Shoot Growth Cessation Research Articles

Identifying indicators of apple bud dormancy status by exposure to artificial forcing conditions.

Dormancy in temperate fruit trees is a mechanism of temporary growth suspension, which is vital for tree survival during winter. Studies on this phenomenon frequently employ scientific methods that aim to detect the timing of dormancy release. Dormancy release occurs when trees have been exposed to sufficient chill, allowing them to resume growth under conducive conditions. This study investigates dormancy dynamics in two apple (Malus × domestica Borkh.) cultivars, 'Nicoter' and 'Topaz', by sampling branches in an orchard over 14weeks (2019 to 2020) and over 31weeks (2021 to 2022) and subjecting them to a 42-day budbreak forcing period in a growth chamber. Temporal changes in budbreak percentages demonstrated dormancy progression in the studied apple cultivars and allowed the three main dormancy phases to be distinguished: paradormancy (summer dormancy), endodormancy (deep dormancy) and ecodormancy (spring dormancy), along with transition periods between them. Using these data, we explored the suitability of several alternative methods to determine endodormancy release. Tabuenca's test, which predicts dormancy release based on the differences in dry weights of buds with and without forcing, showed promise for this purpose. However, our data indicated a need for considerable adjustments and validation of this test. Bud weight and water content of buds in the orchard did not align with budbreak percentages under forcing conditions, rendering them unsuitable for determining endodormancy release in 'Nicoter' and 'Topaz'. Shoot growth cessation did not seem to be connected with either dormancy progression or dormancy depth of the studied cultivars, whereas leaf fall coincided with the beginning of the transition from endo- to ecodormancy. This work addresses methodological limitations in dormancy research and suggests considering the mean time to budbreak and budbreak synchrony as additional criteria to assess tree dormancy status.

A simple and cost-effective method for studying anoxia tolerance in plants.

We developed a novel, cost-effective protocol that facilitates testing anoxia tolerance in plants without access to specialized equipment. Arabidopsis thaliana and barley (Hordeum vulgare) seedlings were treated in airtight 2-L Kilner jars. An anoxic atmosphere was generated using Oxoid AnaeroGen 2.5-L sachets placed on in-house, custom-built wire stands. The performed experiments confirmed a higher sensitivity to low oxygen stress previously observed in anac017 A. thaliana mutants and the positive effect of exogenous sucrose on anoxia tolerance reported by previous studies in A. thaliana. Barley seedlings displayed typical responses to anoxia treatment, including shoot growth cessation and the induction of marker genes for anaerobic metabolism and ethylene biosynthesis in root tissue. The results validate the novel method as an inexpensive, simple alternative for testing anoxia tolerance in plants, where access to an anaerobic workstation is not possible. The novel protocol requires minimum investment and is easily adaptable.

Цифровое сканирование роста и развития древесных растений

The paper presents a photometric device and a procedure for quickly recording the characteristics of organs or parts of woody plants during their growth in the field conditions with maximum detail and accuracy. The procedure was tested in the study of seasonal dynamics of Viburnum lantana L. introduced in Middle Taiga and a species of local flora V. opulus L. The research results show that there are differences in the species seasonal dynamics rhythm associated with the influence of the current and previous environmental conditions. Air temperature explains the greatest dependence of the beginning of growth and the majority of phenodates. It was found that early beginning and end of vegetation is typical for V. opulus. The growth and development of the introduced V. lantana occur in a warmer environment. Shoots of V. opulus begin to grow on May 18–21, after 11 days growth is observed in V. lantana. The earliest terms of shoot growth cessation were found in V. opulus (June 19); V. lantana shoot growth ends 7 days later. The longest shoots of the current year (101 mm) were formed in V. lantana, which is 26 mm longer than in V. opulus. The beginning of shoots growth in V. opulus is observed at +4.7 °C average daily air temperature and the sum of positive temperatures 187 °C, in V. lantana this process begins at +8.8 °C and 308 °C, respectively, and the species requires 6 days with average daily temperature above +10 °C to start growing. Thus, the studied Viburnum species can be conditionally divided into 2 groups: early (V. opulus) and late (V. lantana) beginning and ending seasonal development. Cultivated in the taiga zone V. lantana belongs to the highly promising introduced species, so it can be recommended for introduction into cultural cenoses and landscaping of settlements in the taiga zone. Acknowledgments: The research was supported by the Karelia Innovation Business Startup MVP within the framework of the Program for Support of Applied Research and Development of Students and Postgraduate Students of the Petrozavodsk State University. For citation: Kabonen A.V., Gavrilova O.I., Kishchenko I.T. Digital Scanning of Woody Plant Growth and Development. Lesnoy Zhurnal = Russian Forestry Journal, 2022, no. 6, pp. 55–70. (In Russ.). https://doi.org/10.37482/0536-1036-2022-6-55-70

Adaptive performance of genetically improved and unimproved seedlings of Scots pine

Our main objective was to determine whether various genetically improved reproductive materials of Scots pine ( L.) differ in growth rhythm, autumn cold acclimation and resilience from unimproved materials. The study consisted of two successive indoor experiments with Scots pine seedlings representing four levels of genetic gain (unimproved natural stands, first-generation seed orchards, 1.5-generation seed orchards and seed orchards established with freezing-tested parents) and a wide range of geographical origins within Finland. The seedlings were assessed for terminal shoot elongation, growth cessation, bud set, freezing injuries and bud flushing over the first growth period. All the adaptive traits showed a latitudinal trend regardless of the genetic level. Seed orchard progenies and natural stand progenies did not differ significantly in the timing of growth cessation, bud set, and the flushing rate of the frost-injured seedlings, after the trait variation was adjusted to the latitude of origin. The differences in autumn frost hardiness were insignificant, too, except for the somewhat higher injury rate displayed by the first-generation seed orchard materials. The finding was not conclusive due to ambiguous results from the two experiments. Overall, we did not find evidence of alarming compromises in the adaptive performance of genetically improved materials.Pinus sylvestris

Growth and development of the introduced Fraxinus L. species in the taiga zone (Karelia)

Most species of woody plants indigenous to the Russian taiga are extremely sensitive to pollutants. However, many species of deciduous trees that grow in other geographical areas, including the genus Fraxinus, are fairly tolerant to progressive environmental pollution. For the introduction of cultivated plants into new environmental conditions, an impartial assessment of their introduction potential is required, which is possible only on the basis of comprehensive studies. The most important processes characterising the condition of plants are growth and development. The present study examined the introduction of three species of the Fraxinus L. genus to the middle taiga subzone. These were F. excelsior L., F. americana L. and F. pennsylvanica Marsh. The stems and leaves of the plants were measured once every 2–3 days over the course of two growth periods. Phenological observations were carried out between May and October over the course of 17 years. The introduction potential of the studied species was determined through visual assessment carried out in the autumn. The findings showed that the growth of shoots and leaves in the studied Fraxinus species began in late May-early June, varying between species by 1–5 days. The cessation of shoot and leaf growth in the studied Fraxinus species, which occurred in July, varied by up to ten days. The dates of onset and culmination of the growth of shoots and leaves appeared to be determined primarily by air temperature, with a year-by-year variability of 3–7 days. All the studied Fraxinus species showed a high degree of introduction potential and can be successfully used for gardening and landscaping purposes in the middle taiga subzone.

Palissage Reduces Cluster Zone Lateral Shoots Compared to Hedging

Summary Goals: Hedging grapevines is a common canopy management practice in vineyards in the northeastern United States, however it is criticized as being a short-term solution to vine vigor because it can stimulate lateral shoot growth, resulting in a repeated cycle of hedging and leaf removal that costs growers time and money. Palissage is an alternative canopy management tool where long shoot tips are tucked down into the canopy (i.e. Tuck) or wrapped horizontally along the top of the canopy (i.e. Wrap). Anecdotally, growers had reported that palissage initiated earlier cessation of shoot growth during the growing season and reduced or eliminated the need for leaf removal in the fruiting zone due to fewer lateral shoots. This work aimed to test the effects of palissage on vegetative and reproductive growth, yield, disease incidence and severity, and juice and wine sensory on Riesling ( Vitis vinifera L.) grown in northeastern United States. Key Findings Neither palissage treatment affected vine yield in 2015, but Tuck increased yield in 2016 compared to hedging. Wrap reduced the number of laterals in the fruit zone in 2015 but not 2016 compared to hedging. Tuck increased rachis length by 1.4 cm compared to hedging in 2016, but cluster compactness wasn’t reduced by either treatment. Tuck and Wrap decreased botrytis incidence slightly in 2016 when compared to hedging. A sensory panel found that wines grouped separately by treatment based on aroma. Impact and Significance: This study demonstrated that palissage – particularly Wrap - was a potentially viable canopy management technique to reduce lateral growth in the fruit zone. Impacts varied based on year, but in at least one year palissage reduced lateral shoot growth in the fruiting zone, increased rachis length, and maintained or increased yield, although fruit in the Tuck treatment was less ripe. The potential long-term impacts palissage has on vine vigor, yield, and fruit quality need to be further explored, but these methods hold promise to break the hedging-leaf removal cycle in vigorous vineyards.

Phloem Girdling of Norway Spruce Alters Quantity and Quality of Wood Formation in Roots Particularly Under Drought.

Carbon (C) availability plays an essential role in tree growth and wood formation. We evaluated the hypothesis that a decrease in C availability (i) triggers mobilization of C reserves in the coarse roots of Picea abies to maintain growth and (ii) causes modification of wood structure notably under drought. The 6-year-old saplings were subjected to two levels of soil moisture (watered versus drought conditions) and root C status was manipulated by physically blocking phloem transport in the stem at three girdling dates (GDs). Stem girdling was done before the onset of bud break [day of the year (doy) 77], during vigorous aboveground shoot and radial stem growth (GD doy 138), and after cessation of shoot growth (GD doy 190). The effect of blockage of C transport on root growth, root phenology, and wood anatomical traits [cell lumen diameter (CLD) and cell wall thickness (CWT)] in earlywood (EW) and latewood (LW) was determined. To evaluate changes in belowground C status caused by girdling, non-structural carbohydrates (soluble sugars and starch) in coarse roots were determined at the time of girdling and after the growing season. Although fine root mass significantly decreased in response to blockage of phloem C transport, the phenology of root elongation growth was not affected. Surprisingly, radial root growth and CLD of EW tracheids in coarse roots were strikingly increased in drought-stressed trees, when girdling occurred before bud break or during aboveground stem growth. In watered trees, the growth response to girdling was less distinct, but the CWT of EW significantly increased. Starch reserves in the roots of girdled trees significantly decreased in both soil moisture treatments and at all GDs. We conclude that (i) radial growth and wood development in coarse roots of P. abies saplings are not only dependent on current photosynthates, and (ii) blockage of phloem transport induces physiological changes that outweigh drought effects imposed on root cambial activity and cell differentiation.

Effects of nitrogen-supply levels on leaf senescence and characteristics of distribution and utilization of 13C and 15N in Fuji 3 apple grafted on different stocks

Two-year-old potted Fuji 3 apple trees on different rootstocks [Fuji 3/M. micromalus Makin (joe), Fuji 3/M7 (semi-dwarf) and Fuji 3/M26/M. micromalus Makin (dwarf)] were used to study leaf morphology and photosynthesis and the characteristics of distribution and utilization of 13C and 15N at different nitrogen supply levels (0N, 25%N and 100%N, the N content in 100% N treatment was the same as that in Hoagland complete nutrient solution) under sand culture condition. The main results were as follows: At shoot growth cessation stage in autumn, the leaf chlorophyll content (SPAD), leaf nitrogen content and photosynthetic rate were found the highest in Fuji 3/M. micromalus Makin, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments (0N and 25%N), however, under normal nitrogen treatment (100%N) Fuji 3/M26/M. micromalus Makin had the highest leaf SPAD value, photosynthetic rate and the nitrogen content, followed by Fuji 3/M7, and the lowest was found in Fuji 3/M. micromalus Makin. The leaf SOD and CAT activities showed Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin under the same nitrogen stress treatments, but showed Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin under the normal nitrogen treatment. There were significant differences in the distributions of 15N and 13C in root and leaf in the 3 scion-stock combinations, and the distribution rates of 15N and 13C in roots were the highest under nitrogen stress treatments and in the order of Fuji 3/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M26/M. micromalus Makin. The distribution rates of 15N and 13C in leaves were the highest under the normal nitrogen treatment and in the order of Fuji 3/M26/M. micromalus Makin > Fuji 3/M7 > Fuji 3/M. micromalus Makin. The 15N utilization ratio differed significantly among the 3 scion-stock combinations under different nitrogen application levels and was in the order of Fuji 3/M. micromalus Makin (44.3%, 37.5% and 31.4%)> Fuji 3/M7 (38.8%,30.7% and 26.6%) > Fuji 3/M26/M. micromalus Makin (32.0%,27.2% and 22.5%).

Effects of soil temperature on bud break, shoot and needle growth, and frost hardiness in Pinus sylvestris var. mongolica saplings during dehardening

The present study evaluated the influence of delayed soil thawing on the growth and frost hardiness of Pinus sylvestris var. mongolica saplings between September 2011 and August 2012 in Northern China (41°35′N, 116°32′E). The saplings were randomly divided into three treatments: control, snow removal, and snow removal + insulation. The control saplings were grown under natural conditions. Snow cover was removed from the saplings in the snow removal treatment. For the snow removal + insulation treatment, snow cover was removed and soil surface was covered with a layer of hay (15 cm). The bud break, current-year shoot elongation and diameter as well as current-year needle elongation were measured and compared among the three treatments. The frost hardiness of previous-year stems and needles was assessed using the electrical impedance spectroscopy method. The saplings in the snow removal + insulation treatment exhibited delayed bud break, needle and shoot growth, as well as cessation of needle and shoot growth compared to the other treatments. In contrast, the growth of shoots and needles was generally higher in the snow removal treatment. A linear relationship was observed between plant growth, especially needle elongation, and temperature sum at soil depth of 20 cm. During dehardening, there were no differences in frost hardiness for both stems and needles among the treatments. In conclusion, snow removal + insulation delayed growth, whereas snow removal accelerated the growth. The frost hardiness of saplings during dehardening did not differ among treatments significantly. The possible reduction of snow cover and increase of soil freezing under warming climate would not have negative impacts on saplings in terms of frost hardiness during dehardening. Nevertheless, increased soil freezing would have unfavorable influences in terms of shoot and needle growth.

Modified grape composition under climate change conditions requires adaptations in the vineyard

<p style="text-align: justify;"><strong>Aim:</strong> Major effects of climate change are an increase in temperature, a modification in rainfall patterns and an increase in incoming radiations, in particular UV-Bs. Grapevines are highly sensitive to climatic conditions. Hence, plant development, grape ripening and grape composition at ripeness are modified by climate change. Some of these changes are already visible and will be amplified over the coming decades; other effects, although not yet measurable, can be predicted by modeling. The objective of this paper is to assess which modifications in wine quality and typicity can be expected and what levers growers can implement to adapt to this changing situation. </p><p style="text-align: justify;"><strong>Methods and results:</strong> This paper focusses on the effect of temperature, vine water status and UV-B radiation in viticulture. Vine phenology is driven by temperacture. A significant advance in phenology (i.e. budburst, flowering and veraison dates) has been observed since the early 1980’s in most winegrowing regions. The combined effect of advanced phenology and increased temperatures results in warmer conditions during grape ripening. In these conditions, grapes contain more sugar and less organic acids. Composition in secondary metabolites, and in particular aromas and aroma precursors, is dramatically changed. Increased drought, because of lower summer rain and/or because of higher reference evapotranspiration (ET<sub>0</sub>), induces earlier shoot growth cessation, reduced berry size, increased content in skin phenolic compounds, lower malic acid concentrations and modified aroma and aroma precursor profiles. Increased UV-B radiation enhances the accumulation of skin phenolics and modifies aroma and aroma precursor profiles. Over the next decades, an amplification of these trends is highly likely. Major adaptations can be reached though modifications in plant material (grapevine varieties, clones and root stocks), vineyard management techniques (grapevine architecture, canopy management, harvest dates, vineyard floor management, timing of harvest, irrigation) or site selection (altitude, aspect, soil water holding capacity).</p><p style="text-align: justify;"> <strong>Conclusion:</strong> Climate change will induce changes in grape composition which will modify wine quality and typicity. However, these modifications can be limited through adaptations in the vineyard.</p><p style="text-align: justify;"><strong>Significance and impact of the study:</strong> This study assesses the impact of major climatic parameters (temperature, water and radiation) on vine physiology and grape ripening. It addresses the issue of how the expected changes under climate change will impact viticulture. It is shown that appropriate levers do exist to allow growers to adapt to this new situation. Among these, modifications in plant material and viticultural techniques are the most promising tools.</p><div> </div>

Modified grape composition under climate change conditions requires adaptations in the vineyard

Aim: Major effects of climate change are an increase in temperature, a modification in rainfall patterns and an increase in incoming radiations, in particular UV-Bs. Grapevines are highly sensitive to climatic conditions. Hence, plant development, grape ripening and grape composition at ripeness are modified by climate change. Some of these changes are already visible and will be amplified over the coming decades; other effects, although not yet measurable, can be predicted by modeling. The objective of this paper is to assess which modifications in wine quality and typicity can be expected and what levers growers can implement to adapt to this changing situation. Methods and results: This paper focusses on the effect of temperature, vine water status and UV-B radiation in viticulture. Vine phenology is driven by temperacture. A significant advance in phenology (i.e. budburst, flowering and veraison dates) has been observed since the early 1980’s in most winegrowing regions. The combined effect of advanced phenology and increased temperatures results in warmer conditions during grape ripening. In these conditions, grapes contain more sugar and less organic acids. Composition in secondary metabolites, and in particular aromas and aroma precursors, is dramatically changed. Increased drought, because of lower summer rain and/or because of higher reference evapotranspiration (ET0), induces earlier shoot growth cessation, reduced berry size, increased content in skin phenolic compounds, lower malic acid concentrations and modified aroma and aroma precursor profiles. Increased UV-B radiation enhances the accumulation of skin phenolics and modifies aroma and aroma precursor profiles. Over the next decades, an amplification of these trends is highly likely. Major adaptations can be reached though modifications in plant material (grapevine varieties, clones and root stocks), vineyard management techniques (grapevine architecture, canopy management, harvest dates, vineyard floor management, timing of harvest, irrigation) or site selection (altitude, aspect, soil water holding capacity). Conclusion: Climate change will induce changes in grape composition which will modify wine quality and typicity. However, these modifications can be limited through adaptations in the vineyard.Significance and impact of the study: This study assesses the impact of major climatic parameters (temperature, water and radiation) on vine physiology and grape ripening. It addresses the issue of how the expected changes under climate change will impact viticulture. It is shown that appropriate levers do exist to allow growers to adapt to this new situation. Among these, modifications in plant material and viticultural techniques are the most promising tools.

Effect of exogenous abscisic acid on cold acclimation in two Magnolia species

In northern China, freezing injury is observed frequently in the rare species Magnolia wufengensis but not in the more common species Magnolia denudata. To investigate the role of the phytohormone abscisic acid (ABA) on frost tolerance in these two species, exogenous ABA was applied to the seedlings and then physiological and biochemical responses were measured during cold acclimation. Shoot growth cessation was stimulated by ABA in M. wufengensis but not in M. denudata. Abscisic acid inhibited shoot growth in M. wufengensis but not in M. denudata. Treatment with ABA stimulated leaf senescence in both species, and this effect was greater in M. denudata. For both species, ABA-treated plants exhibited bud dormancy sooner and had an increased tolerance to freezing, decreased water content and increased accumulation of proline, glucose, and fructose in shoots. These effects were generally greater for M. denudata. Freezing tolerance was significantly correlated with content of water, proline, glucose, and fructose for both species, but freezing tolerance was significantly correlated with raffinose content only in M. wufengensis. We conclude that exogenous ABA could increase cold acclimation and improve cold hardiness of both Magnolia species, although M. denudata was more responsive to ABA than M. wufengensis, which might result from a greater dehydration and accumulation of proline and certain soluble sugars.

Endogenous rhythmic growth in oak trees is regulated by internal clocks rather than resource availability.

Common oak trees display endogenous rhythmic growth with alternating shoot and root flushes. To explore the mechanisms involved, microcuttings of the Quercus robur L. clone DF159 were used for (13)C/(15)N labelling in combination with RNA sequencing (RNASeq) transcript profiling of shoots and roots. The effect of plant internal resource availability on the rhythmic growth of the cuttings was tested through inoculation with the ectomycorrhizal fungus Piloderma croceum. Shoot and root flushes were related to parallel shifts in above- and below-ground C and, to a lesser extent, N allocation. Increased plant internal resource availability by P. croceum inoculation with enhanced plant growth affected neither the rhythmic growth nor the associated resource allocation patterns. Two shifts in transcript abundance were identified during root and shoot growth cessation, and most concerned genes were down-regulated. Inoculation with P. croceum suppressed these transcript shifts in roots, but not in shoots. To identify core processes governing the rhythmic growth, functions [Gene Ontology (GO) terms] of the genes differentially expressed during the growth cessation in both leaves and roots of non-inoculated plants and leaves of P. croceum-inoculated plants were examined. Besides genes related to resource acquisition and cell development, which might reflect rather than trigger rhythmic growth, genes involved in signalling and/or regulated by the circadian clock were identified. The results indicate that rhythmic growth involves dramatic oscillations in plant metabolism and gene regulation between below- and above-ground parts. Ectomycorrhizal symbiosis may play a previously unsuspected role in smoothing these oscillations without modifying the rhythmic growth pattern.

Physiological and Biochemical Processes of Magnolia wufengensis in Response to Foliar Abscisic Acid Application during Natural Cold Acclimation

The rare species Magnolia wufengensis frequently suffers from freezing injury in northern China. To investigate the influence of exogenous abscisic acid (ABA) application on the natural cold acclimation of M. wufengensis, physiological and biochemical changes in field-grown M. wufengensis seedlings subjected to foliar ABA treatments at four concentrations (0, 300, 600, and 900 mg·L−1) were evaluated from Sept. 2012 to Jan. 2013. The optimum foliar application concentrations of ABA for M. wufengensis were between 600 and 900 mg·L−1, which led to faster shoot growth cessation, leaf senescence, and development rates of bud endodormancy level and shoot freezing tolerance. The improved freezing tolerance under exogenous ABA application was associated with promoted dehydration and accumulation of proline, soluble protein, and certain soluble sugars such as glucose and fructose. Foliar ABA treatments initiated a cascade of steps for advancing the cold acclimation process of M. wufengensis. We suggest that exogenous ABA application may be used on M. wufengensis grown in northern China, where there are short growing seasons and early fall frost events.

Inflorescence Bud Initiation, Development, and Bloom in Two Southern Highbush Blueberry Cultivars

Blueberry (Vaccinium spp.) production is increasing worldwide, particularly in subtropical growing regions, but information on timing and extent of inflorescence bud development during summer and fall and effects on bloom the next season are limited. The objectives of this study were to determine time of inflorescence bud initiation, describe internal inflorescence bud development, and determine the relationship between internal inflorescence bud development and bloom period the next spring in two southern highbush blueberry [SHB (Vaccinium corymbosum interspecific hybrids)] cultivars. ‘Emerald’ and ‘Jewel’ SHB buds were collected beginning in late summer until shoot growth cessation in late fall for dissection and identification of organ development. Inflorescence bud frequency and number, vegetative and inflorescence bud length and width throughout development, and bloom were also assessed. Inflorescence bud initiation occurred earlier in ‘Emerald’ compared with ‘Jewel’. Five stages of internal inflorescence bud development were defined throughout fall in both cultivars, ranging from a vegetative meristem to early expansion of the inflorescence bud in late fall. ‘Emerald’ inflorescence buds were larger and bloomed earlier, reflecting the earlier inflorescence bud initiation and development. Although inflorescence bud initiation occurred earlier in ‘Emerald’ compared with ‘Jewel’, the pattern of development was not different. Timing of inflorescence bud initiation influenced timing of bloom with earlier initiation resulting in earlier bloom.

Shoot growth of Merlot and Cabernet Sauvignon grapevine varieties

The objective of this work was to evaluate shoot growth of the grapevine varieties Merlot and Cabernet Sauvignon, during 2006/2007, and Cabernet Sauvignon, during 2008/2009, in São Joaquim, SC, Brazil. The experiment was carried out in a commercial vineyard trained on a vertical trellis system. The shoots of the central part of the plants were selected, and the lengths from the base to the apex of 20 shoots per cultivar were evaluated. In 2006/2007, monitoring began at pruning, on 9/15/2006, and ended on 2/6/2007, totalizing 144 days of evaluation. During the 2008/2009 cycle, phenology and shoot growth for 'Cabernet Sauvignon' were assessed from grape development (1/13/2009) (pea-sized grapes) until shoot vegetative growth had ceased. Budburst occurred in the second half of September, and shoot-growth cessation occurred during ripening. Higher growth rates (about 4 cm per day) were observed in pre- and post-flowering, followed by reduction due to the competition for photosynthates for the formation of flowers and bunches. Temperature and photoperiod induce grapevine shoots to cease growth in the highland regions of Santa Catarina State, Brazil.

Molecular dissection of an adaptive epigenetic memory mechanism in norway spruce

Molecular dissection of an adaptive epigenetic memory mechanism in norway spruce

Foliar Application of Abscisic Acid Induces Dormancy Responses in Greenhouse-grown Grapevines

The purpose of this study was to investigate the influence of foliar application of abscisic acid (ABA) on grapevine dormancy, specifically to: 1) determine the optimum foliar application concentration of ABA and 2) evaluate the morphological and physiological changes of greenhouse-grown grapevines in response to exogenous ABA application. Vitis vinifera ‘Cabernet Franc’ and Vitis spp. ‘Chambourcin’ with different leaf ages (40, 50, 80, 100, 110, and 120 days) were subjected to foliar ABA application at different concentrations (0, 100, 200, 400, 600, 800, 1600, and 3200 mg·L−1) and to a cold-acclimated regime. Concentrations of 800 mg·L−1 or higher were phytotoxic and the optimum concentrations were between 400 and 600 mg·L−1. Optimum concentrations of ABA inhibited shoot growth and advanced growth cessation, periderm formation, and leaf senescence, which led to advanced dormancy in both cultivars. In this study, it was concluded that exogenous ABA induced endodormancy because single cuttings (not paradormant) under favorable growing conditions (not ecodormant) were used. Furthermore, grapevine response to ABA was influenced by leaf age and cold treatment. ABA was effective in inhibiting shoot growth and increasing periderm formation in the young vines with 40- to 50-day old leaves and the old grapevines with 80- to 120-day old leaves. However, ABA was effective in inducing early shoot cessation, leaf senescence and abscission, and dormancy in old vines with 100- to 120-day old leaves only. The advanced morphological and physiological changes induced by exogenous ABA mimicked those triggered by environmental cues during the cold acclimation process. It was suggested that advancing the cold acclimation process using foliar ABA application may be beneficial for long-season grape cultivars grown in regions with short growing seasons and early fall frost events.

PREFERENTIAL AMMONIUM UPTAKE DURING GROWTH CYCLE AND IDENTIFICATION OF AMMONIUM TRANSPORTER GENES IN YOUNG PEAR TREES

Five sequences showing homology with gene coding for ammonium (NH+ 4 ) transporters of the subfamily AMT1 (AMT1 genes) involved in the nitrogen (N) uptake process were identified in 2-year-old ‘Rocha’ pear/BA29 through reverse transcription polymerase chain reaction (RT-PCR) analysis. Multiple AMT1 genes were expressed in each phase of the growth cycle and results suggest that ammonium uptake is conducted by several transporters expressed simultaneously. Trees grown in pots received 2 g N tree−1, at dates corresponding to active shoot vegetative growth, shoot growth cessation and beginning of leaf fall, in the form of either ammonium nitrate (NH 15 4 NO3) or 15NH4NO3. N was preferentially absorbed as NH+ 4 at all sampling dates, ranging from 62% to 66% of the total labelled N recovered in the trees. The fertilizer N use efficiency was also higher for ammonium treatment than for nitrate treatment at all sampling dates. N uptake rate and preferential NH+ 4-N absorption were not altered in response to root pruning and gibberellic acid (GA3) treatments.

Rootstock-induced dwarfing in cherries is caused by differential cessation of terminal meristem growth and is triggered by rootstock-specific gene regulation

Use of dwarfing rootstocks has dramatically increased the profitability of fruit production by reducing production costs, reduced chemical use and higher density plantings. Despite the importance of rootstock-induced dwarfing, the cause of this phenomenon is not known. Using two commercially available graft combinations consisting of a sweet cherry scion, 'Bing', on a dwarfing rootstock (Gi5) or a semi-vigorous rootstock (Gi6), we discovered that the difference in grafted tree height was due to a significantly earlier cessation of terminal meristem growth of the scion on Gi5 compared to Gi6 rootstock, rather than shorter metamer length. We then carried out cDNA-AFLP analysis to investigate differential gene expression between the two graft combinations. Transcript-derived fragments (TDFs) identified as differentially expressed were cloned and printed on microarrays for further confirmation of the differential expression. A total of 99 TDFs were identified as differentially expressed between the 'Bing'/Gi5 and 'Bing'/Gi6 samples, including genes involved in transcription regulation, brassinosteroid signaling, flavonoid metabolism and cell wall biosynthesis or modification. Rootstock vigor has a significant effect on gene expression at the scion and the graft union. Timing of the differential gene expression in the dwarf trees coincides with the earlier cessation of terminal shoot growth, suggesting that these differentially expressed genes may be involved in the dwarfing phenomenon.