjoute) exhibited a greater ability to decrease osmotic potential under saline conditions than seedlings of more northerly origin (Landes and Iberian) as a result of higher mineral cation transport to the shoot.

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PubMedDate not supplied

Stem maintenance and construction respiration in Pinus ponderosa grown in different concentrations of atmospheric CO(2).

To determine whether long-term growth in enriched CO(2) atmospheres changes the woody tissue respiration component of aboveground carbon budgets, we measured woody tissue respiration of stems of 3-year-old ponderosa pine (Pinus ponderosa Laws.) grown in ambient (350 ppm) or twice ambient (700 ppm) atmospheric CO(2) concentrations in open-top field chambers located in Placerville, CA. Total respiration rate was measured by gas exchange, and construction respiration was calculated from the construction cost, percent carbon of stem samples and relative growth rate. Maintenance respiration was determined as the difference between total and construction respiration. The Q(10) of respiration was greater in stems grown in elevated CO(2) than in stems grown in ambient CO(2) (2.20 versus 1.67). As a result, mean daily respiration per unit volume of wood modeled for the month of September was greater in trees growing in elevated CO(2) than in ambient CO(2) (46.75 versus 40.45 mol m(-3) day(-1)). These effects of atmospheric CO(2) concentration were not the result of differences in relative growth rate. Calorimetric analyses of woody tissue construction cost indicated no difference between treatments; however, trees in the elevated CO(2) treatment showed a 1% lower carbon concentration than trees in the ambient CO(2) treatment. Estimates of construction respiration did not differ between treatments, confirming that the treatment differences in mean daily respiration rate were attributable to the maintenance component. Under future predicted atmospheric conditions, changes in the maintenance respiration of woody tissue may lead to an increase in the respiration component of whole-plant carbon budgets of ponderosa pine. Our results suggest that potential increases in the maintenance component of stem respiration should be considered when modeling the response of forest stand growth to enriched CO(2) atmospheres.

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PubMedDate not supplied

Carbon partitioning in Pinus radiata stands in relation to foliage nitrogen status.

First rotation Pinus radiata D. Don trees were grown on a nitrogen-deficient sand dune in an experimental design that included lupin (Lupinus arboreus Sims) as an understory species, and biennial application of balanced fertilizer in a replicated split-plot factorial design with thinning treatments as subplots. From an initial 2222 stems ha(-1), stands were thinned to 1483 and 741 trees ha(-1) at ages 2 and 4 years, respectively. Mean annual production of foliage, branches, stem, coarse roots, and cones was estimated from measurements of the dry matter content at ages 7, 10, 11 and 17 years. A model was used to estimate total above- and belowground dry matter production from measurements of leaf area index and foliar nitrogen concentration. An estimate of fine root production was obtained from the difference between the model estimate of total production and the estimate of aboveground production. The fertilizer and lupin treatments increased foliage nitrogen concentration, leaf area index and dry matter production of most aboveground components. In unthinned stands, foliage production ranged from 3 to 6 Mg ha(-1) year(-1), branch production from 1 to 4 Mg ha(-1) year(-1), and stem production from 8 to 19 Mg ha(-1) year(-1), depending on site fertility. Partitioning of aboveground production to foliage, branches, stems, and cones changed with tree age but it was not significantly influenced by the treatments. The fractions of aboveground dry matter production partitioned to foliage, branches, stems and cones were 0.23, 0.12, 0.63 and 0.02, respectively, for trees between ages 7 and 11 years, and 0.21, 0.08, 0.67 and 0.04, respectively, for trees between ages 11 and 17 years. With increasing foliage nitrogen concentration, partitioning to branches increased significantly, whereas partitioning to stems decreased. The fraction of total dry matter production partitioned to stems decreased significantly with thinning from 0.40 to 0.27 with a concomitant increase in the fraction partitioned to fine roots from 0.31 to 0.46. The average fraction partitioned to fine roots was 0.46 and 0.30 in unfertilized and fertilized stands, respectively. Stem production was more highly correlated with fine root partitioning than with leaf area index. Fine root production was not significantly affected by fertilizer application. The ratio of total net primary production to leaf area index increased significantly with thinning, but not with site fertility or stand age. The ratio of aboveground dry matter production to leaf area index increased with stand age and with the application of fertilizer but not with thinning.

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