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- Author or Editor: J. T. A. Proctor x
The growth and cropping of apple trees, as with other crops, is dependent largely upon environment. The environment consists of two distinct components, the soil and the atmosphere, which, while sharply divided by the surface of the earth, interact with each other. The aerial component’s influence on production can be considered on three scales. The macro scale and hence macro climate is a regional climate, e.g. the Okanagan Valley of British Columbia. The next scale is the individual farm, or less, where the macroclimate can be modified by factors such as exposure, altitude, slope and aspect. The resultant local climate is the mesoclimate. Microclimate, the third scale, includes detailed studies close to the earth’s surface, and within the orchard and tree.
The development of a complete and healthy early season canopy of spur leaves, and later addition of bourse leaves, is essential for fruit set, fruit growth and quality in apple. The present study was undertaken to evaluate the temporal role of spur leaves and bourse shoots on fruit set, growth and return bloom in three apple cultivars and fruit Ca Level at harvest in two cultivars.
Individual flowering spurs on mature wood of “Cox's Orange Pippin”, “Golden Delicious” and “Crispin” apple trees were modified by removing the spur leaves, the bourse shoot, or both, at full bloom and two, four and eight weeks afterwards. Leaf removal reduced fruit set, yield (as fruit number and not size), fruit calcium level at harvest, and return bloom. Defoliationhad its greatest effect on fruit calcium level when done early in the season and plots of this against treatment time suggested a curvilinear relationship. Return bloom was dependent on the presence of the bourse shoots on the spur but not on spur leaves. Return bloom of all three cultivars declined with the number of fruitlets per spur four weeks after full bloom.
Defoliation (0%, 25%, 50%, 75%, or 100% leaves removed) of apple trees (Malus domestica Borkh.) to simulate loss in photosynthetic area caused by spotted tentiform leafminer (Phyllonorycter blancardella F.) reduced trunk cross-sectional area, yield, and fruiting the following year. Shoot growth responded the year of injury and the following year. Fruit size and maturity also were affected. Punching holes (0, 2, 4, 8 simulated mines of 0.56. cm2) into leaves of mature fruiting trees had no effect on vegetative growth. Fruiting may have been reduced. Leaf punching reduced rootstock growth of small potted apple trees.
American ginseng (Panax quinquefolius L.), was injured by exposure to 20 pphm ozone and/or 50 pphm (v/v) sulfur dioxide for 6 hr daily for 4 days. Ozone induced upper surface leaflet stippling along the veins and interveinaily, and sulfur dioxide induced mild chlorosis to irregular necrotic areas. Ginseng was less sensitive to ozone and as sensitive to sulfur dioxide as ‘Cherry Belle’ radish (Raphanus sativus L.) and ‘Bel W-3’ tobacco (Nicotiana tabacum L.).
Leaf removal, cane girdling, and 14C translocation patterns were used to study source-sink relationships of primocane-fruiting (PF) red raspberries. Although the leaves in the reproductive zone were most important for vegetative and reproductive development, compensatory effects between the cane leaves were evident. When 14C translocation was studied in the reproductive portion of the cane, the lateral closest to the 14C-treated leaf was the major sink for carbohydrate from that leaf, independent of leaf position or reproductive development. Thereafter, partitioning to leaves and/or flowers or fruits above the 14C-treated leaf was related to leaf phyllotaxy 75% of the time.
Field experiments including supplementary trickle irrigation (IR), IRT-76 plastic film (PF), and straw mulch (STR) treatments were conducted during 1993 and 1994 to determine the influence of root-zone temperature and soil moisture status on carbon assimilation and dry mass distribution, and soil and plant nutrient content, during the establishment of Rubus idaeus L. `Heritage' primocane-fruiting raspberries. The IR, PF, and STR treatments were reapplied after the 1993 establishment year to examine their effects on an established, hedgerow planting. Physical environment, vegetative and reproductive data were collected. PF increased root and shoot mass, total flower number, and total berries harvested. Maximum leaf net photosynthetic (Pn) rates were observed under cool air temperatures and root-zone temperature of 25 °C. Field Pn measurements indicated that there was no seasonal decline in Pn. Mulch treatments however, were not beneficial to the established (i.e., 2-year-old) hedgerow planting. The root system of the 2-year-old planting was largely confined to an area within the foliage wall and also at a greater depth from the mulch treatments. Therefore, beneficial effects of mulch management on the growth and development of raspberries may be limited to the establishment year.
Two selections and two cultivars of red raspberry (Rubus idaeus L.) were evaluated for cold hardiness in vitro. Tissue-cultured shoots were exposed to temperatures from 0 to –18C and samples were removed at 2C intervals. Injury was assessed by a visual rating of tissue browning after freezing. Only shoots subjected to step-wise acclimation at low temperatures before freezing revealed significant differences among the four types in the lowest shoot survival temperature. Acclimation treatments increased the lowest survival temperatures of in vitro shoots by a mean of 3.1C. The hardiness obtained from this screening method agreed with that of winter survival in the field. Ranking, from the most to least cold hardy, was `Boyne', Gu 72, Gu 63, and `Comox'.
`Autumn Bliss', `Heritage' and `Redwing' were grown in a controlled environment setting at three day/night temperature regimes (30/25, 25/20, 20/15C) at either 12 or 16 hour photo periods. Vegetative (height, diameter, node number, leaf area, leaf, cane and root dry weight) and reproductive (precocity, numbers of fruiting laterals, flower number and dry weight) parameters were analyzed. Optimum vegetative growth was obtained when plants were subjected to short photoperiods (12 hrs) and cool (20/15C) or moderate (25/20C) day/night temperatures. Reproductive characteristics were enhanced when grown under long photoperiods (16 hrs) and moderate temperatures. High temperatures (30/25) reduced cane height due to a decrease in internode length with the greatest reduction occurring under long photo periods. Precocity and flowering was enhanced by long photoperiods especially at cool and moderate temperatures. This may have implications for the reproductive potential of these cultivars when grown in north temperate areas where high temperatures are common for most of the summer.
Tissue survival assessments of red raspberry (Rubus idaeus L.), including cane dieback, bud death, time of cane leaf drop, and growth cessation, were compared to freezing tests of stem portions and buds. Four named cultivars and six Guelph (designated Gu) selections were assessed in the field at two locations in each of two winters and in concurrent controlled freezing tests at one location for one winter. The time of cane leaf drop and of cessation of cane extension growth in the fall were not correlated with field survival. Cane dieback as a percentage of cane length was a better estimate of winter survival than was bud number. Controlled freezing tests of stem portions and buds, and calculation of T40s and T50s indicate that genotypes differed in their relative hardiness throughout the winter. The different methods of field assessment of cold hardiness were well correlated, but not well correlated with controlled freezing tests (4.2% significant correlations). Exclusion of the genotype, Gu 75, which behaved differently in the field than in freezing tests, increased the number of significant correlations to 16.7%.
Ginseng is an herbaceous perennial that grows in the understorey of deciduous hardwood forests and is also cultivated for its highly valued root. The primary method of propagation of ginseng is by seed which requires the breaking of dormancy by stratification, a process which takes 18–24 months. Investigation of factors controlling the growth and development of ginseng plants is a prerequisite to the development of a more efficient system of ginseng propagation. We have recently modulated the morphogenetic potential of geranium roots and stimulated de novo development of shoots and embryo-like structures which later formed whole plants using thidiazuron (TDZ). Our objective was to investigate the morphological changes in seedling and mature ginseng plants induced by TDZ, particularly in relation to root and shoot morphogenesis and economic yield. Applications of TDZ (0.22 and 2.20 ppm), either as foliar sprays or soil watering to greenhouse-grown seedlings over 18 weeks (2 weeks after sowing to 20 weeks when plants were harvested) induced similar effects. These responses included increased stem length and diameter, and shoot and root weight (economic yield). Single foliar applications of TDZ at 62.5 and 125 ppm to 3-year-old field-grown ginseng plants 3 months before harvest increased root biomass (economic yield) by 19% to 23%. Roots of TDZ-treated seedlings and 3-year-old field-grown plants developed thickened secondary roots on the upper part of the taproot. The root-like structure of these secondary roots was confirmed by histology. In addition, TDZ treatments induced adventitious buds on the shoulder of 3-year-old roots. These buds developed into shoots to give multi-stem plants following a period of dormancy, which was overcome with GA3 (gibberellic acid) treatment before planting.