Endogenous Gibberellins in the Xylem Exudate from Apple Trees

In the xylem exudate extracted from the current-year stems of apple (Malus domestica Borkh.), gibberellins A₁₅, A₁₇, A₁₈, A₁₉, A₂₃, A₄₄, and A₅₃ were identified, and 16,17-dihydro-17-hydroxy GA₁₉ was presumed from full-scan mass spectra and Kovats retention indices.     

Distribution of Endogenous Gibberellins in Vegetative Shoots of Rice

Levels of endogenous gibberellins in rice seedlings (Oryza sativaL., cv. Nipponbare) were compared between young and old leavesat the 4- and 5-leaf stages. The levels of GA₁, GA₁₉ and GA₅₃were higher in the youngest leaf than in older leaves at the5-leaf stage, but they did not differ significantly betweenthe leaf sheath and the leaf blade. At the 4-leaf stage, thelevel of GA₁, was highest in the third leaf sheaths which containedyoung elongating tissues. These results indicate that gibberellinsare synthesized in young vegetative tissues to promote theirelongation growth. The levels of GA₁ in the youngest leaf sheathsof two cultivars of dwarf rice, Tan-ginbozu and Waito-C, wereapproximately 10% of that in the normal rice at the 5-leaf stage.This result could explain the retardation of shoot elongationin these dwarf cultivars. (Received February 15, 1995; Accepted June 1, 1995)     

Apple Proliferation Epidemics Detected in Scab-Resistant Apple Trees

In the Friuli-Venezia Giulia, a region of Italy, where serious epidemics of apple proliferation (AP) are known to occur, varieties resistant to scab (Venturia inaequalis (Cke.) Wint.) are increasingly being used in new orchards. The most important cvs are Florina. Prima and Priscilla. These varieties were cultivated according to organic farming regimes with no insecticides used. The results obtained in two orchards during a 7-year period of investigation indicated that the three varieties resistant to scab are highly susceptible to AP. Florina was most susceptible (high infection rate) to AP while Priscilla was most sensitive (severely affected). The identification of the disease was based on symptom expression, DAPI (4–6-diamidino-2-phenylindole) fluorescence technique, electron microscopy observations and by polymerase chain reaction (PCR). Neither complete spontaneous recovery nor death of AP-infected plants was noticed. The pattern of natural diffusion of AP does not seem to be uniform, the affected trees may be in line or grouped in certain spots of the orchards. This may indicate the activity of a not very mobile vector. It can be concluded that planting of Florina, Prima and Priscilla should be discouraged in areas where AP is a problem, particularly when organic farming regimes are being applied.     

14C-Studies on Apple Trees. II. Distribution of Photosynthates from Top and Base Leaves from Extension Shoots

The photosynthates from leaves from extension shoots may be used either for new growth of the shoot itself, or for growth in other parts of the tree. An attempt has been made to elucidate this problem by determining the content of ¹⁴C in long shoots to which ¹⁴CO₂ was applied either through fully developed leaves at the base, or through very young leaves at the apex. In the case of ¹⁴C application at the base, 80 per cent or more of the ¹⁴C initially taken up disappears from the shoot, and only a very minor part is translocated upwards in the shoot. When the leaves at the apex are exposed, on the other hand, 80 per cent of the ¹⁴C absorbed is retained in the leaves and shoot components treated as long as there is still considerable terminal growth taking place, although a small percentage is deposited in the lower parts of the shoot. At the same time, a much higher proportion is incorporated into methanol-insoluble components. As terminal growth decreases, a larger proportion of the ¹⁴C activity of the apex leaves also disappears from the shoot. The distribution of activity between the sorbitol, sucrose, glucose and fructose fractions was not significantly different in young and in fully developed leaves. The ¹⁴C labelling in the sugar fraction was highest for sorbitol, then sucrose, but decreases with time compared to glucose and fructose.     

Endogenous Gibberellins in Elongating Shoots of Clones of Salix dasyclados and Salix viminalis

Elongating shoots of rapidly growing clones of Salix viminalis L. (clone 683-4) and Salix dasyclados Wimm. (clone 908) harvested in early August were analyzed for endogenous gibberellins (GA). Distribution of GA-like activity, determined by Tan-ginbozu dwarf rice microdrop bioassay after reverse phase C₁₈ high performance chromatography, was similar for both species. For S. dasyclados, combined gas chromatography-selected ion monotoring (GC-SIM) yielded identifications of GA₁, GA₈, GA₁₉, GA₂₀, and GA₂₉. Identifications of GA₄ and GA₉ were also made using co-injections of known amounts of [17, 17-²H₂]GAs. By bioassay, the main activity was GA₁₉-like in both species. Gibberellin A₁, GA₁₉, and GA₂₀ concentrations were approximated by GC-SIM using co-injections of known amounts of [17,17-²H₂]GAs. Both bioassay and GC-SIM results indicated very high concentrations of GA₁₉ and GA₂₀ (about 6000 nanograms per kilogram fresh weight shoot tissue using GC-SIM: 800 ng using bioassay), compared to the concentration of GA₁ (about 130 nanograms per kilogram fresh weight using either GC-SIM or bioassay).     

2个芽变苹果品种枝条主要性状比较

短枝型芽变品种是中国苹果矮化密植栽培可以利用的重要种质资源,研究其形成的生理基础和相关基因,为进一步探索苹果短枝型芽变形成机理奠定基础。以枝条快速生长期的普通型品种‘烟富8号’和短枝型品种‘惠民短枝’叶片、茎与茎尖作为试验材料,测定枝条粗度和节间长度,采用HPLC法测定内源激素(IAA、GA3和ABA)和可溶性糖(葡萄糖、蔗糖、果糖、山梨糖醇)含量,应用实时定量qRT-PCR技术比较分析激素相关基因在不同品种中的表达特性,为研究苹果枝条发育调控机理提供支撑。结果表明,‘烟富8号’的节间长度高出‘惠民短枝’1.2倍,而枝条粗度显著低于‘惠民短枝’;茎中的蔗糖和山梨糖醇含量分别显著高于‘惠民短枝’2.5倍和1.3倍,茎尖中的葡萄糖含量仅为‘惠民短枝’的0.3倍;茎和茎尖中的GA 3和IAA含量、TIR1和GA20ox基因的表达水平显著高于‘惠民短枝’,而ABA含量、SnRK2和PYL基因表达水平显著低于‘惠民短枝’;叶片中GA20ox基因的表达水平显著高于‘惠民短枝’。研究推测,较低浓度的GA3、IAA、蔗糖和山梨糖醇,及较高浓度的ABA和葡萄糖与短枝型苹果品种的形成密切相关。     

Gibberellins in Light-Grown Shoots of Pisum sativum L. and the Influence of Reproductive Development

The presence of GA₉, GA₁₉ and GA₂₀ was demonstrated by gas chromatography/massspectrometry (GC/MS) and the presence of GA₄₄ strongly indicatedby GC/MS in selected ion monitoring mode (GC/SIM) in extractsof shoots of light-grown tall peas (Pisum sativum L.). Usingthe rice seedling bioassay with cv. Tan-ginbozu, the levelsof gibberellins in pea shoots were monitored from early shootgrowth through to apical senescence in a tall pea line. Levelsof activity corresponding to GA₂₀, GA₁₉ and GA₄₄ remained relativelystable in the shoot despite reproductive development and apicalsenescence. The level of GA₁-like activity increased to a maximumwhen the leaves had between 7 and 9 leaves expanded and decreasedonly with apical senescence. The na gene which blocks the productionof biologically active gibberellins in shoots but not in developingseed, was also operative in pod walls, with na pods containinglittle or no significant gibberellin-like activity when comparedto na pods at contact. This occurred despite the presence ofrelatively high levels of gibberellins in developing seed atthe same time. The results suggest that there is little or nosignificant leakage of biologically active gibberellins fromdeveloping seed to pods or shoots. Extracts of pods of tallpeas with Na contained low levels of gibberellin-like activitybut like developing seed, contained little or no significantGA₁-like activity despite the presence of significant GA₁-likeactivity in shoot extracts of tall peas. (Received March 11, 1986; Accepted May 27, 1986)     

Gradients in the Nitrogenous Constituents of the Sap extracted from Apple Shoots of Different Ages

A comparison was made of the nitrogenous constituents in thesap extracted under vacuum from apple shoots of different ages,as regards changes both with season and in response to fertilizernitrate applied in summer or autumn. Before blossoming the N concentration of the sap changed markedlywith age of shoot, with the values doubling in the samples fromthe proximal half of the 3-year-old wood to the distal 2-year-oldsection, followed by a significant decrease in the 1-year-oldshoot. After blossoming the gradients in sap concentration wereless pronounced but usually the lowest values were found inthe youngest part of the shoot. Fourteen days after a soil application of nitrate in July therewas a marked increase in the concentration of asparagine inthe sap, but only in the 3-year-old section of the shoot. Sevendays later the xylem sap from all parts of the shoot containedincreased levels of asparagine, aspartic acid, and glutamine. No changes in the xylem sap of shoots in response to fertilizerapplied in October were observed until the following April.Then increased amounts of asparagine and glutamine were foundin all sections, with the greatest increase being seen in theyoungest part. It is suggested that this was due to acceleratedmobilization of N reserves into the xylem sap in response togrowth regulators originating in the roots rather than to movementof recently absorbed nutrients.     

Bacterial Blister Bark of Apple Trees in Italy

At the beginning of spring 1996, raised, brown areas along the bark of trunk and twigs were observed on young apple trees in Piedmont (northern Italy). In many cases the epidermis flaked off. Longitudinal cracks accompanied by necrosis of the tissues beneath the bark were also observed. In one orchard the disease caused the death of 2500 trees. Biochemical, nutritional and pathogenicity tests, as well as the comparison of whole-cell protein profiles of the isolates with type-strains, indicated that Pseudomonas syringae pv. syringae was the causal agent of the disease. Bacterial blister bark remains a threat for apple cultivation also in Italy, especially in orchards planted in sandy soils.     

The Pruning Response of One-year Apple Trees

The response to pruning, in the simple woody system exemplifiedby 1-year-old rooted apple shoots, could be summarized by theequation irrespective of the amount of growth or of whether all new shootsor only two were allowed to develop. In a group of smaller plants,the proportion of new stem increased slightly. The responsecould be largely attributed to a close relation between thetotal increment and the thickening of the old stem which wasfound to be Increase in weight of the plants was favoured by treatmentspromoting early bud-break and rapid development of leaf area.It was not simply related to pruning.     

Endogenous Gibberellins in the Vegetative Shoots of Tall and Dwarf Cultivars of Phaseolus vulgaris L.

A series of 13-hydroxygibberellins, gibberellin A₁ (GA₁), GA₁₉,GA₂₀, GA₄₄ and GA₅₃, were identified by GC/MS (full scan) fromvegetative shoots of tall (cv. Kentucky Wonder) and dwarf (cv.Masterpiece) Phaseolus vulgaris L. It is suggested that GA₁is active per se in the control of shoot elongation of P. vulgarisL., and that dwarfism in Masterpiece is not due to shortageof the active GA, but to its low ability to respond to the bioactiveGA. (Received August 29, 1988; Accepted November 21, 1988)     

Redistribution of Endogenous Indoleacetic Acid, Abscisic Acid and Gibberellins in Geotropically Stimulated Ribes nigrum Shoots

The presence of IAA, ABA and gibberellins in extracts of shoots of Ribes nigrum was demonstrated by gas-liquid chroma-tography (GLC) for both IAA and ABA and by the lettuce hypocotyl assay for gibberellins. Quantitative estimation of the three substances in extracts from upper and lower halves of shoots which had been kept horizontal, and which showed negative geotropic response after 4 h, indicated a redistribution of hormones during the geotropic stimulation. The ratio of the hormones in lower and upper halves was 3.8:1 and 2.8:1 for IAA and giberellins respectively, whereas the ratio of ABA in upper and lower halves was 2.1:1. There is, however, no evidence for the participation of gibberellins and ABA in the early development of negative geotropic curvatures, since shoots of intact Vicia faba seedlings treated with 100 mg/1 solution of GA₃, ABA and 10 mg/1 IAA for 30 min prior to geotropic stimulation, developed negative geotropic curvatures, although shoots pretreated with 50 and 100 mg/1 IAA did not develop curvature.     

Ethylene Evolution Stimulated by Succimc Acid-2,2-Dimethylhydrazide in Apple Shoots

The rate of ethylene production in the shoot tips of the apple cultivar ‘Ingrid Marie’ (Red motant) after succinic acid-2,2-dimethylhydrazide (SADH) treatment was investigated. The shoots were treated with SADH at 12.5, 25 or 50 mM in the months of June, July and August. The samples were analysed 7,15, 30 and 60 days after SADH spray. Ethylene production was considerably higher in the SADH-treated shoots than in the untreated ones. Application of 12.5 or 25mMSADH late in June stimulated ethylene production 3-fold, while 50 mM produced a 5-fold increase in ethylene production 7 days after spraying. There was a continuous decrease in ethylene production at the subsequent samplings. In untreated control shoots there was a slight increase. However, even 60 days after spraying the shoots treated with 50 mM had higher ethylene production than the control shoots. The same relationship was found in the shoots treated in the months of July and August. A parallelism has been established between the rate of ethylene production and growth retardation, A residual effect of SADH treatment in earlier years was demonstrated and is discussed.     

Gibberellins from mangrove plants

Gibberellins were isolated from three mangrove plants: A₁ and A₃ from Sonneratia apetala; A₃, A₅ and A₉ from Rhizophora mucranata and A₃, A₄ and A₇ from Bruguiera gymnorhiza. Biological activity of these gibberellins were examined using three bioassays.