The Effect of Temperature on the Production and Abscission of Flowers and Pods in Snap Bean (Phaseolus vulgaris L.)

The effect of temperature on production and abscission of flowerbuds, flowers and pods was studied in a determinate snap-beancultivar (cv. Tenderette). Under moderate temperature (e.g.27/17°C) the onset of pod development was associated withcessation of flower bud production and with enhanced abscissionof flower buds. Raising night temperature from 17°C to 27°Cstrongly reduced pod production, mature pod size and seeds perpod, while an increase in day temperature from 22°C to 32°Chad smaller and less consistent effects. Pod production underhigh night temperature was not constrained by flower productionsince 27°C at night promoted branching and flower bud appearance.Under 32/27°C day/night temperature the large reductionin pod set was due to enhanced abscission of flower buds, flowersand young pods ( 3 cm). Flowers had the highest relative abscissionfollowed by young pods and flower buds. Therefore, the onsetof anthesis and of pod development were the plant stages mostsensitive to night temperature. Pods larger than 3 cm did notabscise but usually aborted and shrivelled under high nighttemperature. The effects of 32/27°C were not due to transientwater stresses and were observed even under continuous irrigationand mist-spraying. High temperature, flower production, pod set, seed set, abscission, snap bean, Phaseolus vulgaris L, Tenderette     

Partitioning of [14C]sucrose and Acid Invertase Activity in Reproductive Organs of Pepper Plants in Relation to Their Abscission Under Heat Stress

The effect of heat stress on processes related to carbohydratepartitioning was investigated in young bell pepper (Capsicumannum L. cv. Maor) plants in relation to abscission of theirreproductive organs at different stages of development. None of the reproductive organs abscised after 5 d in a normalday/night temperature regime (25/18°C). With a temperatureregime of 35°C day, 25°C night, abscission occurredin only a small portion of the flower buds and none of the flowersand fruitlets. However, when temperatures in the day and nightwere reversed (25/35°C, day/night) all the buds and someof the flowers abscised during that time period. The young fruitat the first node did not abscise under any temperature regime.The abscission rate of the flower buds was reduced under heatstress if the developing fruit at the first node had been removed. High temperature during either the light or dark periods reducedthe export of [¹⁴C]sucrose from the source leaf (fed for 48h with [¹⁴C]sucrose). Both heat stress and fruit presence reduced the relative amountof [¹⁴C]sucrose which was exported to the flower buds, flowersand roots. Likewise, these treatments reduced the concentrationof reducing sugars in the reproductive organs. Concomitantly,the heat stress and fruit presence on the first node reducedthe activity of soluble acid invertase in the flower buds andthe roots, but not in young leaves. Overall, the results show that heat stress causes alternationin sucrose distribution in the plant, but may also have specificeffects on metabolic activities related to sucrose import andutilization in flower buds and flowers which in turn may enhancetheir abscission. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acidinvertase, heat stress, reproductive organs, sink leaves. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acid invertase, heat stress, reproductive organs, sink leaves.     

Partitioning of [14C]sucrose and Acid Invertase Activity in Reproductive Organs of Pepper Plants in Relation to Their Abscission Under Heat Stress

The effect of heat stress on processes related to carbohydratepartitioning was investigated in young bell pepper (Capsicumannum L. cv. Maor) plants in relation to abscission of theirreproductive organs at different stages of development. None of the reproductive organs abscised after 5 d in a normalday/night temperature regime (25/18 °C). With a temperatureregime of 35 °C day, 25 °C night, abscission occurredin only a small portion of the flower buds and none of the flowersand fruitlets. However, when temperatures in the day and nightwere reversed (25/35 °C, day/night) all the buds and someof the flowers abscised during that time period. The young fruitat the first node did not abscise under any temperature regime.The abscission rate of the flower buds was reduced under heatstress if the developing fruit at the first node had been removed. High temperature during either the light or dark periods reducedthe export of [¹⁴C]sucrose from the source leaf (fed for 48h with [¹⁴C]sucrose). Both heat stress and fruit presence reduced the relative amountof [¹⁴C]sucrose which was exported to the flower buds, flowersand roots. Likewise, these treatments reduced the concentrationof reducing sugars in the reproductive organs. Concomitantly,the heat stress and fruit presence on the first node reducedthe activity of soluble acid invertase in the flower buds andthe roots, but not in young leaves. Overall, the results show that heat stress causes alternationin sucrose distribution in the plant, but may also have specificeffects on metabolic activities related to sucrose import andutilization in flower buds and flowers which in turn may enhancetheir abscission. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acid invertase, heat stress, reproductive organs, sink leaves     

Periods of Shoot Chilling Sensitivity in Soybean Flower Development, and Compensation in Yield after Chilling

Soybeans [Glycine max (L.) Merr. cv. Ransom] grown at a constant25 °C were placed in a 12-h inductive photoperiod at twoweeks of age. Subgroups were shoot-chilled for one week at aconstant 10 °C during each of the first four weeks of floralinduction. Controls were photoinduced but not chilled. Chillingduring the first week of photoinduction inhibited productionof floral primordia, but did not increase the abscission rateof flowers and pods. Chilling during the second week did notaffect primordium production or abscission rate, but did causea significant increase in numbers of fused and malformed pods.Chilling during the third week caused loss of 77 per cent ofearly flowers and pods by abscission, while fourth week chillingcaused less severe losses by abscission. Inhibition of vegetativegrowth may have been responsible for primordium loss in first-weekplants, while disturbances in the development of flowers wereresponsible for the losses in the other chilling weeks. Althoughchilling during the first and third photoinduction weeks causeda significant reduction in early pod numbers, plants harvestedat 16 weeks of age showed no significant loss in seed yield.Low abscission rates late in pod filling and increased weightof individual seeds compensated for early losses of pods. Thesecompensatory responses to a chilling-induced loss of pods aresimilar to those reported for mechanically depodded soybeans. Glycine max (L.) Merr., soybean, temperature, chilling, floral initiation, anthesis, abscission, yield, compensation     

大豆花荚败育期间的植物激素变化

大豆开花结荚期,不同发育阶段的幼蕾与花荚的脱落率不同,其中以花后5d内的幼荚脱落最严重。与败育花荚相比,正常花荚中的干物质积累量均较高。细胞分裂素(DHZRs,ZRs,iPA)含量也较高,花后3～5d的幼荚中表现更明显。脱落酸(ABA)则是以败育幼蕾及花后3～5d的幼荚中含量较高。不同发育阶段的大豆生殖器官中,正常开放花中的玉米赤霉烯酮(ZEN)含量最高。     

大豆花荚败育期间的植物激素变化

大豆开花结荚期,不同发育阶段的幼蕾与花荚的脱落率不同,其中以花后５ｄ内的幼荚脱落最严重。与败育花荚相比,正常花荚中的干物质积累量均较高。细胞分裂素（ＤＨＺＲｓ,ＺＲｓ,ｉＰＡ）含量也较高,花后３～５ｄ的幼荚中表现更明显。脱落酸（ＡＢＡ）则是以败育幼蕾及花后３～５ｄ的幼荚中含量较高。不同发育阶段的大豆生殖器官中,正常开放花中的玉米赤霉烯酮（ＺＥＮ）含量最高     

Factors affecting the Abscission of Reproductive Organs in Yellow Lupms (Lupinus luteus L.): II. THE EFFECTS OF GROWTH SUBSTANCES, DEFOLIATION, AND REMOVAL OF LATERAL GROWTH

Abscission of flowers in Lupinus luteus L. (var. Weiko II) withoutgrowth of ovaries is followed by abscission of small pods (15–20mm. long). Normally flower abscission is much more pronouncedthan pod abscission. Abscission was delayed on plants from which laterals or theirterminal and axifliary buds were removed. Flower abscissionwas not affected, but pod abscission increased as a result ofdefoliation. When flowers at the base of the main inflorescence were replacedby auxins and anti-auxins flower abscission was induced in eitheran auxin pattern in which most of the flowers near the siteof application dropped, and pods developed on the apical whorls,or an anti-auxin pattern in which pods developed on basal whorlsnear the site of application but not higher up. The anti-auxinpattern was similar to the pattern of abscission normally inducedby developing pods on basal whorls. -Naphthylacetic acid (NAA) was much more effective in inducingabscission than ß-indolylacetic acid (IAA). 2:3:5-triiodobenzoicacid (TIBA), NAA, and IAA applied in mixtures at various concentrationsacted mainly antagonistically, i.e. the abscission-inducingeffect of NAA and LAA was depressed in basal whorls, and inapical whorls the effect of TIBA was less prevalent. Consequentlythe effect of the mixtures on the total number of pods was aboutequal to that of the most active component by itself. All growth substances seemed to move much more efficiently inacropetal direction than in basipetal direction in the flowerstalk. Transport in lateral direction was very limited. The effect of growth substances applied on laterals was enhancedby defoliating the main 8tem. The influence of assimilates on flower and pod abscission andtransport of growth substances is discussed.     

Density Studies on Lupins: I. Flower Development

In an August-sown experiment the pattern of flower developmentwas followed for cv. Ultra (Lupinus albus L.) and cv. Unicrop(L. angustifolius L.) grown at low (10 plants m^–2) andhigh (93 and 83 plants m^–2, Ultra and Unicrop respectively)densities. Dry weight increase of flowers on the main-stem inflorescenceand first lateral below the main-stem were compared at differentfloral stages. Maximum flower weight was reached just priorto the open flower stage and remained constant or declined untila pod formed or abscission occurred. The time period betweenmaximum flower weight and pod formation or abscission was upto 10 days. Emergence of the inflorescence was earlier and thefirst flower of Ultra opened 10 days before Unicrop. Developmentof each terminal raceme (inflorescence) was acropetal, withpods having formed on lower flower nodes when terminal flowerswere still quite immature. Laterals forming the next generationof inflorescences grew from axillary leaf buds below an inflorescencewhile it was in full flower. Sources of competition from connectedreproductive and vegetative metabolic sinks are discussed. Lupinus spp., lupins, flower development, planting density     

Development of Oilseed Rape Buds, Flowers, and Pods In Vitro

A technique for growing buds, flowers, and pods of oilseed rape(Brassica napus L. cv. Haplona) on stem explants in vitro hasbeen developed. Open flowers and young pods underwent normaldevelopment on a basal medium of minerals, vitamins, and sucrosebut the development of buds was less successful. Young buds(3 mm long) did not develop and only limited development ofthe older buds (5 mm long) took place. Some 3 mm-long buds wereinduced to develop to open flowers by adding naphthyl aceticacid or gibberellic acid. Pod and seed set in open flowers werenot affected by adding plant growth substances to the medium,but pod elongation and pod dry weight were promoted by gibberellicacid, 105 M, and benzyl amino purine, 10⁷ M, respectively. Reducingthe supply of sucrose or minerals to open flowers reduced seedset, pod elongation and pod weight but did not affect pod set.The physiological significance of the results is discussed. Key words: In vitro cultures, oilseed rape, pod development, flower development     

Effects of Irradiance and Temperature on Flowering of Chrysanthemum morifolium Ramat. in Continuous Light

The short-day plant Chrysanthemum morifolium cv. Polaris initiatedflower buds in all irradiances of continuous light from 7.5to 120 W m^–2. As the irradiance increased, the transitionto reproductive development began earlier and the number ofleaves initiated before the flower bud was reduced. The autumn-floweringcultivars Polaris and Bright Golden Anne, and the summer-floweringGolden Stardust were also grown in continuous light at differenttemperatures; all initiated flower buds at temperatures from10 to 28 °C but only the buds of Golden Stardust developedto anthesis and then only at 10 and 16°C. Flower initiationbegan earliest at 16–22 °C, and the number of leavesformed before the flower bud was increased at 28°C. GoldenStardust was exceptional in that the number of leaves formedwas also increased at 10 °C. Axillary meristems adjacentto the terminal meristem initiated flower buds rapidly at 10°C but not at 28 °C in all three cultivars. These resultsare discussed in relation to the autonomous induction of flowerinitiation and the effects of the natural environment on floweringof chrysanthemum. Chrysanthemum morifolium Ramat, flowering, irradiance, temperature     

High Temperature Induced Male and Female Sterility in Canola (Brassica napus L.)

Male and female sterility was induced in canola or rapeseed(Brassica napus L. cv. Westar) flowers grown under high temperatureconditions (32°C/26°C; day/night). At maturity, themajority of flower buds remained closed but had protruding stigmas.The stamens were reduced in size and the anthers showed abnormalmicrosporogenesis. The gynoecia, although normal in appearance,did not set seed and ovule development was aberrant. Flowersof the ogu CMS line of B. napus also showed similar ovular abnormalitiesunder high temperatures and male fertility was not restoredin them. The observations presented suggest that high temperaturesin the field may adversely affect the yield of canola. Temperature, male and female sterility, rapeseed, canola, Brassica napus     

Changes of Carbohydrates in Pepper (Capsicum annuum L.) Flowers in Relation to Their Abscission Under Different Shading Regimes

Abscission of pepper flowers is enhanced under conditions oflow light and high temperature. Our study shows that pepperflowers accumulate assimilates, particularly in the ovary, duringthe day time, and accumulate starch, which is then metabolizedin the subsequent dark period. With the exception of the petals,the ovary contains the highest total amounts of sugars and starch,compared with other flower parts and contains the highest totalactivity, as well as activity calculated on fresh mass basis,of sucrose synthase, in accordance with the role of this enzymein starch biosynthesis. Low light intensity or leaf removaldecreased sugar accumulation in the flower and subsequentlycaused flower abscission. The threshold of light intensity fordaily sugar accumulation in the sink leaves was much lower thanin flowers, resulting in higher daytime accumulation of sugarsin the sink leaves than in the adjacent flower buds under anylight intensity, suggesting a competition for assimilates betweenthese organs. Flowers of bell pepper cv. ‘Maor’and ‘899’ (sensitive to abscission) accumulatedless soluble sugars and starch under shade than the flowersof bell pepper cv. ‘Mazurka’ and of paprika cv.‘Lehava’ (less sensitive). The results suggest thatthe flower capacity to accumulate sugars and starch during theday is an important factor in determining flower retention andfruit set. Pepper; Capsicum annuum L.; abscission; shading; pepper flowers; ovary; leaves; sugars; starch; acid invertase; sucrose synthase     

Effects of Diazocyclopentadiene (DACP) and Silver Thiosulphate (STS) on Ethylene Regulated Abscission of Sweet Pea Flowers (Lathyrus odoratus L.)

The ethylene production rate of cut sweet pea flower buds increased37-fold during the first 48 h of their vase life. This increasein ethylene production was accompanied by petal wilting at 72h and abscission of the buds 24 h later. Exposure of the cutspikes to the ethylene action inhibitor diazocyclopentadiene(DACP, 170 µI 1^-1) for 18 h under fluorescent lights delayedsubsequent wilting and abscission and promoted bud opening.Silver thiosulphate (0·2 mM) was more effective thanDACP, delaying wilting for longer and preventing abscissionentirely.Copyright 1995, 1999 Academic Press Ethylene, abscission, silver thiosulphate, diazocyclopentadiene, flower senescence, wilting, sweet pea, Lathyrus odoratus L     

Heat Stress-induced Abortion of Buds and Flowers in Pea: Is Sensitivity Linked to Organ Age or to Relations between Reproductive Organs?

A short period of heat stress can cause a significant increasein abortion frequency of floral buds and flowers in pea, buta large variability in sensitivity exists among reproductiveorgans (ROs) within a plant or between plants. We have analysedspatial distribution of abortion frequency in plants subjectedor not subjected to heat stress in: (1) four controlled environmentexperiments in which apex temperature was increased to 31 °Cfor 6 h per day for 4 d (moderate stress); (2) one field experimentwith a similar level of stress; and (3) one experiment with2 d with 33/30 °C day/night (severe stress) in additionto treatment (1). Influence of neighbouring organs on sensitivityto heat stress was analysed by partial flower removal. Severeheat stress caused rapid interruption of RO development followedby abscission while, in moderate stress, at leat 4 d elapsedbetween cessation of stress and first symptoms of abortion.In both moderate stress and control treatments, abortion frequencyfollowed a consistent pattern along the stem with no abortionon the lowest reproductive phytomeres, a temperature-dependentabortion frequency on intermediate phytomeres and 100% abortionon apical phytomeres. Regardless of temperature, this patternwas shifted by four positions if ROs were removed on the lowestfour reproductive phytomeres, and no abortion was observed ifyoung pods were sequentially removed. Moderate heat stress increasedthe effect of developing ROs on abortion frequency of youngerROs located above them. We suggest that the effect of mild stressshould be viewed as the acceleration of a programme linked tothe normal termination of phytomere production during the plantcycle, rather than as an abrupt event linked to stress. Pisum sativum; heat stress; abortion; abscission; age; organ-to-organ relations     

Density Studies on Lupins. II. Components of Seed Yield

Components of seed yield of cv. Ultra (Lupinus albus L.) andcv. Unicrop (L. angustifolius L.) were measured when grown atthree densities. The low density (10 plants m^–2) Unicropyield (34 g seed per plant) was 1.8 times that of Ultra as ithad more branches, pods and seeds per pod. Ultra seeds (310mg per seed) were heavier than Unicrop seeds (180 mg). The branchingpattern of Ultra was less dependent on plant density, henceat 93 plants m^–2 it gave a higher per plant yield (7.4vs 6.4 g) than Unicrop at lower densities (83 plants m^–2).Density had most influence on pod formation and only small effectson seeds per pod and seed weight. Yield components on the main-steminflorescence were influenced less by density than componentson branch inflorescences. Later formed, higher order generationsof inflorescences were most affected by increased inter- andintra-plant competition. Pod numbers on the main-stem were similarfor both species. Pods formed at higher flower nodes in Unicrop,but the lower flower nodes were less fertile than those in Ultra.Node position of flowers had no influence on seed set in main-stemUnicrop pods, but pods from higher nodes in Ultra formed fewerseeds. Seed weights in Unicrop were similar among main-stemnodes but in Ultra seed weights tended to increase at highernodes. Lupinus spp, lupins, seed yield, planting density     

Ethylene perception inhibitor 1-MCP decreases oxidative damage of leaves through enhanced antioxidant defense mechanisms in soybean plants grown under high temperature stress

Ethylene is a stress hormone involved in early senescence and abscission of vegetative and reproductive organs under stress conditions. Ethylene perception inhibitors can minimize the impact of ethylene-mediated stress. The effects of high temperature (HT) stress during flowering on ethylene production rate in leaf, flower and pod and the effects of ethylene inhibitor on ethylene production rate, oxidative damage and physiology of soybean are not understood. We hypothesize that HT stress induces ethylene production, which causes premature leaf senescence and flower and pod abscission, and that application of the ethylene perception inhibitor 1-Methyl cyclopropene (1-MCP) can minimize HT stress induced ethylene response in soybean. The objectives of this study were to (1) determine whether ethylene is produced in HT stress; (2) quantify the effects of HT stress and 1-MCP application on oxidative injury; and (3) evaluate the efficacy of 1-MCP at minimizing HT-stress-induced leaf senescence and flower abscission. Soybean plants were exposed to HT (38/28 °C) or optimum temperature (OT; 28/18 °C) for 14 d at flowering stage (R2). Plants at each temperature were treated with 1-MCP (1 μg L⁻¹) gas for 5 h or left untreated (control). High temperature stress increased rate of ethylene production in leaves, flowers and pods, production of reactive oxygen species (ROS), membrane damage, and total soluble carbohydrate content in leaves and decreased photosynthetic rate, sucrose content, F_v/F_m ratio and antioxidant enzyme activities compared with OT. Foliar spray of 1-MCP decreased rate of ethylene production and ROS and leaf senescence traits but enhanced antioxidant enzyme activities (e.g. superoxide dismutase and catalase). In conclusion, HT stress increased ethylene production rates, caused oxidative damage, decreased antioxidant enzyme activity, caused premature leaf senescence, increased flower abscission and decreased pod set percentage. Application of 1-MCP lowered ethylene and ROS production, enhanced antioxidant enzyme activity, increased membrane stability, delayed leaf senescence, decreased flower abscission and increased pod set percentage. The beneficial effects of 1-MCP were greater under HT stress compared to OT in terms of decreased ethylene production, decreased ROS production, increased antioxidant protection, decreased flower abscission and increased pod set percentage.     

Interactive effects of high temperature and elevated carbon dioxide concentration on cowpea [Vigna unguiculata (L.) Walp.]

Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive failure under heat stress. Heat stress affects two stages of reproductive development in cowpea [Vigna unguiculata (L.) Walp.], and genotypes are available with tolerance and sensitivity to heat during these different stages. The objectives of this study were to determine the responses of these cowpea lines to ambient and elevated [CO₂], under heat stress and optimal temperature, and test whether differences in carbohydrate supplies due to genotypes, CO₂ enrichment and heat stress are associated with differences in sensitivity to heat during reproductive development. Plants were grown in reach-in growth chambers and subjected to day/night temperatures of either 33/20 or 33/30°C, and [CO₂] levels of either 350 or 700 μmol mol^-1. Under intermediate night temperature (33/20°C), all lines set substantial numbers of pods. Under high night temperature (33/30°C) with either ambient or elevated [CO₂], one heat-sensitive line produced no flowers and the other set no pods, whereas the heat-tolerant line abundantly set pods. High night temperature reduced the overall carbohydrate content of the plants, especially peduncle sugars, and caused decreases in photosynthetic rates. The high pod set of the heat-tolerant line, under high night temperature, was associated with higher levels of sugars in peduncles compared with the heat-sensitive lines. The heat-tolerant line accumulated substantial shoot biomass, exhibited less accumulation of starch in leaves, and possibly had less down-regulation of photosynthesis in response to CO₂ enrichment and heat stress than the heat-sensitive lines. Elevated [CO₂] resulted in higher overall carbohydrate levels in heat-sensitive lines (starch in leaves, stems and peduncles), but it did not increase their heat tolerance with respect to flower production or pod set. Heat-induced damage to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles, indicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat-tolerant line was the most responsive genotype to elevated [CO₂] with respect to pod production under either high or intermediate temperatures.     

The Effect of Fruit Load, Defoliation and Night Temperature on the Morphology of Pepper Flowers and on Fruit Shape

The shape and regularity of bell pepper (Capsicum annuumL.)fruit are known to be determined at a very early stage of flowerdevelopment. Small, flattened fruit which are commonly parthenocarpicdevelop under low-temperatures (below 16 °C) from flowerswith enlarged ovaries. In such flowers self-pollination is notefficient because of the large distance between the stigma andstamens. Flower deformation of this kind is common during thewinter season. In the present study it was found that deformationsof flowers, similar to those found under low temperatures, wereinduced in 15 d by complete removal of fruit from plants growingunder night-time temperatures of 18 °C. Only flowers whichwere at the pre-anthesis stage at the time of fruit removalwere deformed by this treatment. Removal of leaves from thelower part of the plant (source leaves) partially reduced theeffect of fruit removal on the shape of the flowers and on subsequentfruit morphology. Fruit removal induced significant increasesin the concentrations of starch and reducing sugars, but notsucrose, in the flower buds. Likewise, flower buds of plantswhich grew under a night-time temperature of 12 °C containedmore carbohydrate than those which grew at 18 °C. Theseresults suggest that flower morphology in pepper is at leastpartly controlled by source-sink relationships. Assimilateswhich are normally transferred to developing fruit may be transported,upon fruit removal, to the flower buds which subsequently swell.A similar increase in assimilate translocation to flower budsmay occur under low temperatures, subsequently causing deformationof fruit.Copyright 1999 Annals of Botany Company Pepper, (Capsicum annuumL), flower shape, low temperatures, source-sink relationship, fruit shape, seeds, reducing sugars, sucrose, starch.     

Influence of Water Stress on Flowering and Seed Production of Macroptilium atropurpureum cv. Siratro

Macroptilium atropurpureum cv. Siratro was grown in large soilbeds with a constant water table below, developing a dawn leafwatêr potential of --0.25 MPa. Water stresses equivalentto -0.7 or -1.0 MPa were developed over 14 d, causing reducedstem and bud elongation, leaf expansion, and bud differentiationand survival. Apex size, the proportion of buds which were floralor vegetative, the early phases of floral initiation, and seedformation on advanced inflorescences were little affected duringthe water deficit period. Upon rewatering previously stressed plants showed increasesrelative to control plants in the rates of shoot appearance,leaf expansion and new node appearance. The ratio of buds becomingfloral was independent of watering treatment, and the enhancedrate of floral bud production in the previously-stressed treatmentswas due to higher rates of total bud differentiation which persistedfor up to six weeks after rewatering. Survival of floral budswas reduced by previous stress, but number of flowers per inflorescence,pod setting, seed number per pod and 100-seed weight were independentof treatment. Seed production was controlled by inflorescencedensity. Rate of seed production was independent of treatmentduring water deficit and four weeks subsequently, and was thenenhanced by 46 and 54 per cent relative to the control in the–0.7 and –1.0 MPa treatments respectively. Macroptilium atropurpureum, Siratro, floral initiation, flowering, seed production, water stress, bud development     

Physiological Responses of Cut Rose Flowers to Exposure to Low Temperature: Changes in Membrane Permeability and Ethylene Production

Senescence of cut rose flowers (Rosa hybrida L. cv. Mercedes)at 22 °C occurred earlier in flowers previously held at2 °C for 10 d or 17 d than in freshly cut flowers. Thisadvanced senescence was observed as an earlier increase in bothethylene production rate and membrane permeability. The risein ethylene production preceded the rise in the level of ionleakage from petals, and this in turn preceded visible symptomsof petal death. Applied ethylene stimulated ion leakage andinhibitors of ethylene synthesis and action (amino-oxyaceticacid and silver thiosulphate respectively) inhibited the normalincrease in ion leakage. The maximum rate of ethylene productionof 22 °C increased markedly in petals of flowers previouslyheld at 2 °C, up to nine times the level in fresh flowers.We conclude that during exposure of rose flowers to 2 °C,in addition to senescence, processes were induced which ledto stimulated ethylene production after transferral to 22 °C.Ethylene apparently caused the subsequent advance in membranepermeability and senescence. Key words: Rose flower, Low temperature, Senescence