Fall lifting and long-term freezer storage of ponderosa pine seedlings: effects on post-storage leaf water potential, stomatal conductance, and root growth potential

Post-storage water relations, stomatal conductance, and root growth potential were examined in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings from high- and low-elevation seed sources that had been lifted either in October or November and freezer stored, or in March, and then grown hydroponically in a greenhouse for 31 days. Seedlings lifted in October had poor root initiation (< 17 new roots per seedling), low predawn leaf water potentials (< -1.5 MPa), and low stomatal conductance (7.10 mmol m(-2) s(-1)) compared with seedlings lifted in November or March. There was little difference in post-storage water relations and stomatal conductance between seedlings lifted in November and those lifted in March. Throughout the 31-day test, seedlings from the high-elevation seed source produced 3-9 times more new roots, had higher predawn leaf water potentials (-0.6 to -0.7 MPa versus -1.1 to -1.6 MPa), and 1.3-5 times greater stomatal conductance than seedlings from the low-elevation seed source. For all seedlings on Day 31, the number of new roots was significantly related to predawn leaf water potential (r(2) = 0.65) and stomatal conductance (r(2) = 0.82). Similarly, the dry weight of new roots per seedling on Day 31 accounted for a significant amount of the variation in predawn leaf water potential (r(2) = 0.81) and stomatal conductance (r(2) = 0.49).     

Root wrenching and lifting date of slash pine: Effects on morphology,survival, and growth

Slash pine (Pinus elliottii Engelm.) seedlings were subjected to three wrenching treatments: One root wrenching in early August; Three root wrenchings in early August, September, and October; and No wrenchings. Seedlings were then lifted on five dates between November and February based on the number of chilling hours accumulated. All wrenched seedlings had reduced shoot dry weight, smaller shoot-root ratio, and smaller stem diameter and height. These morphological differences translated into improved survival as well as increased diameter and height growth when measured one and two years after planting. Only seedlings wrenched three times demonstrated improved root fibrosity. Furthermore, only multiple wrenched stock showed greater resistance to drying imposed prior to planting. At the time of lifting, seedlings lifted latest had greater stem diameter, increased root dry weight and number of root tips, and improved shoot-root ratio. However, no survival differences were detected across lifts, and those seedlings lifted earliest demonstrated the best height and diameter growth.This paper is Journal Series No. R00695 of the Institute of Food and Agricultural Sciences, University of Florida, Gainesville 32611.     

Slash pine bud dormancy as affected by lifting date and root wrenching in the nursery

Bud dormancy of root wrenched and unwrenched slash pine (Pinus elliottii Engelm.) seedlings growing in a forest nursery was measured on five lifting dates. Determination of bud dormancy was based on days to budbreak (DBB) under optimal growing conditions, mitotic activity in the apical meristem, chilling hours accumulated, and bud morphology. Based on DBB, seedlings were most dormant at Lift 2 on November 24 after exposure to 189 hours below 10 degrees C and 93 hours below 6.7 degrees C. Mitotic activity in the apical meristem was at its lowest 23 days later at Lift 3, possibly indicating the period when seedlings are most resistant to transplanting stresses. Multiple wrenching resulted in a slight shift in the dormancy cycle as wrenched seedlings set bud sooner in the nursery and broke bud sooner at the planting site in the spring than control seedlings. This implies that wrenched seedlings can be successfully lifted from the nursery earlier and will initiate spring shoot growth earlier than control seedlings.     

Bud development and dormancy in slash and loblolly pine. I. Speed of budbreak and second year height as related to lifting date

Slash and loblolly pine 1-0 seedlings were lifted from the nurserybed in late November, mid-December, late December, and mid-February. The buds of the seedlings were classified as set or growing two weeks prior to lifting and were re-examined upon lifting. For both species, buds that had set remained set whereas those that were classified as growing showed an decreasing trend of setting from November through December. A subset of seedlings was potted and maintained in a greenhouse to determine rate of budbreak; the remainder were field planted. In the greenhouse, loblolly pine broke bud fastest and slowest when lifted in mid-February and mid-December, respectively. The rate of slash pine budbreak increased over successive lifting dates. In the field, loblolly pine lifted in mid-December exhibited the highest percentage of growing seedlings; these seedlings were also tallest after one year in the field. Field-planted slash pine had the highest percentage of growing seedlings when lifted in late November. However, seedlings lifted in mid-December were tallest after one year.     

Effect of warm storage and date of lifting on the quality of Douglas-fir seedlings

The effect of warm storage (15 °C)for up to 21 days on the vitality of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings lifted on four occasions from October to January wasassessed using fine root electrolyte leakage (REL). After 0, 7 and 21 days warm storage, additionalseedlings were potted and placed in a controlledgreenhouse environment to determine root growthpotential (RGP) after 4 weeks and survival after 8weeks. REL was a poor indicator of survival potential;REL increased after 7 days storage, despite the factthat RGP and survival were unaffected. REL increased further during the remainder of the 21-days storage period, but values were often not greatly different from those following 7days storage. Storage for up to 21 days greatlydecreased RGP and survival. Seedlings lifted inOctober and November were most affected by storagetreatments, but differences among lifting dates wererelatively small.     

Effects of cold storage and water stress on water relations and gas exchange of white spruce (Picea glauca) seedlings

To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis.     

Orchard pollen contamination: joint estimation of realized levels on current growth and future effects on volume and value at rotation in coastal Douglas-fir in British Columbia

Pollen contamination was evaluated using control-pollinated seedlings pollinated with polymixes of orchard pollen and pure wildstand and wind-pollinated orchard seedlings. At age 7, seedlings pollinated with contaminate pollen were the shortest across all four sites, but had survival levels (83%) similar to open-pollinated (84%) and pure orchard seedlings (86%). Open-pollinated seedlings had intermediate heights while pure orchard seedlings were tallest. The level of pollen contamination in open-pollinated seedlots was estimated to be 26%. Survival for all pollen sources combined was similar at the two high-elevation sites (84%) and low-elevation sites (86%). Using a yield model to compare volume/ha at rotation age for open-pollinated orchard seedlings and pure orchard seedlings, differences were small and increased due to site index (SI; from 3 to 6?m³/ha) but not due to planting density. Equivalent discounted benefits at rotation were 27 vs. 54 C$/ha at the two extreme site indices (18 vs. 25), respectively. These projected reductions due to pollen contamination are magnified by the large area that is regenerated annually with orchard seed of coastal Douglas-fir and contamination can cause a reduction in benefits of up to C$748,500 per year at the highest SI at a planting density of 1111 trees/ha.     

Effects of planting time on pine weevil (Hylobius abietis) damage to Norway spruce seedlings

Feeding by pine weevil (Hylobius abietis L.) causes severe damage to newly planted conifer seedlings in most parts of Scandinavia. We investigated the effect of planting time and insecticide treatment on pine weevil damage and seedling growth. The main objective was to study if planting in early autumn on fresh clear-cuts would promote seedling establishment and reduce the amount of damage caused by pine weevil the following season. The experiment was conducted in southern Sweden and in south-eastern Norway with an identical experimental design at three sites in each country. On each site, Norway spruce seedlings with or without insecticide treatment were planted at four different planting times: August, September, November and May the following year. In Sweden, the proportion of untreated seedlings that were killed by pine weevils was reduced when seedlings were planted at the earliest time (August/September) compared to late planting in November, or May the following year. This pattern was not found in Norway. The average length of leading shoot, diameter growth and biomass were clearly benefited by planting in August in both countries. Insecticide treatment decreased the number of seedlings killed or severely damaged in both Norway and Sweden.     

Initial moisture stress,budbreak and two-year field performance of three morphological grades of slash pine seedlings

This study examined the relationship between root collar diameter, plant moisture stress and budbreak in three morphological grades of bareroot 1+0 slash pine (Pinus elliottii Engelm.) nursery seedlings and assessed the role of these parameters in predicting field performance potential under operational conditions. Two months after outplanting seedlings with small (3.2 mm) diameters exhibited greater signs of moisture stress than those with the largest (4.7 mm) diameters, as determined by lower xylem pressure potential values. Intermediate and large-sized seedlings (diameter >3.2 mm) showed earlier budbreak than smaller seedlings with more rapid shoot elongation after planting and had significantly greater survival rates for two years after planting on both a moist flatwoods and a dry sandhill planting site. However, after two years on the more favorable moist site, height and diameter measurements of seedlings with significantly smaller diameters initially did not differ from those of intermediate sized seedlings (diameter >3.2 and <4.7 mm). Large seedlings had greater second-year leader and diameter increments and attained greater total height and diameter after two years on both sites. Decreasing the proportion of smaller seedlings included in the field performance analyses increased overall mean plantation survival while increasing the proportion of large seedlings increased mean two-year total height and diameter as well as annual growth increments.     

Field performance of Scots pine (Pinus sylvestris L.) seedlings planted in disc trenched or mounded sites over an extended planting season

Economic pressures have driven an ever-widening period during which foresters use machines to plant Scots pine (Pinus sylvestris L.) seedlings. In Fennoscandia, this period has recently stretched to the entire growing season. To evaluate the performance of seedlings planted during this extended period, three experiments were carried out in Central and Northern Finland over 2 years. One-year-old and current-year seedlings were planted in mounds or disc-trenched furrows when soil temperatures were >0°C. When 1-year-old seedlings grown for spring planting and overwintered outdoors were planted after mid-June, more needles browned and growth was reduced, possibly because seedlings were oversized with respect to planting density and the volume of growth media. When current-year seedlings sown in spring were planted from July to November, those planted in late September and October grew less in later years than those planted earlier, but survival was unaffected. No large differences in field performance were found with respect to whether seedlings were planted in mounds or disc-trenched furrows. In conclusion, Scots pine seedlings can be machine planted in mounds or furrows during May and early June (later in the North) and then continued from early August until late September, provided climatic conditions in late spring and early autumn are typical and similar to those experienced in Central Finland.     

Ecophysiological characteristics of Taiwan alder (Alnus formosana) seedlings adapted to the subtropical region

We investigated several ecophysiological characteristics of seedlings of a low-elevation (100-200 m) and a high-elevation (2000-2400 m) population of Taiwan alder (Alnus formosana Makino) from subtropical Taiwan. Both populations had a wide optimal temperature range for photosynthesis, and there was little difference in the optimal temperature range for photosynthesis between populations. Photosynthetic rate (P(N)) was near maximal from 20 to 35 degrees C when seedlings of both the low-elevation and the high-elevation populations were acclimated at a day/night temperature of 30/23 degrees C. When seedlings were acclimated at a day/night temperature of 20/10 degrees C, P(N) was near maximal over the range 15-35 degrees C in the low-elevation population and 15-30 degrees C in the high-elevation population. Compared with nine other tree species native to Taiwan, Taiwan alder had a high P(N) and stomatal conductance (g(s)) under well-watered conditions. Reflecting its higher transpiration rate, Taiwan alder had a significantly greater leaf-air temperature difference than camphor (Cinnamomum camphora (L.) J. Presl), a co-occurring lowland tree species with leaves similar in shape and size to those of Taiwan alder. Despite higher g(s), high root and shoot hydraulic conductances enabled Taiwan alder to maintain higher leaf water potentials than camphor under well-watered conditions. We conclude that both photosynthetic characteristics and water relations are important factors enabling Taiwan alder to adapt to a wide temperature range, thereby ensuring its success at both high and low elevations in subtropical Taiwan.     

Effect of seed source elevation on bud opening of Yezo spruce (<Emphasis Type="Italic">Picea jezoensis</Emphasis>)

Spring frost damage is one of the obstacles to be overcome in establishing a Yezo spruce (Picea jezoensis Carr.) plantation. The timing of bud opening of Yezo spruce seedlings cultured from seeds collected at three different elevations (420, 700, and 1200m) in the Tokyo University Forest in Hokkaido was observed at two planting site elevations (610 and 750m) to investigate whether seed source elevation or planting site elevation affects the bud opening date. At both planting sites the bud opening dates were not significantly different among the seedling groups from different seed source elevations. On the other hand, bud opening dates of seedlings planted at the lower elevation site were significantly earlier than those planted in the higher elevation site. It could be deduced from this study that the environment of the planting site rather than seed source elevation affects the bud opening date of Yezo spruce.     

无患子实生苗苗期生长动态研究

在福建省顺昌县开展无患子播种育苗试验,重点研究了其苗期生长动态,掌握无患子在一年中的生长特性,研究结果表明:无患子实生苗的苗高生长高峰期在6月到9月,其中以7月到8月生长最快,生长量占总生长量的41.8%,进入9月后苗高生长放缓;地径增长旺盛时期在8月至9月,生长量占总生长量的20%左右。进入10月后,无患子实生苗的生长逐渐以增粗为主,11月后,苗高生长基本停止。复叶片数的变化趋势与苗高基本一致,即生长高峰期出现在7-8月间。11月后幼苗陆续落叶,进入休眠期,因此,复叶片数出现生长曲线出现回落现象。同时,单株最大小叶叶长和叶宽的增长高峰期也分别出现在7月和8月。无患子实生苗从8月上旬开始有单株萌发侧枝, 8-10月单株侧枝数增加较为迅速,11月后侧枝基本停止萌发。但侧枝基径和枝长的生长并未有明显放缓或停滞。说明,此时的地上部分物质积累主要用于侧枝的生长。     

Physiological Characteristics and Carbohydrate Contents of Spring-lifted Picea glauca Bareroot Seedlings Following Low-temperature Storage

This study examined the effects of low-temperature storage of white spruce [ Picea glauca (Moench) Voss] bareroot seedlings to determine whether the time between lifting and planting of spring-lifted seedlings could be extended. Seedlings were lifted from the nursery beds on May 4, 1994, and stored at- 2C (frozen storage) and 4C (cold storage) for 3, 5 and 7 weeks. Frozen storage of spring-lifted seedlings resulted in an increase in sugar levels in roots and needles that progressed with storage duration. Seedlings stored in cold storage maintained a relatively constant sugar content. Needle starch content decreased with storage duration in both frozen and cold storage. In the roots of cold-stored seedlings, starch content remained relatively constant during storage; however, in the frozen-stored seedlings, root starch levels sharply declined during the initial 3 weeks of storage. The levels of total non-structural carbohydrates (starch and sugars) decreased in both types of storage in needles, but not in roots. However, the decrease was more pronounced in the cold-stored than in the frozen-stored seedlings. Gas exchange, root growth potential and number of days to bud break were similar in frozen- and cold-stored seedlings planted in the greenhouse. However, following planting in the forest, cold-stored seedlings flushed buds earlier than did frozen-stored seedlings. The results indicate that tree nurseries could consider frozen storage of spring-lifted white spruce seedlings to facilitate lifting and planting schedules.     

能源植物麻疯树闽东南引种试验

在福建省南安市进行麻疯树引种育苗,并开展不同海拔和不同立地条件的造林试验。结果表明:种子发芽率平均为81%,造林成活率达92.8%,试验林在冬霜期间没有受冻害,生长良好。当年生试验林9~10月份有少量植株开花结果,单株结果数最多达40粒,至12月份已陆续成熟,初试见效,可为中试和推广提供科学依据和示范。     

Bud development and dormancy in slash and loblolly pine. II. Effects of ethephon applications

Ethephon application on four dates did not induce budset in slash and loblolly pine seedlings. Ethephon promoted slash pine budbreak by 11 days when applied in mid-November and delayed loblolly pine budbreak by 8 days when applied in late November. Mid-November and early February applications of ethephon promoted height growth of both species.     

Chlorophyll fluorescence,root growth potential,and stomatal conductance as estimates of field performance potential in conifer seedlings

After cold storage, conifer seedlings in British Columbia are tested for field growth potential before planting. We compared three tests of performance potential using container-grown seedlings of Douglas-fir, interior spruce, lodgepole pine, and western larch (14 seedlots total). On several autumn dates, seedlings were lifted and stored at −2°C. The following spring we tested stored seedlings for root growth potential (RGP), chlorophyll fluorescence (CF), and stomatal conductance (Gs), and then planted seedlings in nursery beds. We assessed survival and shoot dry weight (SDW) after one growing season. Performance test results were significantly correlated with each other (r ≥ 0.47) but showed different relationships with field performance, which varied with lift date. The best performance predictor was the sum of CF and RGP (R ² = 0.79 for 78 seedlot by lift-date combinations), which minimized the risk of planting poor seedlings and not planting good seedlings. A sum of 83 for CF (Fv/Fm %) and RGP (new roots >1 cm) provided a threshold above which survival and growth were good. For evergreen conifers, Gs was a good performance predictor, but required extra time to measure leaf area. We recommend a combination of CF and RGP to assess vigor of shoot and root systems before planting. Wolfgang D. Binder––Scientist Emeritus.     

Growth,flowering and fruiting of stecklings,grafts and seedlings of <Emphasis Type="Italic">Allanblackia floribunda</Emphasis> Oliver (Clusiaceae)

A study was carried out to assess the growth, flowering and fruiting of stecklings (rooted cuttings), grafts and seedlings of Allanblackia floribunda in Cameroun. Thirty-one individuals of each plantlet type were planted in May 2006. Height, collar and crown diameters were recorded in September and October, while flowering and fruiting were recorded each month from January to December. In 2014, the trees with the greatest height were those from seeds (6.98 ± 0.25 m), followed by those from grafts (1.65 ± 0.23 m) and cuttings (1.09 ± 0.21 m). Grafts started flowering and fruiting 3 years after planting, while seedlings started flowering and fruiting after four and 6 years, respectively. Stecklings still had not flowered 8 years after planting. Fruit weight and length from seed-origin trees are about seven times higher than grafts. Correlations between height and crown diameter were significant and positive irrespective of the nature of the planting material. In conclusion, grafts fruited earlier, while seedlings grew faster and had greater yields than grafts and stecklings of A. floribunda.     

Loblolly pine seed dormancy: constraints to germination.

Stratification by moist chilling is often used to break seed dormancy in loblolly pine (Pinus taeda L.). The role that moist chilling plays at the cellular level in preparing the embryo for germination and early seedling growth was investigated. Moist chilling did not affect the embryo's ability to mobilize seed storage proteins, which is a biochemical marker of early seedling growth. Analysis of in vivo protein synthesis profiles indicated that moist chilling has only a subtle effect on gene expression in the embryo or germinant. The means by which moist chilling affects interactions between the seed coat and the living tissues of the seed also was studied. Although the seed coat is mainly a mechanical barrier to germination, seed coat replacement studies showed that moist chilling alleviates some factor(s) in the seed coat that significantly inhibit germination.