Southern Provenances Research Articles

Cold Hardiness of the Rare Dirca occidentalis: Comparisons to Dirca palustris from Disparate Provenances

Abstract We determined the cold hardiness of Dirca occidentalis (western leatherwood) within its restricted natural distribution in northern California and made comparisons to Dirca palustris (eastern leatherwood) from northern (Iowa) and southern (Florida) provenances. Stems of western leatherwood were sampled twice while all or some plants were dormant (October 27 and December 8, 2004, respectively) and again on January 19, 2005, when flowering and incipient vegetative shoot growth of most plants had begun. Stems of D. palustris were sampled on the same schedule and on March 2, 2005 (Iowa and Florida) and April 13, 2005 (Iowa) such that the last sampling date coincided with flowering and incipient vegetative shoot growth. Lowest survival temperature was determined based on visual assessments of the viability of cambium and phloem of stems exposed to progressively lower temperatures in a freezer. Lowest survival temperature of western leatherwood was −6 to −3C (21 to 27F) regardless of date. Eastern leatherwood accrued hardiness through mid-winter and then deacclimated; minimal lowest survival temperature of eastern leatherwood was −33C (−27F) in Iowa and −17C (1F) in Florida. The minimal cold hardiness of western leatherwood is consistent with its natural distribution in specialized niches within a Mediterranean climate. Unless western leatherwood accrues increased hardiness when planted where winters are harsh, its horticultural use will be restricted to areas with mild winters. In contrast, widespread use of eastern leatherwood is feasible if production challenges are resolved and selections from climatically appropriate provenances are used.

Elevate concentrazioni di ozono nell’Italia mediterranea: una sfida alle foreste?

Abstract: Tropospheric ozone pollution has changed from local phenomenon to global issue, because of a continuous rising - especially in developing countries - and intercontinental transport. Ozone ground levels, however, are higher in the world regions with strong photochemical activity, like the Mediterranean basin. The aim of this work is to review available data on ozone ground levels and damages to forests in Italy, with focus on the areas exposed to the highest concentrations, i.e. Southern Italy. Data from both ozone monitors and passive samplers suggest that ozone levels increase North to South in Italy. Therefore, an increase in ozone damages to forests is likely across this gradient. Conversely, the reports (presence/absence) of visible ozone-like foliar injury do not show a clear geographic trend, although they are still limited in number. Preliminary investigations suggest that ozone tolerance in evergreen sclerophylls and Southern provenances is higher than in mesophilic species and Northern provenances. The higher tolerance is due both to avoidance, i.e. stomatal closure, and to an active antioxidant pool. This would suggest AOT40 is modified on the basis of both stomatal conductance and antioxidant capacity. Available data are still not enough to determine the effect of present ozone regimes on Italian Mediterranean forests. Future investigations should aim at: (1) filling the gap on ozone levels in Italian remote areas, by using passive samplers and/or biomonitoring; (2) establishing ozone responses in the most typical Italian vegetation, for both O3 uptake and detoxification, in realistic conditions and in interactions with other factors, mainly drought and the increase in atmospheric CO2 concentrations; (3) extensive monitoring and quantification of ozone-like foliar injury across Italy. Confirmation of higher ozone tolerance in the Mediterranean vegetation might imply differing ozone critical levels across Europe.

Nordic provenance trials with Abies lasiocarpa and Abies lasiocarpa var. arizonica: three-year results

In three Nordic field trials, 26 provenances of Abies lasiocarpa (Hook.) Nutt. and Abies lasiocarpa var. arizonica (Merriam) Lemmon were evaluated 3 yrs after establishment. The focus was on 16 traits important for adaptation, establishment and production of Christmas trees. For all three sites in Denmark, Norway and Iceland, survival ranged from 89 to 96%. Provenances showed statistically significant differences for all but two traits. For all traits there was significant interaction between provenance and site. Analysis of ecovalens showed that for most traits, only a limited number of provenances contributed substantially to the interaction. Therefore, a large proportion of the provenances showed a fairly consistent ranking across sites. The frequency of potential Christmas trees in the provenances ranged from 10 to 49%. Southern provenances from New Mexico and Arizona seemed to have the best potential for producing high-quality Christmas trees. The southern provenances added substantially to the interaction between provenance and site for budset, lammas growth and colour. When using multivariate statistical methods on all measured traits, the provenance clusters fitted neatly into six distinct geographical regions.

Genetic variability in a narrow endemic snapdragon (Antirrhinum subbaeticum, Scrophulariaceae) using RAPD markers.

Antirrhinum subbaeticum is an endangered species inhabiting fragmented limestone cliffs. In the last 3 years, a drastic population decline has been observed in three of four known populations and the estimated number of surviving individuals is now close to 400. A RAPD study was conducted to evaluate the levels of genetic variation present in this species to improve conservation guidelines. Thirty-nine polymorphic products identified 66.1% of the samples by unique RAPD multilocus profiles. A cluster analysis grouped the samples into two broad groups corresponding to northern or southern provenances. AMOVA analysis showed that only 17.7% of the genetic diversity was partitioned within populations. These results are in contrast to data available for other Antirrhinum species. This genetic structure could be explained by the predominant selfing behaviour exhibited by A. subbaeticum as opposed to the allogamy of other congeners. Genetic diversity within populations does not seem to be strongly related to population size and historical factors could be responsible for the very low levels of genetic diversity found in one population. Given the low genetic diversity within populations, it is suggested that an extensive sampling of individuals be made for recovering appropriate levels of the gene pool for ex situ preservation. However, translocation of individuals to the genetically weakened Bogarra population from other sources is not recommended.

Relative susceptibility of northern and southern provenances of Pinus greggii to infection by Sphaeropsis sapinea

Sphaeropsis sapinea is a well-known pathogen of Pinus spp. that causes severe die-back, in South Africa. In this study, 65 families representing both the northern and southern populations of P. greggii were evaluated for their tolerance to infection and subsequent die-back caused by S. sapinea. Families were evaluated for tolerance following natural infection after hail damage, as well as through inoculation. Variation in tolerance of trees after natural infections, occurred amongst families of both the northern and southern provenances, but highly significant differences in tolerance were observed between the two provenances. P. greggii trees of the southern provenances were significantly more susceptible to natural infection after hail damage. Artificial infection was not suitable for prediction of susceptibility to natural infection after hail damage. These observations have significant practical implications for plantation establishment in South Africa.

Phenology and diameter increment in seedlings of European beech ( Fagus sylvatica L.) as affected by different soil water contents: variation between and within provenances

The effect of different soil water levels on phenology and growth of 14 provenances of European beech ( Fagus sylvatica L.) was investigated in a glasshouse experiment. The genetic variation within one provenance was further studied by including 10 half-sib families from a Danish stand in the experiment. Flushing and the time for onset of diameter growth were significantly different between provenances. Length of the growing season varied significantly among provenances and was highly affected by the soil water content. Root collar diameter increment during the experimental treatment was reduced by 43% in plants at low compared to plants at medium and high soil water content. The corresponding reduction in height was 53%. Differences between provenances and the interaction between provenances and the soil water treatments were significant for growth response. This interaction term was not significant in the material of 10 half-sib families. Linear geographic and clinal trends were revealed for growth and phenological parameters, but these relationships depended on the soil water levels. The provenances from northern Europe had a fairly homeostatic expression on a low growth level across the soil water gradient, whereas the southern provenances showed a much stronger positive response to increase in soil water content. Consequently, the south European provenances had a greater adaptability to the changing growth conditions. The genetic variation in growth response within one Danish provenance was comparable with the variation between provenance under dry soil conditions, whereas this was not the case under moist and wet soil conditions. The results indicate that a substantial gain in evolutionary adaptability is possible for north European forestry by choice of material from central and southern Europe or by mixing autochton plant material with more southern seed sources.

Heat Tolerance of Selected Provenances of Atlantic White Cedar

Seedlings of six provenances of Atlantic white cedar [Chamaecyparis thyoides (L.) B.S.P.] (Escambia Co., Ala., Santa Rosa Co., Fla., Wayne Co., N.C., Burlington Co., N.J., New London Co., Conn., and Barnstable Co., Mass.) were grown in controlled-environment chambers for 12 weeks under 16-hour photoperiods with 16-hour days/8-hour nights of 22/18 °C, 26/22 °C, 30/26 °C, 34/30 °C or 38/34 °C. Considerable variation in height, foliage color, and overall plant size was observed among plants from the various provenances. Seedlings from the two most northern provenances (Massachusetts and Connecticut) were most heat sensitive as indicated by decreasing growth rates at temperature regimes >22/18 °C. In contrast, plants from New Jersey and the three southern provenances (North Carolina, Florida, and Alabama) exhibited greater heat tolerance as indicated by steady or increasing growth rates and greater top and root dry weights as temperature regimes increased above 22/18 °C. Growth rates of seedlings from the four aforementioned provenances decreased rapidly at temperature regimes >30/26 °C suggesting low species tolerance to high temperatures. There were no significant differences in seedling dry matter production among provenances when temperature regimes were ≥34/30 °C. Net shoot photosynthesis and dark respiration of plants did not vary by provenance; however, net photosynthesis was temperature sensitive and decreased at temperature regimes >26/22 °C. Foliar respiration rates increased as temperature increased from 22/18 °C to 26/22 °C, but then remained relatively constant or decreased at higher temperature regimes. Plants at temperatures ≥34/30 °C exhibited severe stunting, chlorosis, and necrosis on branch tips. However, tissue concentrations of N, P, K, Ca, Mg, Fe, Zn, Cu, and Mn generally increased with temperature regimes >30/26 °C indicating that mineral nutrient concentration was not a limiting factor at high temperatures.

Provenance variation in morphology and leaflet anatomy of Parkia biglobosa and its relation to drought tolerance

Measurements of morphological and anatomical characteristics made on 4-month-old seedlings from five provenances of Parkia biglobosa (Jacq.) Benth., grown in a tropical greenhouse under controlled conditions, showed significant differences between the northern provenances, which represented the Sudan savanna zone, and the southern provenances which represented the forest zone of the species distribution. Seedlings of provenances from the savanna zone showed more xerophytic characteristics than those from the forest zone. They were smaller in height, with a greater number of smaller leaflets per pinnae, a lower specific leaflet mass, smaller palisade and guard cells and a lower ratio of palisade:non-palisade tissue. There were also significant differences in the same characteristics, except palisade cell length, between provenances from the easterly and westerly extremes of the species range. Stomatal conductance measured after 2 weeks of droughting also showed that provenances from the savanna zone had higher values, indicating greater physiological activity and reduced stress, compared with provenances from the forest zone. Multivariate discriminant analysis of the morphological and anatomical characteristics showed that 98% of the seedlings were classified correctly with respect to provenance. The squared distances between provenances were closely related to the geographical distances between locations. Yet, not all variation in leaf anatomy could be explained by the difference in climatic conditions from north to south. Also drought tolerance was not always related to morphological and anatomical features. It is possible that clinal variation within the species from east to west may be interacting with climatic differences from north to south.

Seasonal variation in the frost hardiness of Scots pine and Norway spruce in old provenance experiments in Finland

Temperature is one of the major factors regulating the acclimation of forest trees to winter conditions in the boreal zone. The projected climate warming may therefore affect the overwintering pattern of trees. In this study, old provenance trials with Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst) were used to simulate the effects of a warmer climate on the seasonal variation in frost hardiness. In both species, there were differences between northern and southern provenances in the timing of bud and needle hardening during autumn. The northern provenances hardened earlier. During the dehardening phase in spring, no significant difference was found between the provenances. For buds of Norway spruce, fluctuations in hardiness that coincided rather well with fluctuations in the ambient temperature were observed during mid-winter. The results of this study do not support the theory that climate warming will increase the risk of frost damage in Scots pine and Norway spruce in boreal areas. Further research is recommended.

Heat Tolerance of Selected Provenances of Atlantic White Cedar

Uniform seedlings of six provenances (Escambia Co., Ala.; Santa Rosa Co., Fla.; Wayne Co., N.C.; Burlington Co., N.J.; New London Co., Conn.; and Barnstable Co., Mass.) of Atlantic white cedar [Chamaecyparis thyoides (L.) B. S. P.], were transplanted in Apr. 1997 into 0.95-L plastic containers with a medium of 1 peat: 1 perlite: 1 vermiculite (v/v). Plants were acclimatized at 26/22 °C under a 16-hr photoperiod for 2 weeks before treatment initiation. Fourteen seedlings per provenance were then transferred to each of five growth chambers maintained at 16/8 hr thermoperiods of 22/18 °C, 26/22 °C, 30/26 °C, 34/30 °C, or 38 /34 °C with a 16-hr photoperiod of 550–600 μmolμm–2μs–1. Seedlings were arranged in a split-plot design with a 5 × 6 factorial arrangement of treatments (5 temperatures × 6 provenances). Plants were harvested 12 weeks after treatment initiation and data recorded. Temperature had a significant effect on overall growth with responses to temperature varying according to provenance. There was a highly significant (P ≤ 0.0001) temperature × provenance interaction for height, stem caliper (measured below the lowest leaf), and foliar, stem, root, and shoot (foliar dry weight + stem dry weight) dry weights. Top and root dry weights were maximized for the northern provenances (Connecticut and Massachusetts) at 22/18 °C. At 26/22 °C and 30/26 °C, the northern provenances (Connecticut and Massachusetts) had the lowest top and root dry weights. However, the southern provenances (Alabama, Florida, and North Carolina) had the greatest top dry weights at 26/22 °C. At 30/26 °C, the southern provenances (Alabama and Florida) and the New Jersey provenance had the greatest top dry weights but they were not significantly different from 26/22 °C. Root dry weights were not significantly different between 26/22 °C and 30/26 °C for the Alabama and New Jersey provenances, but were significantly different for the North Carolina and Florida provenances. Regardless of provenance, dramatic reductions occurred for all growth measurements when temperatures exceeded 30/26 °C. For top and root dry weights, there were no significant differences among the six provenances at 34/30 °C and 38/34 °C. All plants at the highest temperatures of 38/34 °C did not survive by week 8.

Influence of Stratification, Temperature, and Light on Seed Germination of Selected Provenances of Atlantic White Cedar

Cones of six provenances (Escambia Co., Ala., Santa Rosa Co., Fla., Wayne Co., N.C., Burlington Co., N.J., New London Co., Conn., and Barnstable Co., Mass.) of Atlantic white cedar [Chamaecyparis thyoides (L.) B. S. P.], were collected Fall 1994 (Alabama, North Carolina, New Jersey, and Connecticut), Winter 1995 (Massachusetts), or Fall 1995 (Florida). Cones were dried for 2 months, followed by seed extraction and storage at 4°C. Seeds were then graded and stratified (moist-prechilled) for 0, 30, 60, or 90 days. Following stratification, seeds were placed at 25°C or an 8/16-hr thermoperiod of 30°/20°C with daily photoperiods of 0, 1, or 24 hr. Germination was recorded every 3 days for 30 days. Temperature, stratification, and light had significant effects on germination. However, responses to these factors varied according to provenance. Averaged over all treatments, the Alabama provenance exhibited the greatest germination (61%), followed by the Florida provenance (45%), with the remaining provenances ranging from 20% to 38%. However, there were specific treatments for each provenance that resulted in germination > 50%. The three southern provenances (Alabama, Florida, and North Carolina) required 30 days of stratification for maximum germination. They did not exhibit an obligate light requirement, but photoperiods ≥ 1 hr increased germination greatly over seeds in darkness. In contrast, the northern provenances (New Jersey, Connecticut, and Massachusetts) had an obligate light requirement. These provenances only required 30 days stratification with continuous light for maximum germination. When subjected to a 1-hr photoperiod, seeds from the northern provenances required longer durations of stratification for maximum germination. Regardless of the length of stratification, the New Jersey provenance required a 24-hr photoperiod to maximize germination. When averaged over all treatments, total germination for each provenance was greater at 30°/20°C than 25°C (43% vs. 31%).

Genetic variation in seed and seedling traits in 12 African provenances of Faidherbia albida (del.) A. Chev. at Lodwar, Kenya

The extent of genetic variation in seed length, width, thickness, weight and germination percentage and seedling traits among and within 12 African provenances of Faidherbia albida was examined. The regional provenances showed a consistent variation in seed length, seed width and seed weight: the southern African provenances had the largest seeds and west African provenances the smallest. Seedling height, stem collar diameter and true leaf number differed (P = 0.05) among the provenances 90 days after germination. The seedlings from west Africa were shorter, had smaller stem collar diameter and fewer leaves. In contrast, the southern and east African provenances had taller seedlings with bigger seedling diameter and more leaves per seedling. Seedling traits did not show clear-cut divisions between southern and east African provenances, but the west African provenances formed a distinct group. Positive correlations were found in some of the seed characteristics and seedling height among provenances, which could be an important criterion for early provenance selection. Greater variation was observed for seed and seedling traits among than within provenances suggesting that selection among provenances might result in rapid genetic gain for the traits studied.

Comparing stem respiration and growth of jack pine provenances from northern and southern locations.

Stem respiration rates of 31-year-old jack pine (Pinus banksiana Lamb.) trees from northern and southern provenances growing in a common garden were compared. At 15 degrees C, the seasonal course of stem respiration rate of northern provenances was not statistically different from that of southern provenances. A relationship existed between maintenance respiration rate and stem growth rate. Because relationships between sapwood relative growth rate and annual growth and maintenance respiration rates were similar for northern and southern provenances, no clinal differences in stem respiration rates were observed.

Root-zone Stress Effects on Water Relations and Growth of Silver, Red, and Freeman Maples

Freeman maples (Acer ×freemanii E. Murray) are suspected to be more resistant to environmental stress than red maples (A. rubrum L.) because the lineage of Freeman maple includes silver maple (A. saccharinum L.). Little is known, however, about stress resistance of silver maple, and few data from direct comparisons of red and Freeman maples are available. Our objectives were to determine effects of root-zone heat on silver maples from northern and southern provenances, and to compare red and Freeman maple cultivars for resistance to rootzone heat stress and drought. There were no provenance-by-temperature interactions when silver maples from 33.3°N (Mississippi) and 44.4°N (Minnesota) latitude were grown with root zones at 29 and 35°C. Plants from 44.4°N latitude had 36% higher fresh mass, 43% more leaf surface area, and 35% and 59% higher, respectively, root and shoot dry masses than plants from 33.3°N latitude. Midday xylem water potential was 68% more negative for plants at 35°C than for plants at 29°C, and transpiration rate was 129% less for plants with root zones at 35°C than for those with root zones at 29°C. During preliminary work with Autumn Flame and Franksred red maple and Indian Summer and Jeffersred Freeman maples, rooted cuttings were grown in 25 and 37°C root zones under both drought and nondrought conditions. Reductions in growth at 37°C were similar for all cultivars. Results of this work could influence development, marketing, and use of Freeman maples.

Three-year survival and growth of provenances of Pinus greggii in the tropics and subtropics

Eleven provenance/progeny tests of Pinus greggii Engelm. were assessed for survival and height at 3 years of age in Brazil, Colombia and South Africa. Trees of P. greggii from sources in northern Mexico (≈ 25°N latitude) were less than half as tall as trees from provenances in central Mexico (≈ 21°N latitude) when established in warm climates of Brazil and Colombia, (4.2 m vs. 1.6 m, respectively). The differences in height growth diminished between southern and northern sources in more temperate climates in South Africa (2.9 m vs. 2.1 m, respectively). External morphological differences in foliage were also pronounced between trees of the two regions when grown as an exotic. Trees from northern sources had shorter, stiffer, needles of darker green color than those from southern provenances. The most promising of the southern provenances across all sites were El Madroño (Queretaro) and Laguna Seca (Hidalgo). La Tapona (Nuevo Leon) and Los Lirios (Coahuila) performed well among the northern sources. Pinus greggii should be tested where low rainfall and cold are considered limiting factors for good growth of P. patula.

Growth, shoot phenology and physiology of diverse seed sources of black spruce: I. Seedling responses to varied atmospheric CO(2) concentrations and photoperiods.

We conducted a greenhouse experiment to determine: (1) if diverse provenances of black spruce (Picea mariana (Mill.) B.S.P.) respond similarly in growth, phenology and physiology to an approximately 300 ppm increase in atmospheric CO(2) concentration, and (2) the influence of photoperiod on both provenance and provenance x CO(2) interaction effects. Seedlings from provenances that originated from the Yukon (63 degrees 34' N, 135 degrees 55' W), British Columbia (58 degrees 47' N, 123 degrees 38' W), Alberta (52 degrees 22' N, 115 degrees 15' W), Newfoundland (50 degrees 54' N, 56 degrees 06' W) and Ontario (48 degrees 59' N, 80 degrees 38' W and 45 degrees 10' N, 77 degrees 10' W) were subjected to growth analysis in greenhouse growth chambers supplied with 712 +/- 93 (SD) ppm CO(2) (elevated) or 394 +/- 59 ppm CO(2) (ambient). Seedlings from Provenances 7000 and 6901 were also subjected to an extended photoperiod treatment and periodically measured for shoot and root gas exchange. In response to a natural photoperiod, southern provenances grew more, broke and set bud later, and partitioned more biomass to shoot versus root than northern provenances. These differences among provenances were influenced by the extended photoperiod treatment but not by the elevated CO(2) treatment. Averaged across all provenances, elevated CO(2) increased seedling final weights by 55%; however, the elevated CO(2) treatment had no effect on the provenance differences in any measured trait. We conclude that the large differences in physiology, phenology and growth among these diverse provenances of black spruce were expressed similarly in both ambient and elevated atmospheric CO(2) concentrations.

Growth, shoot phenology and physiology of diverse seed sources of black spruce: II. 23-year-old field trees.

Four sources of 23-year-old black spruce (Picea mariana (Mill.) B.S.P.) from a provenance test at the Petawawa National Forestry Institute (46 degrees N, 77 degrees 30' W) were assessed for height growth, shoot phenology and seasonal gas exchange. The provenances were designated 7000 (Yukon, 63 degrees 34' N, 135 degrees 55' W), 6979 (Alberta 52 degrees 22' N, 115 degrees 15' W), 6908 (Ontario, 48 degrees 59' N, 80 degrees 38' W) and 6901 (Ontario, 45 degrees 10' N, 77 degrees 10' W). Trees of southern provenances (6901 and 6908) were considerably taller, and broke bud and ceased growth later than trees of northern provenances (6979 and 7000). In early spring, trees of northern provenances had higher net photosynthetic rates (P(n)) than trees of southern provenances (6908 and 6901). During midsummer, trees of Provenance 7000 generally had the highest P(n) as a result of low rates of shoot dark respiration (R(d)). Trees of northern provenances displayed an earlier autumn decline in P(n) than trees of southern provenances. Provenance differences in growth, shoot phenology and physiology agreed well with results from a greenhouse study of seedlings from the same provenances. We conclude that the poor growth performance of trees of northern provenances in Ontario was associated with: (1) a short period of shoot growth, (2) a high rate of dry matter partitioning to roots, (3) low rates of late-season P(n) in response to decreasing photoperiod, and possibly, (4) a high rate of root R(d).

Autumn frost damage: clonal variation in Sitka spruce

Current-year needles of Sitka spruce (Picea sitchensis) can be injured by frost after hardening of stem and buds in the autumn, and in Scotland trees of southern provenances are most susceptible to damage. In October 1993 a frost of -5°C caused needle damage to clonal plants of Alaskan, Queen Charlotte Islands, and Washington provenances of Sitka spruce that had been selected for variation in the onset of root dormancy. Visual damage assessment revealed significant differences among clones in the severity of damage, and this damage was positively correlated with the lateness of root dormancy. Measurement of electrolyte leakage from shoot samples confirmed the observed differences between clones. The large clonal differences in frost hardiness found in this study demonstrate a potential for selecting frost tolerant trees from within southern provenances of Sitka spruce.

Acid-rain-induced changes in cuticles and Ca distribution in Scots pine and Norway spruce seedlings

Seedlings of Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) were subjected to acid rain irrigation at pH 7, pH 4, and pH 3 three times a week during the growing seasons of 1986–1989 in a field experiment. Scanning and transmission electron microscopy, energy dispersive spectrometry, contact angle measurements, and chloroform extraction of waxes were used to detect physicochemical changes in the needle cuticles. The first detectable symptoms of acid rain were observed after 5 weeks of acid rain treatment at pH 3 and pH 4, which resulted in few CaSO4 crystallites on visibly undamaged pine and spruce needle surfaces. After 7 weeks of acid rain treatment there were CaSO4 crystallites scattered over the whole needle surface area and erosion of the epicuticular waxes could be observed occasionally. CaSO4 crystal formation later decreased, especially on the needles of seedlings treated at pH 3. Ca concentrations in the needles and roots of the seedlings and in the soil in the boxes were higher in the pH 3 treatments than elsewhere. The more abundant deposition of Ca oxalate crystallites on the inner walls of the epidermal and hypodermal cells of the spruce needles than on their outer walls was probably also connected with Ca leaching, caused by acid rain. Acid rain also delayed wax synthesis, as 2-month-old pine needles exposed to pH 3 and pH 4 had about 50% less wax than the water controls in early August. The needle surfaces of the southern provenances of spruce and pine seedlings were slightly less wettable after pH 4 treatment than after the control water treatment, because they probably benefited from N and S compounds in the irrigation water. The needle surfaces were more wettable in the pH 3 and water control seedlings than in the other treatments.

Branching Architecture of 3-year-old Plantation-grown Micropropagated Silver Maple

Whole-tree branch architecture was quantified by counting and measuring the lengths of main stems, basal branches, and all primary (1°), secondary (2°), and tertiary (3°) branches. Trees were grown in replicated clonal plantations established in 1991 on a southern Illinois lowland and an upland site. Fifty-two clones in each of five complete blocks were measured from each plantation. Number of primary branches that formed in 1991, 1992, and 1993, and the number of nodes in the terminal meter of growth were highly significant for silver maple provenance and for clones (four clones for each of 13 provenances), except that clonal differences were nonsignificant for the number of 1° branches on 1991 wood. There were significant effects of provenance and clone on total number and the various sizes of 2° and 3° branches. Generally, a greater number and longer length of 2° and 3° branches formed on trees from the more rapidly growing southern provenances.