Lifting Dates Research Articles

Assessment of photosynthetic activity of nursery-grown Piceaglauca seedlings using an integrating fluorometer to monitor variable chlorophyll fluorescence

Photosynthetic activity of intact nursery-grown white spruce (Piceaglauca (Moench) Voss) seedlings was assessed by measuring CO2 exchange (apparent photosynthesis) and normalized, integrated variable chlorophyll fluorescence emission. Agreement between fluorescence and apparent photosynthesis indicated that photosynthetic inactivation of seedlings from selected seedlots began in mid-August and approached completion in late October. Inactivation occurred somewhat earlier in northern seedlot seedlings than in those from a more southerly provenance. Seedlings tested in late October showed significant photosynthetic inactivation, as indicated by both fluorescence and apparent photosynthesis. These seedlings also had passed the −18 °C frost hardiness test currently used in British Columbia as an indicator for safe lifting. On removal from −2 °C storage, seedlings lifted and stored according to nursery practises showed fluorescence emission indicative of photosynthetic reactivation and also had high root growth capacity scores. Low root growth capacity scores were associated with delayed or incomplete photosynthetic reactivation. These results show that fluorescence assessment provides information about the physiological status of white spruce seedlings. Variable fluorescence assays are nondestructive and can be made and interpreted within minutes. As an indicator of shoot metabolic activity, fluorescence assessment provides information useful in selecting lifting dates and in evaluating the effects of dark cold storage on white spruce 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.

The complementary effects of plant resistance and the choice of sowing and harvest times in reducing carrot fly (Psila rosae) damage to carrots

SUMMARYThe benefits of combining a partially‐resistant carrot cultivar with different sowing and lifting dates to reduce carrot fly, Psila rosae, damage were investigated at Wellesbourne in 1983 and 1984‐85. The partially‐resistant cv. Sytan was less damaged and supported fewer insects than the susceptible cv. Danvers on all lifting dates. The estimated reduction of carrot fly larvae on Sytan compared with Danvers ranged from 33 to 95%. Nine combinations of sowing and lifting dates provided more than 75% marketable roots of Sytan compared with only three combinations of dates for Danvers. An early June sowing of both cultivars provided roots of a marketable size with the least attack. More than 90% of Sytan roots were still marketable in December and fewer insects were produced by the end of the season on these roots than on those sown earlier. In addition, sowing in June decreased the number of pupae produced on cv. Danvers by 10 times compared with earlier sowings. Combining partial resistance with specific sowing and lifting times enabled satisfactory yields of marketable carrots to be obtained in a field infested by high populations of carrot fly.

Changes in loblolly pine root growth potential from September to April

Loblolly pine (Pinustaeda L.) 1 + 0 seedlings were periodically hand lifted from a Virginia nursery to determine how root growth potential (RGP) varied between September and April. Several seedling characteristics, RGP, and shoot phenology were recorded for each lift date in 1983–1984 and 1984–1985. An attempt was made to relate RGP variation to changes in the nursery environment and to shoot phenology. Root growth potential variation was consistent between years and was more closely related to shoot phenological changes than to short-term environmental changes. During the development of dormancy, RGP was low, RGP increased when shoot activity resumed during the RGP tests (late winter, early spring), and declined as active shoot elongation began in the nursery. When RGP was low, elongation of existing lateral roots primarily contributed to the new root systems, but as seedling metabolism increased in the late winter, new root initiation also contributed to new root systems. Absolute differences in RGP between years may be related to the fibrosity of seedling root systems.

Relationships among bud dormancy status, cold hardiness, and stress resistance in 2+0 Douglas-fir

An experiment was conducted to ascertain what relationships might exist among dormancy status, cold hardiness and stress resistance in 2+0 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), seedlings. Seedlings were lifted from a western Washington nursery on six dates spanning the 1980–81 lifting season. On each date samples of seedlings were subjected to the following treatment: (1) tumbling for 5 minutes, (2) desiccation of roots for 30 minutes at 30°C and 2.1 kPa vapor pressure deficit, (3) exposure of shoots to temperatures of −10°C, −15°C or −20°C for two hours and (4) unstressed control. On two lift dates sub-samples of seedlings were placed into −1°C storage and held for two months before the above stress treatments were administered. Bud dormancy status was determined, using a bud break test, on seedlings from each lift date before and after storage. After one growing season in the field percent survival, vigor, height growth and shoot and root weight were determined on stressed and unstressed seedlings. Survival and vigor were less affected by the stress treatments than were height and weight. Severity of stress was in the order −20°C > −15°C > desiccation > handling > −10°C. Degree of cold injury was directly related to seedling dormancy status whether dormancy status had been attained in the nursery from natural chilling or in frozen storage. Seedlings in a mid-range of dormancy release (between deep rest and quiescence) were most resistant to all imposed stresses.

Physiological quality of lodgepole pine and interior spruce seedlings: effects of lift date and duration of freezer storage

Owing to frozen ground, nurseries in interior Oregon, Washington, and British Columbia are often unable to lift bare-root seedlings during midwinter when they are in peak physiological condition. Therefore, seedlings are normally lifted in the fall and planted either immediately or after overwinter storage, or lifted in the spring and planted either immediately or after brief storage. The objective of this study was to ascertain which of the above strategies produced planting stock with the highest physiological quality. The species evaluated were lodgepole pine (Pinuscontorta Dougl.) and interior spruce (Piceaglaucaengelmannii complex). Seedlings were grown in a Weyerhaeuser Canada nursery near Armstrong, B.C., and lifted on nine dates spanning early October 1982 to late March 1983. Seedling quality was evaluated at each lift date and following 2 and 6 months in freezer (−1 °C) storage. Evaluations consisted of measurements of dormancy release index, root growth potential (RGP), stress resistance (SR), and frost hardiness (FH). The main effects of lift date and storage duration were generally highly significant on all seedling-quality attributes. Lift date × storage duration interactions were also highly significant in most cases. Dormancy weakened throughout winter in the nursery, with accumulated chilling. Storage slowed the release of dormancy for most lift dates. RGP was very high in fall-lifted seedlings, but declined rapidly after storage. RGP again increased in late winter, but was not appreciably affected by storage except for March-lifted seedlings. SR was relatively high in fall-lifted seedlings and very low in spring-lifted seedlings. SR was also reduced by storage, especially after 6 months. However, SR did not fall as rapidly in stored seedlings as it did in seedlings left in the nursery bed. FH was −30 °C in early October; during midwinter FH was beyond the limit of measurement (−40 °C). Seedlings of both species appeared to deharden in storage, but at a relatively slow rate. The best operational strategy seems to be fall lifting, beginning November 1, with overwinter freezer storage. Spring-lifted seedlings tended to exhibit low RGP, low SR, low FH, and poor storability.

Wound healing in potato tuber tissue. 1. Effects of maturity at harvest

Potatoes of cvs Record (maincrop) and Red Craigs Royal (second early) were harvested at intervals from 22 August to 14 October. Half of the plots were mechanically defoliated on 22 August, by which date haulms of cv. Red Craigs Royal were largely dead. Tubers of cv. Record were immature at the first lifting date and matured thereafter, particularly after defoliation. Wound healing rates were assessed from the ability of discs of tuber tissue, cut the day after harvest, to become resistant to the loss of water vapour as suberization progressed at high relative humidity. Cv. Red Craigs Royal showed little variation in wound healing rate. Wound healing in cv. Record became more rapid with increasing maturity, particularly after defoliation when it reached a maximum by 1 October. After storage until March in the following year, the effect of maturity at lifting on wound healing rate was no longer evident.

Early forcing of narcissus: The effects of lifting date and stage of floral development at the start of cooling

Early Narcissus flowers may be obtained if bulbs are lifted early from the field, warm-stored (35°C) and then cool-stored (9°C) before forcing in a glasshouse. The earliest satisfactory forcing was investigated, in ‘Carlton’ and ‘Fortune’, by lifting weekly from 27 May to 22 June, and storing at 17°C for 0–7 weeks between warm- and cool-storage. Storage at 17°C is usually intercalated to allow the completion of flower differentiation prior to the start of cool storage. After warm-storage, the bulbs lifted on 27 May and 22 June had reached Stages Sp and A2 of flower differentiation, respectively; 5–7 weeks of 17°C-storage were then needed to reach complete flower differentiation (Stage Pc). Cool storage was therefore begun with bulbs ranging from Stage Sp to Stage Pc. The earliest cooled bulbs had progressed only to Stage A2, and all others to Stage Pc, after 14–16 weeks of cool storage. No floral defects (e.g., split paracorolla) were noted in any treatment, but in ‘Carlton’, about half the bulbs lifted on 27 May and stored for 0 or 1 week at 17°C did not yield a flower, due to failure of the scape to elongate and death of the flower bud within the spathe. Duration of the glasshouse period was reduced by later lifting and by longer 17°C-storage, but following lifting on 15 or 22 June and 2 or more weeks at 17°C, differences were trivial. For flowering within 30 days in the glasshouse, 5 or 6 weeks' 17°C-storage was needed with 27 May lifting, reducing to 1 week at 17°C after 22 June lifting. Flowering within 21 glasshouse days was achieved only after 15 or 22 June lifts followed by 4–5 weeks at 17°C. The earliest flowers in ‘Fortune’ (7 November) were produced following 3–5 weeks at 17°C after lifting on 27 May or 1 June, or following 1–2 weeks at 17°C after later lifting. In ‘Carlton’, the earliest flowers (23 November) followed 2–3 weeks at 17°C after lifting between 1 and 15 June, or 0–1 weeks at 17°C after the last lifting date (22 June). Following the use of 3 weeks' 17°C-storage, flowering date was about equal, irrespective of lifting date. However, further extension of 17°C-storage resulted in a delay in flowering date. Scape length increased irregularly with longer storage at 17°C; scapes were taller following later lifting (8–22 June) than following earlier lifting. Differences in flower diameter between treatments were relatively small.

Fall Lifting Dates, Overwinter Storage, and White Pine Seedling Performance

The effects of the date of fall lifting on post-planting performance of overwinter stored 3 + 0 white pine were studied for two types of containers — the regular kraft-polyethylene bag and the polybin (a sturdy polyethylene bin with a peg-down cover, approximately 50 × 60 × 30 cm deep). Plantings of the stored stock (−3 °C) and of fresh stock from the same seedbeds were made. Second-year survival was taken and measurements of total height and terminal growth obtained.The results indicate that the Degree-Hardening-Days (D-H-D; cumulative daily differences of the minimum below base 50°F from soil temperatures at 15 cm depth) for fall lifting of white pine should be about 300 (D-H-D = 165 on base 10 °C). The previous suggestion of D-H-D = 225 (or D-H-D = 125 with base 10 °C) is now considered too low for safe storage. Polybins may be slightly inferior to kraft bags for storage of white pine because of the imperfect air seal.

Provisional guidelines for fall lifting for frozen overwinter storage of nursery stock

An experiment was started in the fall of 1972 to study the effects of the date of fall lifting on the post-planting performance of overwinter stored white spruce and jack pine. Storage at two temperatures was used, 0°F (−18 °C) and 26°F (−4 °C), with the former a failure, the latter successful. Spring planting indicated that "too early" outplanting is possible. Stored white spruce may be used to extend the planting season into late spring, but not jack pine.Degree-Hardening-Days, D-H-D, i.e. cumulative daily differences below 50°F from soil temperatures at 15 cm depth, is suggested as a possible criterion of stock readiness for storage. White spruce was about 200 D-H-D and jack pine about 375. By inferences from other experiments white pine is about 225 D-H-D and red pine about 300.

Derivation of the springtime starch increase in balsam fir (Abies balsamea)

The contents of starch, total sugar, crude fat, and moisture were determined during the spring (late March until mid-June) in needles, bark, and wood of 1-year-old balsam fir shoots variously shaded, defoliated, and girdled in late March. The starch content in control shoots peaked during the first week in June, about the time vigorous current shoot elongation began. Shading reduced the concentrations of both starch and total sugar throughout the experimental period, while defoliation decreased them after about mid-spring. Girdling increased the carbohydrate content during early spring in both shaded and unshaded shoots, but decreased it in defoliated shoots. It is concluded that the bulk of the starch accumulating in conifers during the spring is derived from current photosynthesis, the rest being regenerated from carbohydrates produced during the previous year and stored overwinter. Timing the lifting date to maximize the springtime accumulation of starch might be an important consideration when transplanting conifer seedlings.

ROOT PRUNING OF NURSERY STOCK

In the fall of 1958, an experiment was begun at Midhurst Nursery to study the effects of root pruning at different stages of growth and at two depths, on 3-0 stock of white spruce (Picea glauca (Moench) Voss) and white pine (Pinus strobus L.). Root pruning was done by undercutting broadcast-sown seedbeds at two inch and four inch depths; in the fall as 2-0 (Sept. 16, 1958), in the spring at start of growth (April 30, 1959), during flush of growth (May 28, 1959) and towards end of terminal growth (June 25,1959).Seedbed counts were taken before lifting, in fall 1959, to study mortality. Random samples were taken on date of lifting (Sept. 17, 1959), for laboratory measurements to study effects on seedlings size. Other random samples were planted in experimental designs at Larose Forest. Counts of survival, and measurements of terminal growth were taken at the first, third and fifth year after planting.Results showed no mortality in the nursery but that all root pruning reduced height growth. Root pruning of white spruce after the flush of growth (June 25) increased survival and growth after outplanting, over that of unpruned stock. None of the treatments increased survival or growth of white pine. Depth of root pruning had no significant effect.

The relation between length of growing period and cooking quality of potatoes

1. The scoring system, designed by the Working Group “Potato Quality Research” of the European Association for Potato Research has proved valuable in defining differences in quality properties in potatoes of varying ripeness. 2. Colour and discoloration of cooked potatoes were barely influenced by dates of planting or lifting. 3. Both lifting and planting date influenced texture properties of the varietyLibertas grown on sandy soild in Drenthe. The influence of lifting date was often curvilinear. This curvilinearity was not observed in the influence of planting date (fig. 1 and 2). 4. Interactions were present between “field” and planting date and “field” and lifting date (fig. 4), which means that the influence of these dates varied from field to field. Furthermore, there was an interaction between planting date and lifting date (fig. 3), indicating that the influence of lifting date on texture properties became greater the later was the planting date. Consequently the chance that potatoes are insufficiently mealy by reason ofe.g. an early and severe attack of blight is greater if the farmer has been forced to plant very late. 5. If planted at the normal time (April) and lifted at the normal time (not before the second half of September) the texture properties of the highly blight-resistant varietyLibertas will not deviate much from “normal” (fig. 5). Other varieties will require growing periods of different length, but blight susceptibility will be more important in determining the actual length of the growing period required.

THE EFFECT OF DATE OF PLANTING AND OF HARVESTING POTATOES ON VIRUS INFECTION AND ON YIELD

Experiments during 1953–6 tested the effects of early and late planting of King Edward potatoes on the incidence of virus diseases in the tubers and the suitability of the tubers for use as seed. Plantings were made each month from April to August and tubers were lifted after 12 weeks' growth or after the haulms had died.Aphids began to colonize the early‐planted plots about mid‐June each year, but their multiplication and flying were influenced by weather and varied greatly from year to year. The May‐planted plots usually carried the most aphids. Winged aphids visited the July and August plantings, but few bred extensively though the plants were young and green. The incidence of virus diseases in the tubers was not related to the maximum aphid populations on the plants. Most of the plants that became infected became so by aphids flying from diseased potato plants in the same field, and the late‐planted plots did not escape. Crops planted in mid‐April and harvested in early July produced the fewest virus‐infected tubers.Planting in April and lifting at the end of the season produced most ware‐sized tubers. In plots lifted after 12 weeks, May or June planting produced more ware than April planting. Few or no ware‐sized tubers were produced from July or August planting, and yields of seed‐sized tubers also were poor. Most seed‐sized tubers were produced by the late‐lifted May or June plantings. The date of lifting had little effect on the total number of tubers, but the date of planting affected it greatly. Most tubers were usually set by the May plantings and the number decreased with successive plantings.Early‐lifted immature tubers were easily damaged and were difficult to store. Blighted tubers occurred only in the July or August plantings, which also suffered most from slug and cutworm damage.Infection with leaf‐roll virus reduced yield by about three‐quarters, whether the seed had been lifted early or late the previous year. Healthy or virus‐infected mature seed produced a bigger crop the next year than immature seed obtained by early lifting or late planting.Late‐planted tubers produced more main stems than those planted at the normal time, but growth of axillary shoots was reduced and total leaf area remained small, even when the plants were not attacked by blight.

The influence of date of lifting and method of storing on loss of onion bulbs harvested in 1943

Date of lifting experiments with four varieties of onion at two centres are examined in relation to the incidence of losses in store, and at one centre the effects of indoor and outdoor storage are compared. Losses due to Botrytis, eelworm infection and sprouting are treated separately, and the practical significance of the results is discussed.