Changes of Respiration Rate, Ethylene Evolution, and Abscisic Acid Content in Developing Inflorescence and Young Fruit of Olive (Olea europaea L. cv. Konservolia)

Simultaneous measurements of respiration, ethylene production, and abscisic acid (ABA) concentrations, as well as the growth parameters length, fresh weight (FW), and dry weight (DW) of olive (Olea europaea L. cv. Konservolia) inflorescence were carried out at short intervals (3–7 days) during the period from bud burst until the 3rd week after full bloom (AFB), when young fruit reached 8 mm in length. The axis of inflorescence elongated remarkably during the 3rd week after bud burst (ABB), massive bract shedding occurred during the 4th week ABB, full bloom (FB) was observed 7 weeks ABB, and massive floral organ abscission 1 week AFB. The results showed a continuous increase in inflorescence FW and DW from bud burst until 4 days before FB. Respiration rate, ethylene production, and levels of ABA were relatively high during the first 3 weeks ABB. After this period, respiration and ethylene followed a similar pattern of changes, inversely to that of ABA concentration. An accumulation of inflorescence ABA 6 and 4 days before FB was associated with the minimum values of respiration and ethylene production on the same dates. The sharp decrease in the ABA concentration during FB and 3 days later was followed by a high rise in ethylene and an increase in respiration rate, which both rose further 1 week AFB. The results suggest a possible correlation of ABA with the early stage of floral abscission, whereas ethylene production seems to be correlated with the terminal separatory activity in olive inflorescence abscission processes. Received May 28, 1998; accepted November 17, 1998     

Effects of ethylene and 1-MCP (1-methylcyclopropene) on bud and flower drop in mini <Emphasis Type="Italic">Phalaenopsis</Emphasis> cultivars

Phalaenopsis frequently exhibits bud drop during production and in response to adverse postharvest conditions. The effect of exogenous ethylene on bud drop of mini Phalaenopsis was studied and ethylene sensitivity of four cultivars was compared. Water content, membrane permeability and ABA (abscisic acid) content in floral buds and flowers were determined after ethylene treatment. Exogenous ethylene induced flower bud drop in all tested Phalaenopsis cultivars and the different cultivars showed distinct differences in ethylene sensitivity. The cultivar Sogo ‘Vivien’ exhibited the highest bud drop, water loss and change in membrane permeability in floral petals, while Sogo ‘Berry’ showed the lowest sensitivity. The ethylene inhibitor 1-MCP (1-methylcyclopropene) reduced ethylene-induced floral bud drop in the cultivar Sogo ‘Yenlin’. ABA content in floral buds was increased in response to ethylene and 1-MCP pretreatment inhibited the ethylene-induced increase in ABA levels efficiently. This finding suggests that the observed increase in ABA content during bud drop was mediated by ethylene. The interaction between ABA and ethylene is discussed.     

The effect of drought hardening and chilling on ABA content in xylem sap and ABA - delivery rate from root of tomato plant

This paper is a continuation of our studies related to the response of two tomato cultivars: Robin and New Yorker to chilling: the later is more tolerant to chilling than the former one (Starck et al. 1994). The concentration of ABA in the xylem sap and ABA delivery rate (calculated as the amount of ABA exuded in 2h from the cut stump, following shoot removal) were estimated by ELISA. The relative water content (RWC) of the leaf blades and stomatal resistance (RS) were also measured. Tomato plants were grown in a greenhouse, under noncontrolled conditions. Before chilling some of the plants were drought hardened for 10 days (H). As an consequence of water deficit only New Yorker growth slightly decreased. Plants were chilled to 2–5 °C during three consecutive, 16-h nights, preceded by warm days, which caused a decrease in the RWC of leaf blades. Chilling did not decreased leaf blade hydration significantly, but drastically increased the concentration of ABA in the xylem sap in more chilling tolerant cv. New Yorker only. The delivery rate of ABA was markedly enhanced in both cultivars, but much more in New Yorker. Drought hardening increased ABA delivery rate in cv. Robin only, especially after chilling. The lack of correlation between changes in the RWC of leaf blades after low temperature treatment and the concentration of ABA in the xylem sap as well as its delivery rate suggest, that in both tomato cultivars chilling increased ABA level directly, not as an secondery effect of temperature-induced water deficit.     

The effect of LAB 173711 and ethephon on time of flowering and cold hardiness of peach flower buds

Peach flowers are often killed during bloom by spring frosts. LAB 173711, a compound with abscisic (ABA)-like activity, and ethephon delayed flowering in peach trees. In greenhouse experiments, LAB 173711, at concentrations of 10^–3–10^–2 M, was most effective in delaying bloom when applied after a 5°C cold storage period, rather than before the dormancy breaking treatment. In contrast, ethephon delayed bloom most effectively when applied before 5°C cold storage; ethephon caused flower bud abscission when treatments were made after the chilling requirement had been satisfied. In field experiments, ethephon delayed flowering by 6–7 days, which reduced bud injury after a spring frost during bloom. No flower bud injury was found on ethephon-treated trees after temperatures of –4.3°C; whereas without ethephon 25% of the flower buds were frost damaged. LAB 173711 delayed the time to 50% bloom by 2–3 days. However, this was not long enough to avoid low-temperature injury to the flower buds.     

Abscisic acid relationships in the chill-related dormancy mechanism in apple seeds

Abscisic acid (ABA) levels in seeds from three cultivars of apple (Malus domestica Borkh.) which have substantially different chilling requirements were investigated by gas chromatography mass-spectrometry selected ion monitoring (GCMS-SIM) during stratification. The ABA content of dormant unchilled seeds was similar in the three cultivars, suggesting no relationship between the chilling requirement of those seeds and their ABA status. That chilling is not related to ABA changes during stratification was confirmed by warm (20°C) and cold (5°C) stratification experiments. ABA content dropped rapidly and nearly identically under both temperature regimes, but only cold stratification promoted germination. The decline in ABA during stratification was due in large part to leaching from the seed coat and nucellar membrane; the ABA content of the embryo remained nearly constant. The radicle in intact seeds stratified at 5°C began growing 20–30 days after the ABA in the seed coat and nucellar membrane had nearly disappeared. Radicle growth did not occur in unchilled seeds, even though ABA had leached from them as well. It is possible that the leaching of ABA from the seed allows certain promotive forces to develop, but if so, these can develop only at chilling temperatures. Studies were also conducted on 2-trans ABA relationships to apple seed dormancy, but no association was evident.Report No. 12, Department of Fruit and Vegetable Science, Cornell University.     

Bud Dormancy in the Kiwi Fruit, Actinidia chinensis Planch

A study of lateral bud dormancy in Actinidia chinensis has shownthat true dormancy can be induced, especially in short daysat warm and constant temperatures This dormancy can be brokenquantitatively by chilling but temperatures as high as 10 °Care effective The dormancy appears to be due to an inhibitor(possibly ABA), apparently stored in the special bud cover aspecial structure in Kiwi fruit which may represent fused stipulesRemoval of the cover also admits oxygen and light, both of whichhave promoting effects on bud break Application of ABA enhancesdormancy (as do crude extracts tentatively identified as ABA)while GA₃ application enhances dormancy before chilling andpromotes bud break only after chilling Actinidia chinensis, Kiwi fruit, dormancy, abscissic acid, gibberellic acid, chilling     

Transcript profiling in Vitis riparia during chilling requirement fulfillment reveals coordination of gene expression patterns with optimized bud break

Endodormant grapevine buds require a period of chilling before they break and begin to grow. Custom Vitis bud cDNA microarrays (9,216 features) were used to examine gene expression patterns in overwintering Vitis riparia buds during 2,000 h of 4°C chilling. Three-node cuttings collected concurrently with buds were monitored to determine dormancy status. Chilling requirement was fulfilled after 1,500 h of chilling; however, 2,000 h of chilling significantly increased the rate of bud break. Microarray analysis identified 1,469 significantly differentially expressed (p value < 0.05) array features when 1,000, 1,500, and 2,000 h of chilling were compared to 500 h of chilling. Functional classification revealed that the majority of genes were involved in metabolism, cell defense/stress response, and genetic information processing. The number of significantly differentially expressed genes increased with chilling hour accumulation. The expression of a group of 130 genes constantly decreased during the chilling period. Up-regulated genes were not detected until the later stages of chilling accumulation. Hierarchical clustering of non-redundant expressed sequence tags revealed inhibition of genes involved in carbohydrate and energy metabolism and activation of genes involved in signaling and cell growth. Clusters with expression patterns associated with increased chilling and bud break were identified, indicating several candidate genes that may serve as indicators of bud chilling requirement fulfillment. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The effect of LAB 173711 and ethephon on time of flowering and cold hardiness of peach flower buds

Peach flowers are often killed during bloom by spring frosts. LAB 173711, a compound with abscisic (ABA)-like activity, and ethephon delayed flowering in peach trees. In greenhouse experiments, LAB 173711, at concentrations of 10^?3–10^?2 M, was most effective in delaying bloom when applied after a 5°C cold storage period, rather than before the dormancy breaking treatment. In contrast, ethephon delayed bloom most effectively when applied before 5°C cold storage; ethephon caused flower bud abscission when treatments were made after the chilling requirement had been satisfied. In field experiments, ethephon delayed flowering by 6–7 days, which reduced bud injury after a spring frost during bloom. No flower bud injury was found on ethephon-treated trees after temperatures of ?4.3°C; whereas without ethephon 25% of the flower buds were frost damaged. LAB 173711 delayed the time to 50% bloom by 2–3 days. However, this was not long enough to avoid low-temperature injury to the flower buds.     

Chilling and heat requirements for the prediction of the beginning of the pollen season of Alnus glutinosa (L.) Gaertner in Ponferrada (León, Spain)

Winter-flowering trees such as the alder (Alnus glutinosa (L.) Gaertner) can survive periods of adverse climatic conditions, entering a period of dormancy in the early fall. The end of dormancy and the start of the pollen season require a period of low temperatures followed by another of warm temperatures. These requirements were studied from 1995 to 2002, in order to develop a model to predict the onset of the alder pollen season in Ponferrada (Spain). Chilling accumulation took place from late October to late December or early January. The best result was obtained with a threshold temperature of 6.5 °C and an average of 848 chilling hours (CH). Heat requirements were calculated at maximum temperature, an average 143 growth degree days (GDD) were needed, with a threshold temperature of 0 °C. In order to validate models, predicted values were compared with real values for 2002–2003, 2003–2004 and 2004–2005, years not used in developing the models. Predictions for the pollen-season start-date differed only slightly from observed dates: in 2002–2003 predicted and observed dates were the same, in 2003–2004 there was a difference of 7 days and in 2004–2005 a difference of 3 days.     

ABA Levels and Effects in Chilled and Hardened Phaseolus vulgaris

Leaf abscisic acid (ABA) levels of chilled P. vulgaris weremeasured after 18 h chilling at 5°C, at a saturation deficitof 1.24 g m^–3 (SD), and after chilling in a water-saturatedatmosphere. Changes were also followed during a chill hardeningperiod of 4 d at 12°C, 2.1 g m^–3 SD. It was foundthat hardening resulted in an almost 5. fold increase in ABAlevels after 3 d at 12°C, and this decreased to approximatelycontrol levels on the fourth day. Subsequent chilling of hardenedplants produced no change in ABA levels from that of controlplants (22° C). In contrast, non-hardened plants chilledat 1.24 g m^–3 SD had ABA levels almost 3 times the levelof control plants. However, chilling in a water-saturated atmosphereresulted in a decrease in ABA levels. In addition, the response of leaf diffusion resistance (LDR)to exogenous ABA fed via the transpiration stream was measuredat 5 ° C and 22° C in hardened and non-hardened plants.Use of tritium-labelled ABA was made to calculate the stomatalsensitivity to ABA. It was found that exogenous ABA caused anincreased in LDR at 22°C in both hardened and non-hardenedplants. However, the sensitivity of the hardened plants to ABAwas greater in terms of rate of closure and amount of ABA requiredto close the stomata. At 5°C, however, ABA caused stomatalopening and the maintainance of open stomata in non-hardenedplants. In hardened plants, ABA caused stomatal closure at 5°C.These results are discussed in relation to the locking-openresponse of chilled P. vulgaris stomata. Key words: Chilling, Stomata, ABA, Phaseolus vulgaris     

Hormonal regulation of flower senescence in roses (<Emphasis Type="Italic">Rosa hybrida</Emphasis> L.)

To elucidate the role of the plant hormones—abscisic acid (ABA) and ethylene during flower senescence in roses, experiments were conducted on two cultivars of cut-roses (Rosa hybrida L.), ‘Grandgala’ and ‘First Red,’ obtained from a commercial grower. An apparent similarity was observed during flower senescence and accumulation of endogenous ABA in petal tissue. Several fold increase in ABA concentration was observed during the later stages of senescence which was found to be associated with a drastic reduction of flower water potential and water uptake. During the later stages of senescence (S5–S6) higher ABA concentration coincides with the elevated concentration of ethylene production. ABA and ethylene both stimulate senescence and are suggested to interact during flower senescence under water limitations.     

Trends in phenology of <Emphasis Type="Italic">Betula pubescens</Emphasis> across the boreal zone in Finland

Timing of plant phenophases is a useful biological indicator which shows how nature responds to the variation in climate. Thus, long phenological observation series help to estimate the impact of changing climate on forest plants. We investigated whether phenological patterns of downy birch Betula pubescens respond to warming climate and whether the intensity of the responses varies among phytogeographical zones. We studied data collected by the Finnish National Phenological Network from 30 observation sites across Finland during 1997–2006. The advancement in the timing of the earliest phenophase, bud burst, ranged from 0.7 days/year in southern boreal zone to 1.4 days/year in middle and northern boreal zones. Timing of bud burst was most clearly dependent on mean May temperatures. The intensity of the response to temperature increased from south to north. The advancement of bud burst resulted into a significant lengthening of the growth period by 1.2–1.6 days per year in northern and middle boreal zones, respectively, whereas the lengthening was not significant in the southern boreal zone. No trend was observed in the timing of autumn phenophases.     

Abscisic Acid-induced chilling tolerance in maize suspension-cultured cells

The induction of chilling tolerance by abscisic acid (ABA) in maize (Zea mays L. cv Black Mexican Sweet) suspension cultured cells was examined. Cell viability during exposure to chilling was estimated by triphenyl tetrazolium chloride reduction immediately after chilling and a filter paper growth assay. Both methods yielded comparable results. Chilling tolerance was induced by transferring 5-day-old cultures (late log phase) to a fresh medium containing ABA (10 to 100 micromolar). The greatest chilling tolerance was achieved with ABA at 100 micromolar. Growth of cells was inhibited at this concentration. After a 7-day exposure to 4°C in the dark, the survival of ABA-treated cells (100 micromolar ABA, 28°C for 24 h in the dark) was sevenfold greater than untreated cells. Effective induction of chilling tolerance was first observed when cells were held at 28°C for 6 hours after adding ABA. No tolerance was induced if the culture was chilled at the inception of ABA treatment. Induction of chilling tolerance was inhibited by cycloheximide. These results indicate that ABA is capable of inducing chilling tolerance when ABA-treated cells are incubated at a warm temperature before exposure to chilling, and this induction requires de novo synthesis of proteins.     

The Effects of Exogenously Applied Abscisic Acid on Bud Burst in Salix spp

When cut stems of three species of Salix were transferred tolong day conditions conducive to growth, the number of budswhich grew within a 4 week period was dependent on various factors,including the species and the position of the buds on the stem.In addition, the removal of leaves from the stems at the startof the experiment resulted in a diminution of the number ofbuds which commenced growth while there was a substantial increaseas spring approached. Abscisic acid (ABA) at 10^–4 M was also capable of depressingbud burst in certain circumstances although this effect diminishedas spring approached. The effect of ABA was also significantlygreater in at least two of the three species if the leaves wereremoved from the stems at the time of transfer to long day conditions. Interactions were also observed between species and harvestdates, bud position and species and bud position and harvestdate. Salix spp, willow, bud burst, abscisic acid     

Maximum Fruit Growth Potential and Seasonal Patterns of Resource Dynamics During Peach Growth

Maximum fruit growth potential, the growth attained by fruitswhen they are grown under optimal environmental conditions inthe presence of a non-limiting supply of resources, was estimatedfor two peach [Prunus persica (L.) Batsch] cultivars that differin the timing of resource demand for reproductive growth. Maximumpotential fruit growth was estimated on trees that were heavilythinned at bloom. On these trees, resource availability exceededresource demand for fruit growth. For both cultivars, the mean dry weights of fruits grown onunthinned trees were approximately half the mean dry weightsof fruits grown on trees that were heavily thinned at bloom,indicating that fruit growth was source-limited on unthinnedtrees. Comparison of the seasonal patterns of relative growthrate of fruits on unthinned and heavily thinned trees indicatedthe source-limited fruit growth occurred during distinct periodsof the growing season. On the early maturing cultivar, source-limitedfruit growth occurred from 300 degree-days after bloom untilharvest (4·5-10 weeks after bloom). On the late maturingcultivar, source-limited fruit growth occurred from 200-900and 1600-1900 degree-days (3·5-12 and 18-20 weeks) afterbloom. Although the final dry weight of fruits on the early maturingcultivar was only half that of fruits on the late maturing cultivar,the potential net sink strength of fruits was significantlyhigher on the early than the late maturing cultivar throughoutthe entire growth period of the early maturing cultivar. Resourceavailability for fruit growth was similar on the early and latematuring cultivars, indicating that selection for early maturingfruits has not changed the patterns of resource availabilityfor fruit growth.Copyright 1995, 1999 Academic Press Maximum fruit growth potential, carbon economy, partitioning, resource availability, resource limitation, source-limited growth, sink activity, sink strength, growth analysis, relative growth rate, Prunus persica (L.) Batsch, peach     

Abscisic Acid and Ethylene Interact in Rice Spikelets in Response to Water Stress During Meiosis

This study investigated whether and how the interaction between abscisic acid (ABA) and ethylene is involved in the regulation of rice (Oryza sativa L.) spikelet sterility when subjected to water stress during meiosis. Two rice cultivars, HA-3 (drought-resistant) and WY-7 (drought-susceptible), were used and subjected to well-watered and water-stressed (WS) treatments during meiosis (15–2 days before heading). Leaf water potentials of both cultivars markedly decreased during the day as a result of the WS treatment, but panicle water potentials remained constant. The percentage of sterile spikelets in WS plants was increased by 49.7% for WJ-7 but only 12.7% for HA-3. ABA, ethylene, and 1-aminocyclopropane-1-carboxylic acid were all enhanced in spikelets by the water stress, but ethylene was enhanced more than ABA in WY-7 when compared with that in HA-3. Spikelet sterility was significantly reduced when ABA or amino-ethoxyvinylglycine, an inhibitor of ethylene synthesis, was applied to the panicles of WS plants at the early meiosis stage. Application of ethephon, an ethylene-releasing agent, or fluridone, an inhibitor of ABA synthesis, had the opposite effect, and sterility was increased. The results suggest that antagonistic interactions between ABA and ethylene may be involved in mediating the effect of water stress on spikelet fertility. A higher ratio of ABA to ethylene would be a physiologic trait of rice adaptation to water stress.     

Bud burst in Norway spruce (Picea abies): preliminary evidence for age-specific rest patterns

This study examines the effect of chilling and photoperiod on rest completion and bud burst in Norway spruce [Picea abies (L.) Karst.] using twigs from both 15-year-old (young trees) and 56-year-old (old trees) trees. The material was transferred between September and May from outdoors to experimental forcing conditions with four different photoperiods. The bud burst percentage of the twigs from young trees generally increased in all photoperiods until the end of the year. After that it decreased until vernal equinox (March 20) and then increased steeply towards spring. This new observation of transient rest completion during autumn suggests that young trees have (I) a transient time window during late autumn when ontogenetic development is possible, and (ii) a secondary rest culminating approximately at the time of vernal equinox. In twigs from old trees the transient rest completion was much weaker as the bud burst percentages generally remained under 20 during autumn and winter. At vernal equinox there were no burst buds in twigs from the old trees in any photoperiod and after that the bud burst percentage increased basically in the same manner as in the young trees. The bud burst percentage of the twigs from young trees was generally higher as the photoperiod increased. However, no evidence for absolute long photoperiod requirement of rest completion was observed.     

Variation in Endogenous Gibberellins,Abscisic Acid,and Carbohydrate Content During the Growth Cycle of Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp., a Tuberous Geophyte

Phenologic changes and variation in the level of endogenous gibberellins (GAs), abscisic acid (ABA), carbohydrate content, and α-amylase activity were examined in colored Zantedeschia spp. cv. Cala Gold. These changes were examined in the primary bud tissues and in the attached tuber tissue during the growth cycle. Dormant tubers were dry-stored at 20°C for 3 months, planted in a phytotron, and grown under 22/16 ± 1°C. Plant development was monitored under continued irrigation until leaf senescence and tuber dormancy. GAs and ABA were extracted from the primary bud tissues, fractionated by HPLC, and analyzed using GC-SIM. Starch, glucose, soluble protein, and α-amylase activity were monitored in the tuber tissue attached to the primary bud. Endogenous changes in GAs and ABA in the primary bud were correlated with endogenous changes in carbohydrate content and α-amylase activity in the attached tuber tissue. These correlations were observed during the rest and the growth periods and were associated with developmental changes in the plant, that is, bud dormancy relaxation, bud growth, and inflorescence differentiation. ABA content decreased and a transient pulse of GA was measured in the primary bud concomitantly with the onset of shoot elongation in dry tubers during storage, before planting. The sharp increase of GAs in the bud preceded inflorescence differentiation as observed in dissected apices by about 15 days, as well as the increase in α-amylase activity in the attached tuber tissue. A steep decrease in starch level was measured in the tuber after planting, concomitantly with massive plant growth. These findings suggest a possible involvement of gibberellin in the initiation of α-amylase activity during dormancy relaxation in colored Zantedeschia and in the autonomous induction of flowering.     

Effect of various exogenous and endogenous factors on microspore embryogenesis in Indian mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czern and Coss)

Summary The influence of donor plant growth environment, microspore development stage, culture media and incubation conditions on microspore embryogenesis was studied in three Indian B. juncea varieties. The donor plants were grown under varying environments: field conditions, controlled conditions, or a combination of the two. The correlation analysis between the bud size and microspore development stage revealed that the bud size is an accurate marker for donor plants grown under controlled conditions, however, the same does not hold true for the field-grown plants. The buds containing late uninucleate microspores collected from plants grown under normal field conditions up to bolting stage and then transferred to controlled environment were observed to be most responsive with genotypic variability ranging from 10 to 35 embryos per Petri dish, irrespective of the other factors. NLN medium containing 13% sucrose was found to be most suitable for induction of embryogenesis The fortification of this medium with activated charcoal, polyvinylpyrrolidone, colchicine, or growth regulators (6-benzylaminopurine and 1-naphthaleneacetic acid) was observed to be antagonistic for microspore embryogenesis, while silver nitrate (10 μM) had a significant synergistic effect. A post-culture high-temperature incubation of microspores at 32.5±1°C for 10–15 d was found most suitable for high-frequency production of microspore embryos. The highest frequency of microspore embryogenesis (78 embryos per Petri dish) was observed from the late uninucleate microspores (contained in bud sizes 3.1–3.5 nm irrespective of genotype) cultured on NLN medium containing 13% sucrose and silver nitrate (10 μM), and incubated at 32.5°C for 10–15 d.