Fruit Regulates Bud Sprouting and Vegetative Growth in Field-Grown Loquat Trees (Eriobotrya japonica Lindl.): Nutritional and Hormonal Changes

The effects of fruit on bud sprouting and vegetative growth were compared on fruiting and defruited loquat trees from fruit set onward. Carbohydrate and nitrogen content in leaves and bark tissues and hormone concentrations were studied during the fruit development and vegetative growth periods. On defruited trees, a significant proportion of buds sprouted in winter, whereas buds from fruiting trees sprouted only in the spring when fruit reached its final size. Furthermore, when panicles were completely removed in autumn, the buds also sprouted. In addition, fruit directly affected vegetative growth by reducing shoot length. An effect of sink removal (flower or fruit) promoting bud sprouting, regardless of the season, was then demonstrated. Neither soluble sugar concentration nor nitrogen fraction concentration in leaves or bark tissues was related to bud sprouting, but a certain nutritional imbalance was observed during the most active period of fruit development. Moreover, fruit sink activity significantly modified hormone content by increasing indole-3-acetic acid (IAA) and reducing zeatin concentrations, resulting in a higher IAA/zeatin ratio parallel to the lower bud sprouting intensity. Therefore, these changes caused by fruit removal are all related to vegetative growth, but there is no evidence that they are responsible for bud burst.     

Changes of endogenous hormones in lateral buds of chrysanthemum during their outgrowth

The character of branching for two chrysanthemum (Chrysanthemum × morifolium) cvs. Jinghai and Jingyun was observed, and the changes of endogenous hormones in apical and lateral buds were investigated to determine the relationship between the pattern of hormone distribution, apical dominance, and lateral bud outgrowth. The growth rate of Jinghai lateral buds was higher than that of Jingyun. In vegetative growth stage, IAA level in apical buds of Jingyun was significantly higher than in Jinghai. After flower induction, IAA level in apical buds of two cultivars decreased remarkably, but the IAA level decreased in Jingyun faster than in Jinghai. These results showed that the higher was the IAA level in apical buds the stronger was inhibition of lateral bud outgrowth. An increase in IAA and iP/iPA and a decrease in ABA concentrations were closely associated with lateral bud growth alterations in chrysanthemum.     

东北草地异质生境芦苇种群根茎芽年龄结构及输出规律

为明确异质生境条件下芦苇种群根茎芽年龄结构及输出规律,揭示芦苇种群的营养繁殖特性,采用单位土体挖掘取样,分别计数各龄级根茎芽的调查与统计方法,对东北草甸草原草甸土和盐碱土两个生境单优群落芦苇种群根茎芽动态进行比较分析。结果表明,两个生境芦苇种群根茎芽库主要均由6个龄级组成;草甸土生境在6—10月均为增长型年龄结构;盐碱土生境6—7月份为衰退型年龄结构,8月份为稳定型年龄结构,9—10月份为增长型年龄结构。根茎芽数量1—4a普遍以草甸土生境高于盐碱土生境,5—6a普遍以盐碱土生境高于草甸土生境,各龄级根茎芽数量与月份之间均符合y=a+bx直线关系(P0.05)。随着龄级的增加,休眠芽比率呈逐渐下降趋势,而萌发芽比率则呈逐渐上升趋势,5个生育期的休眠芽比率和萌发芽比率与龄级之间均符合y=a+bx直线关系(P0.01)。各龄级根茎的休眠芽具有一个相对稳定的萌发输出过程,草甸土生境根茎休眠芽按每年11%的比率萌发输出,而盐碱土生境根茎休眠芽按每年7%的比率萌发输出。虽然芦苇种群根茎芽年龄结构及年龄谱在异质生境中存在显著差异,但却有着相同的季节变化规律,均以不断形成新根茎的芽来维持着种群的营养繁殖更新。     

Low temperature stress-induced biochemical changes affect stubble bud sprouting in sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> spp. hybrid)

A laboratory experiment was conducted to study the effect of low temperature stress on stubble bud sprouting and associated biochemical changes in sugarcane (Saccharum spp. hybrid). At 25°C, stubble bud sprouting was about 80%, whereas at 15 and 6°C, it was 56% and 23%, respectively. In stubble buds, the levels of reducing sugars and acid invertase were low, while IAA, total phenols and proline contents were high at low temperatures, as compared to normal temperature (25°C). Similarly, the specific activities of antioxidant enzymes, viz., catalase and peroxidase in stubble buds were higher at low temperatures than at normal temperature. The results indicate that poor sprouting of stubble buds at low temperatures appears to be due to a reduced availability of reducing sugars concomitant with a lower activity of acid invertase. An increased level of IAA together with toxicity build-up in situ due to an accumulation of total phenols may be responsible for the maintenance of dormancy in stubble buds at low temperatures. On the other hand, higher activities of catalase and peroxidase enzymes may protect stubble buds from an oxidative damage, while proline accumulates to act as an osmoprotectant under low temperature stress.     

Spatial and temporal changes in multiple hormone groups during lateral bud release shortly following apex decapitation of chickpea (Cicer arietinum) seedlings

Although the co-ordination of promotive root-sourced cytokinin (CK) and inhibitory shoot apex-sourced auxin (IAA) is central to all current models on lateral bud dormancy release, control by those hormones alone has appeared inadequate in many studies. Thus it was hypothesized that the IAA : CK model is the central control but that it must be considered within the relevant timeframe leading to lateral bud release and against a backdrop of interactions with other hormone groups. Therefore, IAA and a wide survey of cytokinins (CKs), were examined along with abscisic acid (ABA) and polyamines (PAs) in released buds, tissue surrounding buds and xylem sap at 1 and 4 h after apex removal, when lateral buds of chickpea are known to break dormancy. Three potential lateral bud growth inhibitors, IAA, ABA and cis -zeatin 9-riboside (ZR), declined sharply in the released buds and xylem following decapitation. This is in contrast to potential dormancy breaking CKs like trans -ZR and trans -zeantin 9-riboside 5'phosphate (ZRMP), which represented the strongest correlative changes by increasing 3.5-fold in xylem sap and 22-fold in buds. PAs had not changed significantly in buds or other tissues after 4 h, so they were not directly involved in the breaking of bud dormancy. Results from the xylem and surrounding tissues indicated that bud CK increases resulted from a combination synthesis in the bud and selective loading of CK nucleotides into the xylem from the root.     

藤本月季“安吉拉”花芽分化形态结构及内源激素变化研究

以藤本月季“安吉拉”为试验材料,通过石蜡切片、体视显微镜观察及内源激素的测定,研究花芽分化过程的形态结构及内源激素的变化,为花期调控、景观品质的提升及相关育种工作提供基础数据。藤本月季“安吉拉”花芽各部分分化顺序由外向内进行,分为5个时期,共历时30 d,首先是生长锥呈圆锥状突起的形态分化期;扁平生长锥周围出现5个突起,即为萼片原基分化期;萼片原基的内方分化出成轮状的多个花瓣原基,即为花瓣原基分化期;花瓣原基基部从上向下分化出多轮雄蕊原基,即为雄蕊原基分化期;扁平的生长锥顶端突起形成多个雌蕊原基,为雌蕊原基分化期。随花芽分化进程脱落酸(ABA)、细胞分裂素(CTK)浓度变化规律相似,均呈先升高再下降趋势,萼片原基分化期其浓度均显著高于其他时期;生长素(IAA)浓度呈逐渐上升的趋势;赤霉素(GA)浓度呈逐渐下降趋势。随花芽分化进程IAA/GA和IAA/ABA比值呈逐渐上升趋势,CTK/GA和(ABA+CTK)/GA比值在萼片原基分化期显著高于形态分化期。内源激素测定结果表明:ABA、CTK浓度在萼片原基分化期显著升高与花芽分化诱导有关,较低的IAA浓度以及GA浓度的降低有利于藤本月季“安吉拉”的花芽分化;萼片原基分化期CTK/GA和(ABA+CTK)/GA比值升高可能与花芽分化诱导有关,高水平的IAA/ABA和IAA/GA比值可能与花器官原基的进一步发育相关。     

Periodicity of bud bursting in willow (Salix viminalis) as affected by growth regulators

Saunders, P. F. and Barros, R. S. 1987. Periodicity of bud bursting in willow ( Salix viminalis ) as affected by growth regulators.
Lateral vegetative buds of willow ( Salix viminalis L.) were only innately dormant for 3–5 weeks in October; during this time their apices were correlatively inhibited by the bud leaflets. Exogenous gibberellins stimulated the opening of cultured buds when the plants were dormant or entering dormancy. As dormancy was being released, however, cultured buds became more responsive to exogenous cytokinins. Thus the demand for gibberellins and cytokinins for bud opening seemed to be sequential rather than simultaneous. Dormant buds cultured in the presence of abscisic acid remained unopened, but they opened after a chilling treatment. Subsequent growth of such buds as measured by dry matter accumulation, was observed only if a cytokinin was added to the medium.     

Gibberellins and bud break,vegetative shoot growth and flowering in Metrosideros collina cv. Tahiti

Applications of the growth promotive gibberellins (GAs) GA₄ and 2,2-dimethyl GA₄, and of C-16,17 endo-dihydro GA₅, which is known to promote flowering while inhibiting stem growth in the long-day grass Lolium temulentum, were made to micropropagated plants of Metrosideros collina cv. Tahiti, a highly ornamental cultivar with an intermittent flowering pattern. Gibberellin A₄ and 2,2-dimethyl GA₄ stimulated vegetative growth both in elongating shoots, and internodes of shoots developing from buds that were quiescent at the time of GA application. Abscission of the apices of expanding shoots, a feature of mature Metrosideros plants, was inhibited by these GAs, the rejuvenation of micropropagated plantlets being enhanced. However, C-16,17 endo-dihydro GA₅ differed from GA₄ and 2,2-dimethyl GA₄ by having no promotive effects on vegetative growth, and no inhibition of apical abscission. Notwithstanding this contrasting effect on vegetative growth, high doses of GA₄ or C-16,17 endo-dihydro GA₅ similarly reduced flowering on shoots to which either GA was applied. Reduced flowering in response to applied GAs is common in many woody angiosperms, and in this instance was probably the combined result of abortion of developing floral structures in quiescent buds, and a preferential inhibition of bud break for floral buds relative to vegetative buds, particularly by GA₄. Finally, both C-16,17 endo-dihydro GA₅ and GA₄ strongly inhibited bud break in this woody angiosperm, although GA₄ could initially stimulate bud break when applied to vegetative buds close to the expansion stage. The above findings, in toto, highlight the sensitivity of Metrosideros to both classes of GA in a variety of growth and development processes.     

Low temperature influence on flowering in Citrus. The separation of inductive and bud dormancy releasing effects

The flowering response of Owari Satsuma mandarin ( Citrus unshiu Marc) to low temperature treatments has been determined using potted trees and in vitro bud cultures. In potted trees the chilling treatments released bud dormancy and enhanced both sprouting and flowering, but these two responses could not be separated. However, bud cultures showed no dormancy, and a specific effect of low temperature on flower induction was demonstrated. Low temperature appears to have a dual effect, releasing bud dormancy and inducing flowering. Potential flower buds have a deeper dormancy than vegetative buds, and the first stages of flower initiation seem to occur before the winter rest period.     

Growth Substances and Dormancy in Ceratophyllum demersum

Ceratophyllum demersum L. occurs in winter in the dormant form, in summer in the vegetative form. Factors that affect growth and dormancy in Ceratophyllum were studied. After several weeks of severe winter conditions the plants changed from dormant to quiescent state. Under natural conditions Ceratophyllum plants remain quiescent for several months, due to unfavourable growth conditions. Experimentally the dormant could also be broken by high and low temperature treatments (shocks), and most effectively by addition of GA, An attempt to induce dormancy in full grown plants by the addition of ABA under extreme summer or winter conditions proved unsuccessful. The IAA and ABA contents in the plants were measured during the year. In winter the concentration of ABA was high and that of IAA low, whereas in summer the IAA concentration increased and that of ABA was variable. IAA only slightly antagonized the inhibition of growth by ABA. Both the growth regulators were readily taken up from the culture medium, as was confirmed by a study with the radioactive labelled compounds. The uptake rate of IAA was significantly higher than that of ABA. being 762 μg and 3.26, μg per plant in 24 h, respectively. GA, was found to have a strong antagonistic effect on the ABA induced growth inhibition. The total GA activity in dormant and quiescent plants was similar, in full grown plants it was much lower. In the dormant state a large part of GA was in a bound form, whereas during quiescence relatively more GA occurred in a free state in the plants.     

The Control of Apical Bud Growth and Senescence by Auxin and Gibberellin in Genetic Lines of Peas

Pea (Pisum sativum L.) lines G2 (dwarf) and NGB1769 (tall) (Sn Hr) produce flowers and fruit under long (LD) or short (SD) days, but senesce only under LD. Endogenous gibberellin (GA) levels were inversely correlated with photoperiod (over 9-18 h) and senescence: GA20 was 3-fold and GA1 was 10- to 11-fold higher in flowering SD G2 shoots, and the vegetative tissues within the SD apical bud contained 4-fold higher levels of GA20, as compared with the LD tissues. Prefloral G2 plants under both photoperiods had GA1 and GA20 levels similar to the flowering plants under LD. Levels of indole-3-acetic acid (IAA) were similar in G2 shoots in LD or SD; SD apical bud vegetative tissues had a slightly higher IAA content. Young floral buds from LD plants had twice as much IAA as under SD. In NGB1769 shoots GA1 decreased after flower initiation only under LD, which correlated with the decreased growth potential. We suggest that the higher GA1 content of G2 and NGB1769 plants under SD conditions is responsible for the extended vegetative growth and continued meristematic activity in the shoot apex. This and the increased IAA level of LD floral buds may play a role in the regulation of nutrient partitioning, since more photosynthate partitions of reproductive tissue under LD conditions, and the rate of reproductive development in LD peas is faster than under SD.     

棉花花芽分化时期茎尖内源激素的变化

实验结果表明,从子叶展平后到肉眼可花芽（现蕾）,所测几种激素（ABA、IAA、GA3、iPA、ZR）的含量均表现出明显的动态变化,而且在花芽分化临界期表现出最显著的变化（出现高峰或出现低峰）。推测所测几种激素均与花芽分化有密切关系。其中ABA、GA3和CTK（iPA、ZR）在花芽分化临界期时,其含量变化均呈现出一个高峰;而IAA则在花芽分化临界期时出现一个低峰。经比较分析得知,随着花芽分化的进行,ABA/IAA、GA3／IAA、CTK／IAA均表现一个较明显的变化规律。即从子叶展平时起,其比值开始上升,到花芽开始分化时达到一个峰值,之后逐渐下降,并维持在一个较稳定的水平。显然,ABA／IAA、GA3／IAA、CTK／IAA在棉花的花芽分化过程中起着重要的调控作用。由此推测,增加植物体内的ABA、GA3、CTK的含量或降低IAA的含量,都可以促进棉花的花芽分化;反之则抑制棉花的花芽分化。     

Effect of plant growth substances on the growth of axillary buds in cultured stem segments of Phaseolus vulgaris L.

The hormonal control of axillary bud growth was investigated in cultured stem segments of Phaseolus vulgaris L. When the stem explants were excised and implanted with their apical end in a solid nutrient medium, outgrowth of the axillary buds-located at the midline of the segment-was induced. However, if indoleacetic acid (IAA) or naphthaleneacetic acid (NAA) was included in the medium, bud growth was inhibited. The exposure of the apical end to IAA also caused bud abscission and prevented the appearance of new lateral buds.In contrast to apically inserted segments, those implanted in the control medium with their basal end showed much less bud growth. In these segments, the auxin added to the medium either had no effect or caused a slight stimulation of bud growth.The IAA transport inhibitor N-1-naphthylphthalamic acid (NPA) relieved bud growth inhibition by IAA. This suggests that the effect of IAA applied at the apical end requires the transport of IAA itself rather than a second factor. With the apical end of the segment inserted into the IAA-containing medium, simultaneous basal application of IAA relieved to some extent the inhibitory effect of the apical IAA treatment. These results, together with data presented in a related article [Lim R and Tamas I (1989) Plant Growth Regul 8: 151–164], show that the polarity of IAA transport is a critical factor in the control of axillary bud growth.Of the IAA conjugates tested for their effect on axillary bud growth, indoleacetyl alanine, indoleacetic acid ethyl ester, indoleacetyl-myo-inositol and indoleacetyl glucopyranose were strongly inhibitory when they were applied to the apical end of the stem explants. There was a modest reduction of growth by indoleacetyl glycine and indoleacetyl phenylalanine. Indoleacetyl aspartic acid and indoleglyoxylic acid had no effect.In addition to IAA and its conjugates, a number of other plant growth substances also affected axillary bud growth when applied to the apical end of stem segments. Myo-inositol caused some increase in the rate of growth, but it slightly enhanced the inhibitory effect of IAA when the two substances were added together. Gibberellic acid (GA₃) caused some stimulation of bud growth when the explants were from younger, rather than older plants. The presence of abscisic acid (ABA) in the medium had no effect on axillary bud growth. Both kinetin and zeatin caused some inhibition of axillary buds from younger plants but had the opposite effect on buds from older ones. Kinetin also enhanced the inhibitory effect of IAA when the two were applied together.In conclusion, axillary buds of cultured stem segments showed great sensitivity to auxins and certain other substances. Their growth responded to polarity effects and the interaction among different substances. Therefore, the use of cultured stem segments seems to offer a convenient, sensitive and versatile test system for the study of axillary bud growth regulation.     

剥鳞和激素处理对大樱桃花芽休眠解除及内源激素变化的影响

采用高效液相色谱法(HPLC)分析了剥鳞与激素处理对大樱桃花芽休眠解除及内源生长素(IAA)、赤霉素(GAD、玉米素(ZT)和脱落酸(ABA)变化的影响。结果表明,花芽中的ABA主要分布于鳞片内,鳞片中的GA3和ZT含量远低于去鳞芽,也低于完整芽。剥鳞能明显增加休眠花芽中内源GA2和ZT的含量,降低ABA的含量,对IAA含量的影响不大。剥鳞降低了ABA／GA3、ABA／ZT的比值,使花芽向促进生长、抑制休眠的方向转化。同时,休眠前、后期剥鳞均能明显提高萌芽率,中期剥鳞效果不明显。剥鳞后施用外源激素随休眠时期不同而有不同的破眠效果,早期剥鳞GA3的效果最好,6-BA次之,IAA最差;中期破眠效果不如早期,GA。和6-BA没有明显差别;后期以6-BA效果最好,其次是GA3和IAA;3次处理中ABA均明显抑制花芽萌发。     

Polyamine levels in buds and twigs of Tilia cordata from dormancy onset to bud break

The fluctuations of free and bound polyamines (PAs) were studied in vegetative buds and underlying twigs of linden (Tilia cordata L.) from August to May, to assess the connection between PA levels and seasonal cycles of growth and dormancy. Outer and inner bud scales and shoot tips (short shoot tips with leaf initials in contiguous short internodes) were analyzed separately, as were phloem with cortex and xylem with pith tissue from twigs. Seasonal variations in PA levels were present in buds and twigs during the research period. The most abundant PA in buds and twigs in free and bound forms was spermidine followed by putrescine. PA amounts were low in buds and twigs in autumn. In twig tissues, free PAs were predominant whereas in bud scales, bound PAs accumulated over free PAs in autumn, first in inner scales and later in outer scales as well. PA levels did not increase dramatically during the onset of dormancy in autumn but lower temperatures and probable cold hardening correlated positively with bound PAs in bud scales. In shoot tips with leaf initials, and contiguous short internodes, free putrescine and spermidine levels rose simultaneously with bud burst and new growth, while bound PAs diminished quite radically from temporary bud scales and from growing shoot tips.     

Epicormic Bud Development in Quercus robur L. Studies of Endogenous IAA, ABA, IAA Polar Transport and Water Potential in Cambial Tissues10

Seasonal measurements of IAA,³ made using GC-MS, ⁴ indicatedthat in Q. robur the spring initiation of cambial activity andonset of visible bud outgrowth in the canopy is preceded byan increase in cambial region IAA. The effects of notch-girdlescut into the bole indicated that IAA in the cambial region laterwas present in separate physiological pools, with only the polar-transportedfraction affecting epicormic bud outgrowth. The stage in thespring when the epicormic buds grew out coincided with an increaseboth in cambial region IAA and in the capacity of cambial explantsfor IAA polar transport. Thus the stimulus needed by the epicormicbuds to overcome inhibition by polar-transported IAA appearedto be self-generated. The observed effects of exogenous hormoneson epicormic bud outgrowth from stem explants indicated thatthis stimulus might be cytokinin. The seasonal changes detectedin cambial region ABA³ were consistent with a role for stress-inducedABA in the induction of epicormic bud dormancy after canopydevelopment during the summer. No consistent effects of standthinning on cambial region IAA, ABA, water potentials or watercontents were detected, although polar transport of exogenousIAA by cambial region explants removed in the spring was reducedby thinning. Key words: Epicormic buds, cambium, hormones