Influence of three contrasted climatic conditions on endodormant vegetative and floral peach buds: analyses of their intrinsic growth capacity and their potential sink strength compared with adjacent tissues

Three treatments with various temperature-photoperiod combinations (LDW: long-day warm; SDW: short-day warm; SDC: short-day cold) were applied to endodormant vegetative and floral peach buds. In order to analyze the effect of these factors on their dormancy state, the following complementary methods were used: (1) for vegetative buds, the ‘single-node cutting' test that measures the growth capacity of the buds connected to the shoot and integrates endo- and short-distance paradormancy; (2) for floral buds, growth rate of the primordia that integrates endo- and all paradormancy. For both kinds of buds: (3) the ‘nucleotides' test that reveals the intrinsic growth capacity of the isolated bud, i.e. endodormancy, by measuring the potential of converting adenosine to non-adenylic nucleotides; (4) the intracellular pH measurement of primordia and adjacent tissues (cushion and shoot) which is supposed to reflect their relative sink strength for nutrients and the competition between them. This is a possible element of short-distance paradormancy.

Temperature, and not photoperiod, strongly determined the evolution of dormancy in vegetative and floral buds. Exposure to temperatures >20°C, prevented the buds recovering any intrinsic growth capacity, but they did it with notable rapidity under 10–18°C temperature regime (SDC). After one month, under all treatments, consistent with the poor chilling effect (nil under LDW and SDW, one third of the normal requirement of chilling units computed with the ‘dynamic' model under SDC), a residual inhibition of the vegetative bud growth was shown to exist at the cutting level. It must be hypothesized as strong short-distance paradormancy. In the floral buds, growth of the primordia started shortly after exposure to SDC conditions. This is possible provided it is assumed that only very weak residual short-distance paradormancy, if any, remained. Intracellular pH values of the studied tissues were influenced by temperature and photoperiod, but the corresponding gradients of the potential sink strength did not fit well with the paradormancy patterns that had been assumed for the vegetative and floral buds, especially under SDC treatment.     

Regulation of flower development in Dendrobium crumenatum by changes in carbohydrate contents,water status and cell wall metabolism

The involvement of carbohydrates, water potential, cell wall components and cell wall-based enzymes in regulating flower development in Dendrobium crumenatum was investigated. Plants were subjected to cold treatment to release floral buds from dormancy, and the various parameters were investigated from young floral bud stage till flower senescence. Development of floral buds was accompanied by progressive decrease in concentrations of fructans and starch. Upon full flower opening, concentration of soluble sugars was maximum, accompanied by a more negative water potential. High pectin methylesterase activity was observed during early bud development and decreased thereafter. Significant increase in activities of β-galactosidase, β-mannosidase and β-xylosidase was also observed during floral bud development. The cell walls of sepals and petals were modified extensively during floral bud and flower development, as observed by changes in the amounts of celluloses, hemicelluloses and total pectin. Pectin solubilisation was also observed to commence during early floral bud development. These results indicated that carbohydrate hydrolysis, osmotic changes and cell wall dissolution that began early in young floral buds, all regulated flower development in this sympodial orchid. Possible applications of the findings in the horticultural industry are discussed.     

Effect of artificial chilling on the depth of endodormancy and vegetative and flower budbreak of peach and nectarine cultivars using excised shoots

Stem cuttings were obtained from 12 peach and nectarine cultivars during leaf fall, placed in plastic bags at 3.0 ± 0.1 °C to simulate 0–800 h of chilling and forced to budbreak at 20.0 ± 1.0 °C for a period of 6 weeks. Some cultivars showed high blooming and leafing without exposure to chilling; chilling enhances leafing and blooming but the percentage increment was higher in leaf buds. In general, maximum budbreak was reached with less chilling accumulation (<100–200 h) in flower buds compared with leaf buds; excessive chilling caused a reduction of the percentage budbreak in flower but not in leaf buds. Additionally, chilling modified the proportion of blooming that occurred before leafing. In non-chilled shoots, blooming occurred earlier than leafing, except in cv. ‘San Pedro 16–33’ but the proportion of blooming before leafing decreased significantly with chilling in most cases. By studying the mean time to budbreak, we conclude that the flower bud generally has a lower intensity of rest; the intensity of rest declines at a slower rate in flower than in leaf buds with chilling; flower buds had greater heat requirements than leaf buds when the chilling requirement had been covered, so that each peach cultivar had a point of critical chilling accumulation below which blooming tended to occur earlier, and above which leafing tends to occur first. Flower and leaf buds had different depths of endodormancy but similar chilling requirements in the majority of peach and nectarine cultivars studied. Finally, different varieties with similar chilling requirements showed different responses to chilling. Therefore, the cutting test measuring the response of vegetative and floral buds provides considerable information on the characterisation of the variety, compared with the sole and traditional data of chilling requirements.     

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.     

Effect of oscillating temperature on the expression of two aquaporin genes (Pp- × TIP1, Pp-PIP2) involved in regulating intercellular water status in flower buds of peach

Summary

We studied the effects of temperature changes on the water status of floral buds in peach during ecodormancy by an analysis of aquaporin (AQP) gene expression and magnetic resonance imaging of the upper part of the bud, the bud base, the bud trace, and the bud cushion. Expression levels of mRNAs of the water channel genes, Pp- TIP1 and Pp-PIP2, in the tonoplast and plasma membrane reflected the temperature oscillations: high temperatures increased mRNA levels and low temperatures decreased them, irrespective of the duration of either treatment.The T₂ relaxation time of the buds, especially in the floral primordia, was significantly longer under oscillating temperature conditions than under a consistently high temperature. The period of high-temperature during the oscillating temperature regime accelerated water flow in the bud, but delayed bud growth. Disruption of the water balance by excessive water in the primordia under oscillating temperatures may be one reason for the delay in bud growth.     

Effects of fruit load on flower bud initiation and development in peach

Summary

This study aims to quantify the effects of fruit crop-load on flowering and to determine the relationships between flowering and phloem sap carbohydrate and nitrogen content fractions from budding to dormancy in ‘Zincal 5’ nectarine. Fruit load significantly reduced the number of flowers per tree both indirectly, by reducing the number of shoots per tree and the number of nodes per shoot, and directly, by reducing the number of floral buds per node. The intensity of the response depended on the number of fruits developed per tree. Trees that kept all fruits up to senescence flowered 35% less than trees thinned by hand to 40% of fruits at pit hardening, and 55% less than trees completely thinned in bloom by hand. Trees that kept all fruits had significantly lower glucose and sorbitol contents in the phloem sap of mixed branches up to harvest date and full vegetative growth, respectively, but no significant relationships were found between the concentrations of these carbohydrates and flowering intensity in the following Spring. Sucrose and fructose did not show any significant difference in regard to crop-load. In fibrous roots, starch content was not related to fruit load up to dormancy, indicating that starch content is not associated with flower bud induction and differentiation. The nitrate-nitrogen fraction was significantly higher, and the ammonium-nitrogen fraction was significantly lower, in trees that tended to flower less, suggesting some disturbance in nitrate reduction in these trees.     

依据显微结构及光合特性探讨蝴蝶兰花芽分化的时期

以蝴蝶兰‘大辣椒’为试验材料,对花芽分化进程及期间光合特性和碳水化合物、可溶性蛋白及激素含量的变化进行研究。结果表明:花芽长度为0、2、4、8、16和24 cm时,分别处于花芽分化初始期、花序原基分化期、花原基分化期、萼片原基分化期和花瓣原基分化期(16和24 cm)。蝴蝶兰叶片的净CO₂吸收速率在花芽发育前期(0～4 cm)没有显著变化,花芽8 cm时显著降低。花芽中的碳水化合物和可溶性蛋白的含量显著高于叶片,碳水化合物在花芽长度为4 cm时达到稳定水平,可溶性蛋白含量在花芽8 cm时达到叶片与花芽的平衡;赤霉素(GA)的含量在花芽2 cm时达到最大值,生长素(IAA)含量在花芽4 cm时显著升高,玉米素(ZT)含量在花芽8 cm时显著降低,而ABA含量在花芽发育的过程中并没有显著变化。由此可知,当蝴蝶兰花芽开始分化萼片原基(8cm)时,光合生理及生化物质基本达到一个相对稳定的水平,此阶段的蝴蝶兰花芽已彻底完成成花分化。     

外源葡萄糖对‘长富2号’苹果花芽生理分化期可溶性糖和相关基因表达的影响

以‘长富2号’苹果为材料,于花后25和30 d喷施浓度1.5%和3%的葡萄糖,研究处理后短枝顶芽的发育状况、可溶性糖、淀粉含量及相关代谢酶活性的动态变化,并利用实时荧光定量PCR检测糖代谢相关基因与成花相关基因的表达模式。结果表明:葡萄糖处理后,短枝顶芽长度、宽度及质量有一定程度增加;短枝顶芽中,蔗糖、葡萄糖、山梨醇在生理分化中前期显著高于对照,淀粉含量整体升高,而果糖含量在整个生理分化期显著降低;山梨醇脱氢酶、山梨醇氧化酶、蔗糖合酶合成方向以及蔗糖磷酸合成酶活性在不同时期有所增加,而酸性与中性蔗糖转化酶,及蔗糖合酶分解方向酶活性普遍降低;叶片中碳水化合物积累明显,糖代谢相关酶活性也发生相似改变;顶芽糖代谢相关基因及2个MdTPS基因都响应葡萄糖处理;成花关键基因MdFT 1、MdFD、MdLFY、MdSOC 1和MdAP 1均显著上调,而成花抑制基因MdTFL 1从花后30 d开始,表达显著下调。     

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.     

草原龙胆( Eustoma grandiflorum )单、重瓣花器官分化的形态学观察

 本篇论文主要研究了草原龙胆单重瓣花器官的发育特征。取花部发生的第1个和第2个花芽为试材, 直接用于实体解剖观察。结果表明: 1. 单瓣花和重瓣花花芽分化过程均可分形态分化前期、萼片原基分化期、花瓣原基分化期、雄蕊原基分化期、雌蕊原基分化期5个时期, 各轮花器官按照向心顺序发育。2. 到雌蕊原基形成为止, 单瓣花花器官各原基的分化过程大约需要12 d, 重瓣花的整个分化过程大约需要15 d。3. 单瓣花和重瓣花都包含5枚萼片、5枚雄蕊和1枚雌蕊, 而单瓣花花瓣是5枚, 重瓣花约是15枚。     

Changes in carbohydrate composition in lettuce flower stalks during development

Summary

Changes in carbohydrate composition in lettuce flower stalks were investigated during growth in order to check whether or not accumulated carbohydrates are used for the rapid development of flower stalks and seed formation. Sucrose was the predominant sugar in lettuce flower stalks, followed by fructans of low molecular weight, glucose and fructose.With regard to fructans, only 1-kestose and 1-nystose were detected, and they increased in concentration from the appearance of terminal flower buds to anthesis. Starch concentration was very low (less than 0.03 mg g^–1 dry weight). The concentrations of sucrose, fructans and hexose decreased during seed formation. If fully-developed lettuce leaves were removed from every other node at the flower bud stage, no significant differences were noted in the concentrations of sucrose, glucose, fructose, and fructans in the flower stalks of defoliated and control plants. These results suggest that sucrose and fructans are reserve carbohydrates in stems, and that accumulated sucrose and fructans are used for seed development.     

103份桃种质在南京地区的需冷量和需热量研究

[目的]用不同模型估算南京资源圃103份桃种质花芽和叶芽的需冷量和需热量,筛选花芽和叶芽需冷量和需热量的最佳估算模型,探讨需冷量、需热量与开花展叶的关系.[方法]连续2 a(年)(2018年11月-2019年4月和2019年11月-2020年4月),采用3种需冷量估算模型和2种需热量估算模型对103份桃种质(南京地区)...     

西瓜3种性型花器官性别分化的细胞形态学观察

以西瓜3种性型(雌雄异花同株系、全雌系和完全花雄花系)的雄花、雌花和完全花3种花芽为材料,制成石蜡切片,进行西瓜花芽不同发育时期的细胞形态学观察。结果表明:西瓜3种性型之间性别分化起始及同种性别之间花器官发育过程并没有明显的形态学差异。雄花、雌花和完全花3种花芽分化首先要经过一个两性期,即雄蕊原基和雌蕊原基同时存在时期,在两性期之前三者不存在明显的形态学差异;当花芽长度为0.8~1.0mm时两性期结束,开始雄花、雌花和完全花的差异发育,此后雄花和完全花的雄蕊原基快速增大,雌花和完全花的雌蕊原基开始分化为柱头和子房。在3种花芽发育过程中,完全花的花芽在两性期后明显比同时期的雄花、雌花的花芽长度更长。全雌系中的"畸形雌花"出现在两性期后,雌蕊原基的凹陷发育过程受阻,而本该停止发育的雄蕊原基继续分化,最终发育成可产生少量成熟花粉粒的雄蕊。     

几个油桃品种需冷量的研究

采用河北顺平露地栽培油桃早红珠、曙光与瑞光5号枝条为试材,比较了不同低温累积量下的萌芽率,并采用7.2℃低温模型和犹他模型对3个品种的需冷量进行估算。结果表明:瑞光5号的需冷量最高,花芽与叶芽分别为7607、00 h;曙光需冷量最低,花芽与叶芽均为640 h;早红珠介于二者之间,花芽与叶芽需冷量分别为7006、40 h;同一品种需冷量年际间差异不大;通过对7.2℃低温模型和犹他模型作比较,发现在该地区7.2℃低温模型更适合。     

树莓花芽分化的观察

1991～1992年,对树莓花芽分化时期的形态特征及发育进程进行了定期观察。结果表明,树莓花芽分化始期为8月末,9月中下旬进入高峰期,约60～70d。形态特征是雏梢生长点向上隆起成半球状。10月上旬至翌年4月中旬,随初生髓部的伸展,半球状生长点(顶花序原基)向前推进,随后形成腋花序原基,即为花序原基分化期。随同冬芽萌发展叶,依次进入花蕾、萼片、花瓣、雄、雌蕊原基的芽外分化阶段,各期约7～15d。至5月中旬出现花药和胚珠原始体。此期距结果新梢的花序显露还有2～3d。基生枝下部花芽分化始期比中上部迟一个月,分化数量也有较大下降。     

萝卜花芽分化过程中茎尖和叶片碳水化合物含量的变化

 以萝卜冬性品种‘一点红’和春性品种‘短叶13’为材料，研究花芽分化过程中茎尖和叶片以及萌动种子碳水化合物含量的变化。萌动种子在5℃下处理20 d，然后在温暖(>15℃)、长日照(16h)下生长，于不同花芽分化时期测定可溶性总糖、蔗糖和淀粉含量。结果表明：在花芽分化期间，无论是茎尖或是叶片，可溶性总糖、蔗糖和淀粉含量的变化趋势在两个品种之间较为接近。随着花芽分化的继续，可溶性总糖含量呈先上升后下降的趋势；蔗糖和淀粉含量则一直呈现上升趋势，在花芽分化完成后再下降。叶片中可溶性总糖、蔗糖和淀粉含量始终低于茎尖。冬性品种的蔗糖和淀粉含量在整个花芽分化期间始终较低，但在花芽分化初期的可溶性总糖含量则高于春性品种。     

Initiation and development of pistillate flowers in Actinidia chinensis

Initiation and development of pistillate flowers in Actinidia chinensis Planch, cultivar ‘Hayward’ (kiwifruit, Chinese gooseberry) was followed using light and scanning electron microscopy. Results indicate that dormant buds contain undifferentiated primordia in the leaf axils. These primordia remain undifferentiated until shortly before bud break, approximately two months before full bloom, when the primordia become trilobed as bracts and lateral flower primordia are initiated. The lateral flowers often abort in this cultivar. Acropetal development of the terminal flower proceeds rapidly. Five to seven sepals are initiated, followed by a whorl of five to seven petals. Stamen initiation is centripetal and the anthers develop to produce inviable pollen. The central portion of the floral apex is converted into a large compound pistil with numerous hollow styles, each terminated by an open stigma.     

桃花芽休眠解除SSH文库构建及相关基因表达分析

 为了深入研究桃花芽休眠的分子机制,利用抑制差减杂交技术（SSH）,以解除休眠期的花芽的RNA为实验方Tester,以休眠期花芽的RNA为驱动方Driver,构建休眠解除cDNA文库,测定分析了180 个上调表达的cDNA 片段,测序成功128个,除去冗余序列,得到28个单一序列。对序列进行BLAST比对及功能注释,发现这些序列分别属于新陈代谢、氧化还原、信号转导、抗性相关等类别基因。运用qRT-PCR 技术对HisH3、Dhn 和Metallothionein基因进行检测,结果表明它们在花芽休眠解除过程中均上调表达。