The influence of fruiting on the bud sprouting and flower induction responses to chilling in Citrus

Summary

The effect of chilling temperatures on bud sprouting and flower formation was compared on fruiting and non-fruiting ‘Owari’ satsuma mandarin (Citrus unshiu Marc) trees. On non-fruiting trees, bud dormancy was weak, and a significant proportion of buds were able to sprout at high temperatures without being chilled. Separate effects of low temperatures on bud sprouting and flower induction were demonstrated. On fruiting trees these two effects of low temperatures were also demonstrated on summer-flush buds, but not on older (spring-flush) buds. The spring-flush buds from fruiting trees scarcely sprouted without being chilled. These buds required a longer chilling period for dormancy release than for flower induction, and it was not possible to separate the effect of low temperature on flower induction from the effect on dormancy release. The presence of fruit reduced flower formation by reducing bud sprouting. Furthermore, fruit had a direct inhibitive effect on vernalization which resulted in increased formation of vegetative shoots. The effect of fruit and low temperature on flowering was unrelated to carbohydrate accumulation in the leaves or the roots.     

Molecular characterization of an S-adenosylmethionine decarboxylase gene from floral organ differentiating axillary bud in calamondin (× Citrofortunella mitis)

Summary

Calamondin (× Citrofortunella mitis J. Ingram & H. E. Moore) is known for its ability to develop floral organs to flower in the adult phase during the four seasons. To provide information on molecular events during floral differentiation from axillary buds, we constructed a cDNA library from floral differentiating axillary buds of adult phase calamondin. Ninety-six cDNA clones were randomly selected from this library and sequenced. Ninety-six nonredundant ESTs were identified. Two clones encoded S-adenosylmethione decarboxylase, a key enzymes in polyamine biosynthesis. CmSAMDC 1 (Citrofortunella mitis s-adenosylmethionine decarboxylase 1) contained an 1083 bp ORF that encoded a putative SAMDC precursor of 361 amino acids. Northern blot analysis revealed that CmSAMDC 1 was expressed in axillary buds prior to floral differentiation and in axillary buds immediately after floral differentiation, in immature flower (5 mm), in fully developed flowers (120 mm long), in floral parts (petals, pistils, and stamens) of trees in the adult phase of development, but not in leaves or axillary buds of juvenile phase nucellar seedlings or leaf tissue from trees in adult phase of development. In situ hybridization revealed expression of the CmSAMDC 1 gene in the floral apex of axillary buds after differentiation, and in the phloem of axillary buds and petioles. These results suggest that SAMDC could play a role in actively differentiating and developing reproductive and vegetative organs.     

Effects of NAA and Carbaryl on Fruit Set and Return Bloom for Some Apple (Malus domestica Borkh.) Cultivars

Abstract

This research was conducted in 1997 and 1998 to investigate the effects of naphthalene acetic acid (NAA) (5, 10, and 15 ppm), Carbaryl (1-naphthyl N-methylcarbamate) (750, 1000, and 1250 ppm), and NAA + Carbaryl (5 + 750, 7.5 + 750, and 10 + 750 ppm) applications on the return bloom of some standard apple (Malus domestica Borkh.) cultivars grafted on MM106 rootstock. Of these applications, 750 ppm Carbaryl for ‘Starkspur Golden Delicious’, 1250 ppm Carbaryl for ‘Granny Smith’ and ‘Starkrimson Delicious’, and 5 ppm NAA for ‘Jonagold’ increased the mean number of flower buds significantly, compared with the control treatments. The other treatments of Carbaryl, NAA, and NAA + Carbaryl also increased the mean number of flower buds in a nonsignificant sense with a few exception. A negative correlation between the final fruit set and the mean number of next year's flower buds was found for three cultivars. The correlation coefficients were r = ?0.5150 (P< 0.05), r = ? 0.6999 (P< 0.05), r = ?0.0335 for ‘Starkspur Golden Delicious’, ‘Granny Smith’, and ‘Jonagold’ cultivars, respectively. However, this relationship was positive and nonsignificant for ‘Starkrimson Delicious’ (r = 0.1980).     

Simultaneous down-regulation of DORMANCY-ASSOCIATED MADS-box6 and SOC1 during dormancy release in Japanese apricot (Prunus mume) flower buds

In temperate deciduous fruit crops such as Prunus spp., bud endodormancy is an important physiological phase affecting the timing of blooming and subsequent fruit development. Japanese apricot (Prunus mume) bears unmixed flower buds, separate from vegetative buds, that bloom slightly more than a month before vegetative bud burst. Seasonal expression of Prunus mume DORMANCY ASSOCIATED MADS-box genes (PmDAMs) has previously been analyzed only in vegetative buds, with an association between these genes and flower bud endodormancy release not yet confirmed. In this study, we performed a seasonal expression analysis of PmDAM1–6 genes in flower buds of two Japanese apricot genotypes – namely, high-chill and low-chill cultivars. The analysis revealed that PmDAM3, PmDAM5, and PmDAM6 expressions are closely associated with dormancy release in both flower and vegetative buds. In addition, a yeast two-hybrid screening demonstrated that PmDAM6 can interact in yeast with the homolog of Arabidopsis SOC1 (PmSOC1). Synchronized expression patterns were detected in PmDAM6 and PmSOC1 during dormancy release in flower buds of the two genotypes. Taken together, these results suggest that the dimer of PmDAM6 and PmSOC1 may play a role in the regulation of dormancy transition and blooming time in Japanese apricot flower buds.     

Strawberry fruit yield and quality responses to flower bud removal: A simulation of damage by strawberry blossom weevil (Anthonomus rubi)

Summary

The effect of flower bud severing (with scissors) on the yield and fruit quality of strawberry (cv. Elsanta) grown on raised, polythene-mulched beds varied with plant size and numbers of flower buds per plant. On very small plants (with an average of seven flower buds and yielding 105 g of fruit per plant) severing reduced yield in direct proportion to the proportion of flower buds severed, irrespective of whether severing included or did not include removal of the primary (first node) flower bud. There was no evidence of crop compensation. On larger plants (with 24, 70 and 117 flower buds and yielding 0.34 kg, 0.73 kg and 1.16 kg of fruit per plant respectively) severing up to 12 buds per plant did not significantly affect yield: mean berry weight increased by up to 11% and the percentage fruit (by number) in quality class I increased from 67% to 72% in response to severing. Two mechanisms of yield compensation were, apparent i) an increase in mean berry weight, and ii) the maturing of alternative replacement flower buds. Severing slightly delayed by 1–2 d the date by when 10% and 25% of fruit was picked. Implications for the economic damage threshold for flower bud severing by the strawberry blossom weevil are discussed.     

Reproductive and vegetative bud differentiation in Olea europaea L.

Summary

The apical meristem of cv. Nocellara Etnea buds is described in the course of its anatomical progression, from July until bud break, the following spring. Differences in the apex of potentially vegetative and flower buds are already visible in the summer. In leaf buds the apex is a round dome, with two buttresses determined by leaf primordia. The cells of the outer layers are arranged in concentric rings, distinguished by different conditions of the nucleic acids. In flower buds the apical dome is less prominent, and the outer cell layers are histologically quite uniform. These characteristics remain unchanged in flower buds, and are little modified in leaf buds, until December; in January flower bud differentiation becomes more active, and both bud types start developing with increasing intensity. Our observations postulate a very early anatomical separation of the two bud types, on which further environmental factors might determine the final differentiation process.     

Seasonal variation in the onset and duration of flower development in ‘Royal Gala’ apple buds

Summary

The formation of bud scales, transition leaves, true leaves, bracts and flower primordia were observed in buds removed from non-flowering sites on one year old shoots of apple ‘Royal Gala’. Buds were sampled from trees in Hawke's Bay, New Zealand (latitude 398S) during six successive seasons. The onset of flower development varied between seasons from 72 to 99.d after full bloom. Floral development was poorly synchronized within the populations of sampled buds, lasting 22 to 50.d. Differences in the onset and duration of flower development could not be related to seasonal differences in heat accumulation from full bloom. There was significant variation between seasons in the minimum number of appendages observed within buds that exhibited doming, which indicates floral development. In the 1998/99 season, doming was observed in buds that had only 15.7 appendages, whereas in the 1999/2000 season the minimum number of appendages within a bud that had initiated flowers was 17.5. When the data from all seasons were considered, the rate of appendage formation within developing buds was not consistently related to heat accumulation.     

Anatomical and morphological study of apple (Malus × domesticaBorkh.) flower buds growing under inadequate winter chilling

Summary

Some apples cultivars produce low yields when grown in regions with inadequate winter chilling. Their unsatisfactory development is attributed to the lack of climatic adaptation which causes some abnormalities in bud differentiation. The development of reproductive spurs is erratic, leading to vegetative shoots, and the flower index is very low. The purpose of this work is to understand the flower differentiation problem. An assessment was made through morphological and histological studies, also an analysis of climatic data was performed in an attempt to identify the responsible factors. The number of chilling hours recorded was about 695. Defoliation was delayed and happened during the second week of January. Bud break was advanced by 10 d in comparison with the average period. The spurs density (12 and 23 spurs per m of twigs) was similar to the values observed in normal situation. The buds carried by these spurs evolved into vegetative shoots for all variety × rootstock combination used in this study. The average of this transformation was 47 and 50% for ‘Golden Delicious’ and ‘Starking Delicious’, respectively. A flowering index obtained was very low (1.3 kg per tree). Anatomical observations carried out on buds collected in October showed that differentiation was undertaken and the floral primordium was already formed with some abnormalities in flower development in later stage. At anthesis, internal structures of the buds showed primordia disorganized. Reproductive organs presented pistil abortion with low microsporogenesis. Xylem vessel elements were not observed at the base of the bud and vascular connection was not established. This problem in flower development occurred at this stage which was affected by external factors. The winter was characterized by periods of high temperatures which affect negatively the accumulation of chilling units. The mode of action of temperature, notably of chilling on the formation of flowering organs and vessels, remains to be determined.     

Phenology of strawberry guava (Psidium cattleianum) in ReÂunion Island

Summary

The phenology of wild stands of strawberry guava (Psidium cattleianum Sabine) was studied at 100, 480 and 720.m over 2 years in ReÂunion Island. The shoots bore flower buds at the basal nodes, and vegetative buds at the apical nodes. Trees produced vegetative growth from September to December, flowers from November to January and fruit from February to June. Shoot growth was earlier at 100 and 720.m the first year, but were synchronized in the second year. Flowering and fruiting were also earlier at 100.m. The intervals between shoot emergence and flowering, and flowering and fruit maturity were strongly related to temperature, with base temperatures of 5.58C and 2.68C, and heat units requirements of 675 and 2,5528C.d, respectively. The number of shoots, flowers and fruit per branch varied across sites and years, unrelated to temperature. However, production was significantly higher at 720.m. Production was much lower after a hurricane. Flowering (y) was related to shoot production per branch (x) (log(y)=111.33.log(x); r².=.0.78), whereas the fruit set rate was highly variable between trees (26±100%). The number of fruits per branch (1±6) was possibly related to poor shoot growth or fruit set, but unrelated to the timing of the phenological events. It is expected that commercial orchards would be more productive than feral stands.     

Soil pasteurization and inoculation with Glomus intraradices alters flower production and bulb composition of Zephyranthes spp.

Summary

We assessed whether adding inoculum of the vesicular-arbuscular mycorrhizal fungus (VAMF) Glomus intraradices into growing medium of three Zephyranthes spp (White Rain Lily [WRL], Z. candida; Pink Fairy Lily [PFL], Z. robusta; Yellow Zephyr Lily [YZL], Z. sulphurea) alters aspects of flower and bulb production. Shoots of inoculated plants emerged 7–13 d earlier than those of non-inoculated plants. Inoculation slightly delayed the emergence of flower buds on WRL and PFL, but did not delay the time of flower opening of WRL. Inoculated YZL flowered 4–11.d earlier than non-inoculated plants. The number of flowers produced by YZL was consistently increased by inoculation, while the inoculation with VAMF increased flower production by WRL and PFL only when plants were growing in pasteurized soil. Leaf biomass of inoculated WRL was larger than non-inoculated plants, while leaf biomass was generally smaller in inoculated PFL and YZL. Partitioning of biomass to bulbs and offsets varied with species, soil pasteurization, and inoculation. Inoculation increased the combined weight of bulbs and offsets at the end of the second growing cycle by 50–150%. Inoculated YZL and WRL consistently produced more offsets in the second growing season after inoculation. For all species, inoculation increased phosphorus and carbohydrates and decreased nitrogen and amino acids in bulbs. Adding VAMF into the growing medium of Zephyranthes altered aspects of plant development and biomass partitioning important to flower and bulb production during the first growing cycle after inoculation, and most effects of VAMF inoculation are more pronounced in the second growing cycle after inoculation. Of the three species examined, Z. sulphurea showed the most consistent responses to inoculation.     

Flowering and fruiting phenology,and physico-chemical characteristics of 2-year-old plants of six species of Opuntia from eight regions of Morocco

SUMMARY

We have described the flowering and fruiting phenology of 14 accessions of six Opuntia species grown in Morocco: O. ficus-indica, O. robusta, O. aequatorialis, O. dillenii, O. leucotricha, and O. stricta. We also determined the physicochemical characteristics of their cladodes. For each accession, we used four-to-20 plants. Two systems were used to measure phenology: the extended Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH)-scale and the National Phenology Monitoring System. Five principal stages were described: the development of vegetatively-propagated organs (vegetative buds), the development of flower buds, flowering, fruit development, and fruit maturity. The number of vegetative buds varied significantly among the 14 accessions, while only four accessions produced flower buds. After reaching their final size, fruit lengths varied from 3.40–6.40 cm, while fruit diameters varied from 1.93–3.90 cm. The average cladode number differed significantly among genotypes and varied from 1.75–7.75. There were also significant differences in cladode length (13.75–30.63 cm), width (6.25–17.33 cm), thickness (0.65–1.38 cm), fresh weight (FW; 67.50–766.00 g), and dry weight (DW; 8.75–67.15 g) between species. Water content and ash content, as well as total protein and total sugar concentrations, showed significant differences and were within the ranges of 86.67–92.04% (w/w), 12.97–22.08g 100 g^?1 DW, 4.64–11.56g 100 g^?1 DW, and 3.22–12.51 g 100 g^?1 DW, respectively. Our results will help in the development of agronomic management practices and improve the characterisation, valorisation, and use of cactus pear species grown in Morocco.     

Cover Crops for Fruit Plantations I. Short Term Leys

Summary

The opening of gladiolus florets was accompanied by a substantial increase in fresh and dry weight and carbohydrate content of the perianth. The principal soluble carbohydrate was fructose, with substantially lower concentrations of glucose and sucrose. Although stored carbohydrate, apparently starch, disappeared during floret opening, its contribution to the total carbohydrate content of the open flower was minor. Removal of basal florets from the freshcut spike substantially reduced the dry weight of the opening upper young buds. During development of the inflorescence it appears that there is a transfer of carbohydrate from the senescing lower florets to those developing acropetally.     

Abortion of reproductive organs in sweet pepper (Capsicum annuum L.): a review

Summary

Levels of abortion of reproductive organs (i.e., buds, flowers, and young fruits) in sweet pepper plants (Capsicum annuum L.) are high, and cyclical fluctuations occur in fruit set. Stages susceptible to abortion are very young buds (< 2.5 mm), buds close to anthesis, and flowers and fruits up to 14 d after anthesis. An overview of factors and processes involved in flower and fruit abortion in sweet peppers is presented. More light, higher CO₂ concentrations, and lower planting density, increase the availability of assimilates per plant, and decrease fruit abortion. The cyclical pattern in fruit set is caused by changes in demand for assimilates. High flower abortion occurs when fast growing fruit (at approx. 3 weeks after anthesis) are present, due to competition for assimilates. Fruit set increases when fast growing fruit are almost mature and have a low assimilate demand. Prior to abortion, auxin export from the reproductive organ diminishes, ethylene production increases, and lower levels of activity of sucrose-cleaving enzymes are found. Severe water stress and low nutrient supply also increase abortion levels. Low night- and high day-time temperatures hamper pollen development, causing low seed set, which can result in fruit abortion. Two theories have been used to explain abortion: unbalanced demand for and supply of assimilates, and hormonal dominance of developing fruit over young fruit. Attempts to prevent abortion or to diminish the cyclical pattern of fruit set have not yet been successful, but new suggestions are presented.     

Physiological Breakdown in Stored Monarch Plums

Summary

Several pollination studies carried out on different, self-incompatible almond cultivars and seedlings have shown the presence of variable levels of fruit set following self-pollination that could be attributed to partial self-incompatibility (PSI). PSI is an intermediate reproductive behaviour, described in some angiosperm species, which indicates that self-incompatibility is a quantitative and plastic trait. The present study was performed to substantiate the occurrence of PSI in almond by studying ten cultivars that are traditionally considered to be self-incompatible (four of which had previously shown fruit set after self-pollination). These cultivars were analysed by microscopic observations of the progression of pollen tubes through the pistil following controlled self-pollination, determinations of fruit set after bagging flower buds, and molecular identification of the parentage of the fruits obtained using consensus PCR-primers for Prunus S-RNase alleles. The results showed that, in nearly all cases, the pollen tubes did not enter the ovary and, from a total of 5,349 bagged flower buds, only 17 fruits were obtained. In all cases, PCR analysis of the plants obtained after germination of these seeds showed a band corresponding to an S-RNase allele not present in the maternal progenitor, clearly indicating that they could only have arisen from cross-pollination.Therefore, the low fruit set values observed in some of the cultivars studied were not due to a breakdown in the self-incompatibility response that confers PSI, but to very low rates of contamination with foreign pollen. These results corroborate the self-incompatibility phenotype of the cultivars studied here, and highlight the importance of ascertaining the identity of the parentage in any progeny obtained after bagging.     

Induction of viable 2n pollen in sterile Oriental × Trumpet Lilium hybrids

In order to induce viable 2n pollen from highly sterile diploid Oriental × Trumpet (OT) (Lilium), N₂O was used to treat flower buds of four sterile diploid OT cultivars (‘Nymph’, ‘Gluhwein’, ‘Yelloween’, and ‘Shocking’) at different stages of meiosis. There was no pollen germination in the controls. However, after N₂O treatment at 600 kPa, three of the OT hybrids (‘Nymph’, ‘Gluhwein’, and ‘Yelloween’) not only exhibited fertile flower percentages (4.3–16%), but also higher rates of pollen germination (18.8–72.5%). In addition, both the fertile flower percentages and rates of pollen germination were higher following 48 h N₂O treatment at 600 kPa than the 24 h treatment. Following 72 h N₂O treatment at 600 kPa, most flower buds or plants were damaged and any undamaged flowers showed abnormal anthers at the time of flowering. This indicated that 48 h of N₂O treatment at 600 kPa was optimal to induce viable 2n pollen in three out of four sterile hybrid OT lily cultivars. These results also showed that prophase I – metaphase I was the optimum stage of meiosis at which to induce 2n pollen by N₂O treatment in lily hybrids.     

Vegetative and yield component characteristics of micropropagated muscadine grape (Vitis rotundifolia Michx.)

SUMMARY

Evaluations were made of the field performance of micropropagated (tissue cultured axillary buds) versus conventionally rooted softwood cuttings of muscadine grape, Vitis rotundifolia Michx. Trunk cross-sectional area did not differ between treatments during three years of field evaluation following planting. There were no differences in leaf area and dry weight or shoot number in the two propagation types; leaf morphology was normal with no apparent juvenile characteristics. Yield components including flower number per shoot and inflorescence, fruit number, total fruit weight and yield efficiency were greater in micropropagated plants during the second year, the first year of cropping; differences diminished and yield components were not different in year three. Performance of tissue cultured plants was therefore as good as, or surpassed, conventionally propagated plants during early vine establishment.     

Carbohydrate content of inflorescent buds of defruited and fruiting pistachio (Pistacia vera L) branches in relation to biennial bearing

Summary

Changes in carbohydrate content of inflorescent buds of fruiting and defruited branches of the same tree were measured in 1994 and 1995 in the period before and during bud abscission in pistachio (Pistacia vera L. cv. Aegenes) to investigate its relationship to inflorescent bud abscission. HPLC was used for soluble sugar analysis, while starch was hydrolyzed to glucose enzymatically and the amount of glucose was then determined using the glucose oxidaseperoxidase method. The effect of fruit on leaf net photosynthesis (Pn), chlorophyll a and b (Chl (a+b)) in leaves and specific leaf weight (SLW) was also investigated in 1995. Starch concentration was initially similar in buds of fruiting and defruited branches but became greater in buds of defruited branches from early June 1994 (57 d after full bloom (AFB)) and 20 June 1995 (61 dAFB), resulting in higher starch contents. Glucose and fructose concentrations were similar in flower buds throughout the whole period of measurement; inositol and sucrose (the most abundant sugar in flower buds) both became much lower in fruiting branches from early July 1994 (83 dAFB) and mid July 1995 (88 dAFB). The rapid decrease in sucrose concentration coincided with rapid seed growth and the greatest period of bud abscission in fruiting branches. During the same period, total sugar and total carbohydrate concentrations and contents were greater in buds of defruited branches. The presence of fruit increased Chl (a+b) content in leaves while decreasing SLW between 43 and 61 dAFB. During this same period, leaf Pn rates were greater in fruiting shoots than in defruited ones.