Lateral Shoot Growth Research Articles

Loss of a highly conserved sterile alpha motif domain gene (WEEP) results in pendulous branch growth in peach trees

Plant shoots typically grow upward in opposition to the pull of gravity. However, exceptions exist throughout the plant kingdom. Most conspicuous are trees with weeping or pendulous branches. While such trees have long been cultivated and appreciated for their ornamental value, the molecular basis behind the weeping habit is not known. Here, we characterized a weeping tree phenotype in Prunus persica (peach) and identified the underlying genetic mutation using a genomic sequencing approach. Weeping peach tree shoots exhibited a downward elliptical growth pattern and did not exhibit an upward bending in response to 90° reorientation. The causative allele was found to be an uncharacterized gene, Ppa013325, having a 1.8-Kb deletion spanning the 5' end. This gene, dubbed WEEP, was predominantly expressed in phloem tissues and encodes a highly conserved 129-amino acid protein containing a sterile alpha motif (SAM) domain. Silencing WEEP in the related tree species Prunus domestica (plum) resulted in more outward, downward, and wandering shoot orientations compared to standard trees, supporting a role for WEEP in directing lateral shoot growth in trees. This previously unknown regulator of branch orientation, which may also be a regulator of gravity perception or response, provides insights into our understanding of how tree branches grow in opposition to gravity and could serve as a critical target for manipulating tree architecture for improved tree shape in agricultural and horticulture applications.

Vigor control in ‘McIntosh’ apple trees by growth inhibitors

Abstract We evaluated the effects of two gibberellin biosynthesis inhibitors [Prohexadione-Ca (Apogee ® 250 ppm) and Trinexapac-ethyl (Moddus ® 225 ppm)], on shoot growth of mature ?McIntosh?/M.9 apple trees. The growth regulators were applied 7 days after bloom, when shoots were 5 cm long. Shoot length was measured every 15 days to determine growth rate. Shoots were measured in the lower, middle and upper portion of tree and according type (terminal and lateral shoots). The number of fruits tree -1 , yield and yield efficiency were determined at harvest. After harvest, fruits were classified according to the color. Both growth inhibitors reduced shoot growth rate approximately 30% and reduced the daily growth rate (cm day -1 ) of all types of shoots and in all positions of tree. Daily growth rate was affected by shoot position. Growth rate of shoots located in lower portion of tree was reduced more than for shoots in the upper part of the tree. Likewise, terminal shoot growth rate was reduced less than lateral shoot growth rate. Trinexapac-ethyl (Moddus ® 225 ppm) increased the number of fruits tree -1 and yield efficiency but reduced return bloom about 57% compared to the untreated control and 65% when compared to Apogee ® . Both growth inhibitors had a positive effect on fruit color, which was probably due to improved light penetration into the canopy.

Growth Characteristics of Vitis vinifera L. cv. Cape Riesling

The effect of topping on the growth behaviour of Vitis vinifera L. cv. Cape Riesling vineyard was investigated. Shoot and leaf growth of both topped and untopped vines, can be described as sigmoidal. Shoot (cm) and leaf growth (cm') of the topped vines were significantly more than that of the untopped vines and are attributed to lateral shoot growth. Topping had no effect on bunch development. The development of skin, pulp and seed of both topped and untopped vines expressed as a percentage dry mass per berry can be described by a hyperbolic function for the skin, linear for the pulp and parabolic for the seed.

Prohexadione-calcium, ethephon, trinexapac-ethyl and maleic hydrazide reduce extension shoot growth of apple

Prohexadione-calcium (P-Ca) is widely used to reduce vegetative growth and labour costs associated with manual pruning. Orchard studies were conducted in 2012 and 2013 to determine the response of mature ‘Empire’/M.26 apple trees to individual or combined applications of P-Ca, ethephon (ETH), trinexapac-ethyl (TE), and maleic hydrazide (MH). Sprays were repeated three times at approximately 2-wk intervals starting at petal fall. All compounds reduced extension shoot growth, ranging from 40%–73% in 2012 and 26%–57% in 2013, relative to untreated controls. The greatest reduction in growth was achieved with ETH in one year and P-Ca + ETH and MH in another. The tank-mixed combination of P-Ca + ETH improved vegetative control compared with each compound applied alone. MH caused foliar phytotoxicity and damage to the apical meristem, resulting in the stimulation of lateral shoot growth. Reduction in shoot growth from any of the plant bioregulators (PBR) did not reduce dormant pruning times in the spring followi...

Plantain cultivars (Musa spp. AAB) grown at different altitudes demonstrate cool temperature and photoperiod responses relevant to genetic improvement

Knowledge of plant development in plantains is needed to manage seasonal variation in production and better match critical development phases with appropriate seasons. Plantains have juvenile, mid-vegetative and floral phases leading up to flowering (bunch emergence). We examined whether the juvenile phase showed a cool temperature response, whether the mid-vegetative phase was sensitive to photoperiod and how these phases were related to growth of lateral shoots (suckers) up to flowering. We examined published data of an experiment of five plantain cultivars grown at four altitudes, and therefore temperatures (1000m, 24°C to 2200m, 16°C) within 1° latitude of the equator in the Democratic Republic of Congo. Four of the five cultivars showed a cool temperature response in the juvenile phase. Plants grown in cool temperatures (16°C) ended the juvenile phase after producing 7 leaves. In warmer climates (24°C) 15 leaves were produced before the juvenile phase ended. All five cultivars demonstrated a high capacity to respond to photoperiod in the mid-vegetative phase. There were detectable differences in capacity of the cultivars to respond to photoperiod, Ps. ‘Vuhindi’ had the least capacity (Ps=90) and ‘Musilongo’ and ‘Vuhembe’ the greatest (Ps=145). Across altitudes, suckers began to appear above ground at just after the end of the juvenile phase and there was a strong positive linear correlation (r2=0.97) between the calculated phyllochron (10–27 days) and the proportion of lateral buds that grew into suckers. With a phyllochron of 10 days about 10% of the lateral buds present on the plant produced lateral shoots up to flowering. At 27 days, from 40% to 80% of the lateral buds produced suckers depending on the cultivar. The responses of the juvenile phase to low temperature and the mid-vegetative phase to photoperiod in Musa spp. opens the opportunity to alter plant development and produce cultivars better suited to the climates where they are currently grown and to extend this range.

Photosynthetic and growth responses of Pinus koraiensis seedlings to canopy openness: Implications for the restoration of mixed-broadleaved Korean pine forests

The mixed-broadleaved Korean pine (Pinus koraiensis Sieb. et Zucc.) forest (MBKPF) is a zonal climax ranging from Northeast China to the Far East region of Russia. However, since the 1950s, most of the MBKPFs in Northeast China have become the mixed broadleaved secondary forests due to the heavy forest exploitation by timber harvesting. The natural regeneration of Korean pine is generally poor because of the light limitation in Northeast China. This study was conducted to understand how Korean pine seedlings adapt to different canopy openness (CO) and what would be the minimum CO for its establishment and growth in the natural forest stands. In order to test the hypothesis that Korean pine seedlings have acclimated to low light regimes, the responses of photosynthetic, morphological and growth parameters to light environments were examined in Korean pine seedlings that were field-grown in secondary forests. The results can provide the references for the restoration of MBKPFs in Northeast China. Three-year-old Korean pine seedlings were under-planted in secondary forest stands with three levels of CO at 30%, 15% and 7%, which were created by modifying the branches of the secondary forest stands. After one year of acclimation under the secondary forest stands, the variations in the physiological and morphological characteristics of the needles as well as the growth parameters were measured. The maximum net photosynthesis (Amax), dark respiration (Rd), needle chlorophyll (Chl) contents and total needle nitrogen (N) contents all responded positively to the increased CO. The total non-structural carbohydrate (TNC), Amax, Rd, and N contents in the 7% stand were significantly lower than those in the 15% and 30% stands (p<0.05). The capture efficiency of excitation energy by open Photosystem II (PSII) reaction centres (Fv′/Fm′) in the 7% stand was the lowest and was significantly different from those in the 15% and 30% stands (p<0.05), although no significant differences were found between 15% and 30% CO (p>0.05). These results indicated that 7% CO seedlings were experiencing some degree of low light stress. The leaf mass area (LMA) and height growth decreased as the CO decreased from 30% to 15% to 7%, while the lateral shoot growth increased. Therefore, needle morphology, tree height and crown growth of Korean pine seedlings displayed a large plasticity in response to variations in light intensities. These findings suggest that Korean pine seedlings can strongly acclimate in the forest canopy by adjusting physiological traits that are associated with light energy distribution in the PSII and by adjusting the morphological features of their needles. These results suggest that the minimum canopy openness required for the survival of P. koraiensis seedlings (4 years old) grown under a canopy should be more than 7%.

The gall inducing insect community on Baccharis concinna (Asteraceae): the role of shoot growth rates and seasonal variations

Resource allocation patterns have been extensively studied on the dioecious shrub Baccharis concinna Barroso (Asteraceae) in rupestrian grasslands in Brazil. Female plants have longer apical shoots, more flowers per shoot, and greater leaf, flower and stem biomass on apical shoots while male plants have longer lateral shoots. Otherwise, no differences were observed in total biomass of vegetative parts between male and female plants. We further investigated the relationship between lateral shoot growth rates and the richness and abundance of galling-insect species on this host plant. Male plants had longer lateral shoots due to greater growth rates throughout the year. On the other hand, galling-insect richness and abundance did not differ between male and female plants throughout the year. Gall-inducing insects showed greater richness and abundance in the drier months of the year while lateral shoot growth rates were greater during the rainy season. In conclusion, male plants allocated more resources to the growth of lateral shoots when compared to female plants, but this differential growth did not reflect on male plants being more attacked by galling-insects.

Dry matter and leaf area partitioning, bud fertility and second season growth of Vitis vinifera L.: Responses to notrogen supply and limiting irradiance

Potted Vitis vinifera L. plants were grown under controlled environmental conditions at five different levels of nitrogen (0, 1, 5, 10, 100 mM NH 4 NO 3 ) in combination with two different levels of irradiance (30 and 140 µmol m -2 s -1 PAR, respectively) during bloom. The immediate, whole season and second year effects on vegetative growth were assessed, and bud fertility and rate of development were evaluated. The optimum N addition level was 1 mM NH 4 NO 3 for root growth and 5 mM for shoot growth, respectively, both after bloom and at the end of the first growing season. This growth response to N supply became apparent only in the higher light treatment and was mainly due to an N-induced enhancement of leaf and lateral shoot growth. Low-light stress also strongly enhanced the number of new leaves and laterals, but total dry matter production was reduced and did not respond to N nutrition. Light restriction increased the specific leaf area by 52 % and the leaf area ratio by 37 % but did not affect the leaf weight ratio. The leaves of N-deficient vines, in particular in combination with light stress, senesced earlier than those of vines with sufficient or excessive N availability. The light effect on shoot growth in the second season was inverted compared with the first season, and the peak response to N supply was shifted towards 100 mM NH 4 NO 3 . Limiting light conditions during inflorescence initiation severely reduced the bud fertility but advanced the date of bud break and enhanced the rate of development of the new shoots in the subsequent season. The optimum N supply rate for both bud fertility and development was 5 mM NH 4 NO 3 . Bud mortality was not affected by either treatment factor. These data indicate that the bloom period is critical for reproductive development of grapevines, with high sensitivity to environmental stress. They also emphasize the importance of nutrient reserves in the permanent structure for both compensatory and early season growth.

Quantitative trait loci analysis of lateral shoot growth in tomato

Branching is an important agronomic trait to determine plant architecture and fruit yield. In tomato, the regulatory mechanisms of shoot branching patterns have been studied mainly in mutants defective in meristem identity. Little is known about quantitative trait loci (QTLs) and their genetic interaction (epistasis) in lateral shoot development. Here, the genetic control of lateral bud outgrowth initiation and subsequent lateral bud development into branches were investigated. We used a BC1F7 population developed from Solanum lycopersicum (SL) and its close wild relative Solanum pimpinellifolium (SP) to measure the number of leaves on primary shoot (LN), the proportion of nodes with lateral buds (LS0) and lateral branches longer than 5cm (LS5) and 10cm (LS10) on main axis, the proportion of nodes with secondary lateral branches longer than 1cm (LSLS1) on primary lateral branches, and the lengths of the longest primary and secondary lateral branches (LLSL1 and LLSL2, respectively). Composite interval mapping detected 17 additive QTLs; those for LS5, LS10, and LLSL1 clustered near C2_At5g49480 or LEATPACb on chromosome 1 and LEOH361 on chromosome 4. One epistatic (QTL×QTL) interaction was identified for LS10 QTLs on chromosomes 1 and 12, where recombinant-type alleles increased lateral bud development into primary lateral branches. We analyzed further the QTLs clustered on chromosome 1 using two BC3F4 populations containing introgression region from the SP, which revealed the co-location of QTLs for lateral shoot development and days to flowering time. These results suggest that lateral shoot development is regulated by some additive and epistatic QTLs, some of which possibly exhibit a pleiotropic effect on flowering time.

Increasing Nitrogen Availability at Veraison through Foliar Applications: Implications for Leaf Assimilation and Fruit Ripening under Source Limitation in ‘Chardonnay’ (Vitis vinifera L.) Grapevines

Viticulture in Michigan is often limited by cool and humid climate conditions that impact vine growth and the achievement of adequate fruit quality at harvest. Sugars, pH, acids, and yeast available nitrogen (YAN) are indices of quality and, as such, of suitability for wine production. The aim of this study was to evaluate the efficacy of foliar nitrogen (N) fertilization applied as a 1% w/v urea solution at veraison as a method to increase canopy N availability during the fruit ripening stage. To test the effect on different source sink conditions, we imposed three levels of defoliation (0%, 33%, and 66% of leaves removed per vine) and measured net photosynthetic rate (Pn), leaf efficiency parameters, yield components, and fruit quality parameters. Apical leaf Pn was increased by the 33% defoliation (+12% from the undefoliated control) and by the urea application (+6%) 2 weeks after veraison. In basal leaves we observed a reduction in chlorophyll content (SPAD) and maximum photochemical efficiency of PSII (Fv/Fm) as a result of the defoliation treatment and secondarily by the N application, which resulted in a reduction in Pn. Therefore, mean shoot Pn was unaffected by the treatments. Although neither main nor lateral shoot growth was increased by any defoliation treatment, both percent soluble solids (%SS) and berry weight were significantly reduced by the 66% defoliation treatment. Application of urea increased yeast available amino acids by 20% but did not impact %SS or other chemical parameters indicating a different accumulation pathway for sugars and amino acids in the berry.

SALINITY EFFECTS ON GROWTH AND APICAL DOMINANCE IN PHASEOLUS VULGARIS L.

The effect of irrigation with saline nutrient solutions on the growth of the main stem and lateral shoots of two varieties of dwarf bean (Phaseolus vulgaris cvs. Balady and Black Valentine) was studied. Saline culture solutions were prepared by adding NaCl to Pfeffer's nutrient solution. Salinity, especially at 20 meq NaCl, promoted the growth of the main stem in cv. Balady, whereas that of cv. Black Valentine was promoted by up to 60 meq NaCl. The growth of lateral shoots was enhanced with salinity up to 20 meq NaCl in cv. Balady and 40 meq Nad in cv. Black Valentine, although higher concentrarations were not suppressive as compared with the control. The levels of some mineral elements in the leaves were determined. Total nitrogen and sodium concentrations in both varieties were increased, whereas phosphorus and potassium concentrations were progressively decreased by salinity.

GROWTH CORRELATIONS IN EUONYMUS JAPONICUS THUNB. (CELASTRACEAE)

Euonymus japonicus Thunb. is an evergreen shrub with a periodic growth pattern consisting of several growth flushes per year. In each growth flush, 9–11 nodes are added to the stem length. The nodes formed at the beginning of a growth flush are short and bear scale-like leaves. In the middle, the nodes are longer and become shorter again toward the end of the growth flush. The growth of E. japonicus was inhibited when the plant was maintained at a day/night temperature of 17/12°C. Growth inhibition by low temperature was counteracted by gibberellin treatment. The results of experiments carried out with specially prepared single-or two-stem plants proved the existence of a growth inhibition gradient along the stem in every growth flush. Growth of new lateral shoots was more vigorous on the proximal regions of the stem produced by earlier growth flushes than on the distal regions produced by newer flushes. The presence of unpruned stems bearing an apical bud caused growth inhibition on the short and long pruned stems of the same plant. However, there was no growth inhibition when the apical bud was removed.

Regulated Deficit Irrigation based upon optimum water status improves phenolic composition in Monastrell grapes and wines

The effects of three deficit irrigation strategies pre and post-véraison, on soil–plant water status and their influence on leaf area, cluster microclimate, fruit growth, yield and berry and wine quality were evaluated for three years (2009–2011) in field-grown Monastrell grapevines under semiarid conditions in South-Eastern (SE) Spain. Three treatments were applied: a Sustained Deficit Irrigated treatment (SDI) was irrigated at 40% of the Crop Evapotranspiration (ETc) throughout the orchard cycle, 211mmyear−1; a Regulated Deficit Irrigation treatment 1 (RDI-1threholds) received 30% ETc (2009 and 2010) or 20% ETc (2011) from budburst to fruit set. From fruit set to harvest the irrigation was established by maintaining an average mid-day stem water potential (Ψs) within the range −1.2>Ψs≥−1.3MPa and from véraison to harvest within the range −1.3>Ψs>−1.4MPa, 106mmyear−1); And a Regulated Deficit Irrigation treatment 2 (RDI-2cutoff-thresholds) received 20% ETc (2009 and 2010) or 10% ETc (2011) from budburst to fruit set and from fruit set to véraison an irrigation cut-off was applied. Then, from véraison to harvest, an irrigation recovery was applied based on maintaining mid-day Ψs within the range of Ψs proposed: −1.3>Ψs>−1.4MPa (similar to RDI-1), 76mmyear−1). A recovery of irrigation at 40% ETc was used in all treatments from harvest to leaf fall. The RDI-1thresholds strategy, which applied moderate water stress during pre and post-véraison, saved water, reduced vine vigor and vegetative development, controlled yield, improved cluster microclimate, maintained similar or even higher sugar content in the berries and improved the phenolic composition of Monastrell grapes and wines compared to the SDI and RDI-2 strategies. RDI-1thresholds vines increased color intensity, sugar and total anthocyanins in the berries, and color intensity, alcohol content, concentration of polyphenols and total anthocyanins and flavonols in the wines. In contrast, in the RDI-2cutoff-thresholds strategy, which had complete irrigation cut-off during the pre-véraison period (from fruit set to véraison) substantially decreased lateral shoot and berry growth at véraison, and also excessively reduced photosynthetic activity, water status pre-véraison and the resilience of photosynthesis during véraison- early ripening period, which was not beneficial from a physiological and agronomical point of view for Monastrell grapevines in SE Spain.

Sprouts seasonal elongation of two olive cultivars in a high-density orchard

The new high-density cropping systems (>1200 trees ha-1) represent a very interesting proposal for olive orchard profitability. It is crucial to know the morphology and the dynamics of sprout elongation of a cultivar in order to fully assess its suitability for a high-density olive orchard. For this reason we planned a research on two cultivars, Coratina and Arbequina, in a high-density orchard. The apical sprouts elongation of Arbequina early stopped at fruit set without a further step, while Coratina showed a little growth flux after pit hardening. Similar trends showed the lateral proleptic sprouts. Only the sylleptic sprouts of both cultivars had a second period of activity. In all cases, the sprouts elongation finished at the end of summer, when oil accumulation started. Coratina showed higher apical shoot growth and internodes mean length than Arbequina. On the contrary, Coratina showed lower lateral proleptic shoot growth and nodes number than Arbequina, but the same internodes mean length. No significant differences were observed between cultivars for growth, nodes number and internodes mean length of sylleptic shoots. The differences observed between the two cultivars could be explained considering their different vigour. The introduction of this innovative cropping system is allowed to register a considerable reduction of production costs. The result is a considerable increase in the economic performance of the olive grove and a consequent reduction in the unit cost for kg of oil. These data are very useful for varietal choice and field management in high-density orchards and then for new olive breeding programs.

The Florigen Genes FT and TSF Modulate Lateral Shoot Outgrowth in Arabidopsis thaliana

Successful sexual reproduction of a plant with prolific seed production requires appropriate timing of flowering and concomitant change of architecture (e.g. internode elongation and branching) to facilitate production of the optimal number of flowers while enabling continued resource production through photosynthesis. Florigen is the prime candidate for a signal linking the two processes. Growth analysis of lateral shoots in mutants of FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF) revealed a delay in the onset of outgrowth and a reduction of the growth rate in ft plants in long-day (LD) conditions and in tsf plants in short-day (SD) conditions. Thus, as in the case of floral transition, FT and TSF play dominant roles in LD and SD conditions, respectively, in the promotion of lateral shoot development. Differential expression patterns of the two genes were in good agreement with their differential roles both in the floral transition and in lateral shoot development under contrasting photoperiod conditions. By manipulating florigen production after bolting of the primary shoot, it was shown that florigen promotes lateral shoot growth independently of its effect on the floral transition of the primary shoot. Analysis of growth and gene expression in lateral shoots of the mutants suggests that the loss of florigen leads to a reduced rate of flower formation on lateral shoots. Together, we propose that the two florigen genes are an important key to linking the floral transition and lateral shoot development to maximize the reproductive success of a plant.

Determination of the Origin of Vigorous Shoots Generated from Particle-bombarded Chrysanthemum Shoot Tips

Vigorous shoots in chrysanthemums (Chrysanthemum morifolium) often develop from shoot tips (apical meristems with two leaf primordia) cultured in vitro following particle bombardment. The average fresh weight of regenerated shoots from a bombarded shoot tip of chrysanthemum ‘Jinba’ was 10 times more than that regenerated from unbombarded shoot tips. The average number of leaves per bombarded shoot tip was also more than that from an unbombarded shoot tip. The average number of leaves developing from a shoot tip increased with an increase in the amount of gold particles shot into the shoot tips. In addition, when the area destroyed in a shoot apical meristem (SAM) was varied by bombardment through nylon mesh with different pore sizes, the total number of leaves produced from each shoot tip increased with the size of the destroyed SAM area. Knowing the origin of these vigorous shoots, which may be from the bombarded meristem or from the lateral meristems, is important for the screening of transgenic plants. When the entire surface of a SAM was destroyed by bombardment, it was unable to rebuild itself; instead, lateral meristems were initiated at the base of the leaf primordia. Furthermore, the initiation of lateral meristems at the base of the leaf primordia was also observed in instances of restoration of the area of a partially destroyed SAM. This result indicates that vigorous lateral shoots initiate and develop from the bases of leaf primordia when SAMs are damaged to varying degrees. When leaf primordia-free shoot apical meristems (LP-free SAMs) were cultured after bombardment, vigorous shoots failed to develop from the wounded SAM; instead, the wounded LP-free SAMs regenerated a SAM by repairing the wounded areas and developed a non-vigorous single shoot. It was concluded the vigorous shoots do not participate in transgenic plant production because vigorous shoots arise from unbombarded lateral meristems. Finally, an effective and versatile method for transgenic plant production was established by combining micro-wound treatment on a SAM by bombardment and LP-free SAM culture to suppress the growth of vigorous lateral shoots after wounding.

Sorbitol Dehydrogenase Gene Expression and Enzyme Activity in Apple: Tissue Specificity during Bud Development and Response to Rootstock Vigor and Growth Manipulation

Sorbitol is the primary photosynthate and translocated carbohydrate in apple (Malus ×domestica), and most of it is converted to fructose by sorbitol dehydrogenase (SDH) in sink tissues. We studied the expression of nine SDH genes, SDH activity, and sorbitol content of apple 1) in buds and floral tissues from dormancy to bloom, 2) in leaves and shoot tips of trees on two rootstocks, the moderately vigorous ‘Malling Merton 111’ (MM.111) and the dwarfing ‘Malling 9’ (M.9), and 3) in shoot tips in response to application of prohexadione-Ca to suppress shoot growth and defoliation and girdling (D/G) to deprive the shoot tip of sorbitol. In mature, orchard-grown trees, sorbitol was the main soluble carbohydrate in expressed xylem sap from dormancy to bloom at levels over 3- to 6-fold those of glucose and fructose, the other major sugars present. Sorbitol levels there increased from dormancy to its highest concentration at the half inch green stage and declined by bloom, while those of the other sugars increased. SDH activity per milligram of protein increased over 4-fold from dormancy to flowering. Three of the nine known SDH genes (SDH1, SDH2, and SDH3) were expressed in immature and mature leaves and all buds from dormancy to bloom, as well as in all floral organs, except that only SDH3 transcript was found in stamen tissue. Two genes, SDH6 and SDH9, were floral-tissue specific; SDH6 transcript was detected in all floral organs except stamens at full bloom, and SDH9 was only expressed in anthers with pollen. In buds and leaves of young, container-grown trees, SDH1 and SDH2 generally accounted for the majority of total SDH expression. There were generally no effects of rootstock on SDH expression, SDH activity, or sorbitol concentration in leaves, while apical shoot tips on M.9 rootstock exhibited greater SDH activity than those on MM.111 or lateral shoot tips on either rootstock, though SDH expression of apical and lateral shoot tips on M.9 was lower than on MM.111. Prohexadione-Ca reduced apical but not lateral shoot growth, increased apical but not lateral shoot tip sorbitol content, had no effect on SDH activity, and increased SDH1 expression of all shoot tips. D/G treatment reduced shoot growth, sorbitol content, and SDH activity, but increased SDH1 expression of apical shoot tips only and SDH2 expression of lateral shoot tips only. This work indicates that sorbitol and other sugars are abundantly available from dormancy to bloom, that SDH activity increased during this period, and that SDH expression is at least in part developmentally regulated within the individual floral and leaf tissues. In shoot tips and leaves of young trees, SDH transcript level was not correlated with sorbitol availability or SDH activity, suggesting that other factors have significant regulatory effects after SDH expression on SDH activity.

Hot Water Treatment Released Endodormancy but Reduced Number of Flowers in Potted Red Raspberry Plants

Partially released dormancy causes poor and uneven bud break in temperate plant species like red raspberry (Rubus idaeus L.). Insufficient chilling may be a problem when raspberries are grown at southern latitudes and in year-round production. Dormancy may be released by sublethal stress in many species. We studied the effect of sublethal stress on endodormancy in red raspberry ‘Glen Ample’ and ‘Ottawa’. Canes growing in pots were treated with either hot water (45 °C, 1 h) or the dormancy-breaking chemical, hydrogen cyanamide (1.04%), after accumulation of 0, 240, 480, 720, 960, or 1200 h of chilling at 1 °C. Bud break, vegetative growth, and number of flowers were recorded during 12 weeks of greenhouse forcing after the treatments. Chilling increased bud break, growth, and dry weight of lateral shoots and number of flowers in both cultivars. During deepest endodormancy (0 and 240 h of chilling), treatment with either hot water or hydrogen cyanamide enhanced bud break and lateral shoot growth but could not completely replace chilling. In ‘Ottawa’, hydrogen cyanamide was more effective than hot water during deepest endodormancy, but hot water treatment broke dormancy effectively when 720 h of chilling had accumulated. For ‘Glen Ample’, hot water was as effective as hydrogen cyanamide in breaking endodormancy. Hot water treatment reduced the number of flowers in ‘Glen Ample’ during late endodormancy (720, 960, and 1200 h of chilling). The chilling requirement for ‘Ottawa’ was fulfilled between 720 and 960 h of chilling. However, in ‘Glen Ample’, 1200 h of chilling was not enough to fully release bud dormancy; bud break remained low and it was increased by dormancy-breaking treatments. Hot water treatment can be used to release endodormancy in raspberries, but treatment conditions need to be optimized to preserve crop potential. Chemical name used: hydrogen cyanamide (Dormex, Hi-Cane, Morgrapes).

THE INFLUENCE OF MICROBIC PREPARATIONS ON FRUIT TRANSPLANTS GROWTH AND DEVELOPMENT

The test data of field experiments on different microbial preparations use at cultivation of peach and sweet cherry transplants in fruit nursery wereshown. Thenumberofthemicrobialpreparationsdeveloped at The Southern Experimental Station of Institute of Agricultural Microbiology UAAS containing active stains of the microorganisms capable to associative nitrogen fixation, phosphorus mobilization, and possessing growth promoting and bioprotektive action were investigated. It was established, that all tested microbial preparations had a positive influence on growth and development of peach and sweet-cherries seedlings at organic nitrogen (manure) background. The greatest transplants output was received in variants with Azotobacterin and Phosphoenterin. Application of Azotobacterin, Phosphoenterin and a complex of microbial preparations at cultivation of a peach on a background of manure had raised the quality and an output of 1-year transplants on 2-10 % due to amplification of plant growth, better grafted maintenance, stimulation of growth and development of lateral shoots and roots of transplants. On a background of mineral nitrogen the positive action of microbial preparations was not observed.

Nitrogen and Substrate Assessment For Pot-in-Pot Production in the Intermountain West

Abstract We investigated optimum nitrogen rates and different growth substrates for short-term finish production of container and bare root shade tree liners in a pot-in-pot production system in the Intermountain West. In one study, nitrogen ranging from 0–27 g N-tree−1 (0–36 lbs N·1000 ft−2) as urea was applied to quaking aspen (Populus tremuloides), ‘Autumn Blaze’ maple (Acer × freemannii ‘Autumn Blaze’), ‘Chanticleer’ flowering pear (Pyrus calleryana ‘Chanticleer’), and ‘Canada Red’ chokecherry (Prunus virginiana ‘Canada Red’). Twenty-six liter liners (#7 container) were transplanted into 57 liter (#15) containers in a retail nursery finishing pot-in-pot system. Trunk diameter growth and shoot-tip elongation measurements were recorded for one growing season. Overall, only pear had a consistent increase in terminal shoot and trunk growth in response to N at 9 g N·tree−1 (12 lbs N·1000 ft−2). Maple and chokecherry exhibited modest lateral shoot growth at 4.5 and 18 g N·tree−1 (10–24 lbs N·1000 ft−2), and aspen growth had no response to N. The second study evaluated the effect of nitrogen rates and substrate type on first-year trunk diameter growth of bare root common chokecherry (Prunus virginiana) and Aristocrat flowering pear (Pyrus calleryana ‘Aristocrat’). Large bare-root liners were installed into a finishing pot-in-pot system with three substrate treatments, a proprietary, a commercial mix using several organic matter sources, and a simple composted bark-pumice mix. Five nitrogen rates, 0–9 g N·tree−1, (0–12 lbs N·1000 ft−2) were applied to each substrate. Pear again had a modest increase in trunk growth at 2.2 g N per tree, but had no response to the different growth substrates. Chokecherry trunk growth did not increase with nitrogen nor did substrate treatment substantively affect growth. This study indicates that Intermountain West retail nurseries can likely reduce first-year nitrogen applications to container and bare root liner stock during finish production, and use a simpler media to achieve optimum growth at potentially lower cost.