Hormone Profiling by LC-QToF-MS/MS in Dormant <Emphasis Type="Italic">Macadamia integrifolia</Emphasis>: Correlations with Abnormal Vertical Growth

A method for analyzing multiple plant hormone groups in small samples with a complex matrix was developed to initiate a study of the physiology of abnormal vertical growth (AVG) in Macadamia integrifolia (cv. HAES344). Cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), and auxins were detected in xylem sap and apical and lateral buds using high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QToF-MS/MS). The extraction method separated compounds with high sensitivity in positive (CKs) and negative (ABA, auxins, GAs) modes of QToF-MS/MS. CK profiles differed in xylem sap and apical and lateral buds irrespective of AVG symptoms. Trans-zeatin riboside (t-ZR) was dominant in sap of normal and AVG trees (∼4 and 6 pmol g⁻¹ FW, respectively). In apical buds isopentenyl adenine (iP) (∼30 pmol g⁻¹ FW) was the most abundant CK, and in lateral buds trans-zeatin (t-Z) (22–24 pmol g⁻¹ FW) and iP (24–30 pmol g⁻¹ FW) were the most abundant. t-Z levels of AVG trees were higher in apical buds (13.88 vs. 6.6 pmol g⁻¹ FW, p < 0.05) and lower in sap (0.16 vs. 0.51 pmol ml⁻¹, p < 0.005) compared to normal trees. ABA in lateral buds was 1.9 times higher (p < 0.001) in AVG. IAA was below quantification, whereas indole-3-butyric acid (IBA) was consistently present. GA₇ was the dominant GA in apical and lateral buds of all trees (100–150 pmol g⁻¹ FW). GA_{3, 4, & 9} were consistently present at low concentrations (<12 pmol g⁻¹ FW) in buds. GAs_{1, 3, & 9} were detected in xylem sap at low concentrations (<0.5 pmol g⁻¹ FW). Differences in sap amino acids (AA) were also assessed. In sap from AVG trees, asparagine and glutamine increased significantly (p < 0.05) in their contribution to total AA. Potential AVG hormone correlations are discussed.     

Gibberellins do not act against abscisic acid in the regulation of bulb dormancy of Allium wakegi Araki

Abscisic acid (ABA) is involved in bulb dormancy of Alliumwakegi Araki. We examined the antagonistic role of gibberellins(GAs)against ABA in the regulation of this dormancy. The concentrations of ABA andGAs in the basal leaf sheaths or bulbs of A. wakegi cv.Kiharawase were investigated during growth in the field and postharveststorage.The concentration of ABA in the basal leaf sheaths began to increase about onemonth before they began to swell, reached a maximum shortly after bulbharvesting, and decreased during postharvest storage. The plants showed bulbdormancy accompanied with the change in ABA concentration. GA1,GA3, GA4, GA12, GA15, GA19, and GA20 were identified in the basal leaf sheaths of A. wakegi from Kovats retention indices (KRI) andfull-scan mass spectra by gas chromatography - mass spectrometry (GC-MS)analysis. The concentrations of all classes of GAs in the basal leaf sheathsestimated by the dwarf rice micro-drop assay increased transitorily shortlybefore they began to swell, and decreased rapidly during bulb development. Bulbdormancy had already been induced when the concentration of the GAs becamemaximum. All the GAs in the bulbs remained at a low level during postharveststorage, when bulbs were gradually released from dormancy. The concentrationsof GA1+3, GA4, GA15, and GA20 inthe bulbs increased after sprouting of the bulbs planted in moist vermiculite.Hence, the state of bulb dormancy is considered to be independent of the GAconcentrations of in the basal leaf sheaths or bulbs of A.wakegi.     

激素信号在调节果树花芽发端假说的概述

概述了Lavee和Bangerth两个激素信号调节花芽发端假说的内容和证据,并分析了这两个假说的优缺点。认为旺盛营养生长的梢尖或正在发育果实的种子产生的极性运输的生长素（IAA）可能是抑制果树花芽发端的信号。尚不能确定来自正在发育果实种子的赤霉素（GA）自身是抑制花芽发端的信号,还是参与调节花芽发端信号的产生。营养芽中高水平的细胞分裂素（CTK）促进花芽发端,可能与较弱的IAA信号有关。同时指出,激素信号调节花芽发端的机理还有待完善。     

Flower development in the passion fruit Passiflora edulis requires a photoperiod‐induced systemic graft‐transmissible signal

Different organisms use gradual seasonal changes in photoperiod to correctly time diverse developmental processes, such as transition to flowering in plants. Florigen is a systemic signal formed in leaves exposed to specific environmental cues, mainly photoperiodic, and capable of triggering flower induction in several species. Here we show that in Passiflora edulis, a perennial climbing vine, flower initiation occurs throughout the year; however, without long photoperiods, flower primordia show arrested growth and differentiation at an early stage. Our results support the existence of a positive, systemic, graft‐transmissible signal, produced in mature leaves under LDs, that is required for normal flower development beyond sepal formation. Our results also suggest that Gibberellin acts to inhibit flower development. We provide evidence for genetic variation in the response to short photoperiods. A genotype capable of forming developed flowers under short photoperiods produces a positive graft transmissible signal allowing normal flower development under short days in a cultivar which normally aborts flower development under these conditions. We believe these findings contribute towards discovering the chemical nature of this interesting mobile signal involved in flower development.     

Biological activities of fluorogibberellins and interactions with unsubstituted gibberellins

The activities of two mono- and two di-fluorogibberellins are compared with the equivalent unfluorinated compounds in the barley half-seed, lettuce hypocotyl and Tanginbozu dwarf rice bioassays. Interactions between the substituted and unsubstituted gibberellins are also examined. It is concluded that the effects of fluorination are dependent upon the site and degree of substitution and vary with the type of bioassay tissue involved. In the interaction studies the fluorogibberellins generally proved inhibitory, and competitive inhibition was indicated.     

Conjugates of abscisic acid, brassinosteroids, ethylene, gibberellins, and jasmonates

Phytohormones, including auxins, abscisic acid, brassinosteroids, cytokinins, ethylene, gibberellins, and jasmonates, are involved in all aspects of plant growth, and developmental processes as well as environmental responses. However, our understanding of hormonal homeostasis is far from complete. Phytohormone conjugation is considered as a part of the mechanism to control cellular levels of these compounds. Active phytohormones are changed into multiple forms by acylation, esterification or glycosylation, for example. It seems that conjugated compounds could serve as pool of inactive phytohormones that can be converted to active forms by de-conjugation reactions. Some conjugates are thought to be temporary storage forms, from which free active hormones can be released after hydrolysis. It is also believed that conjugation serves functions, such as irreversible inactivation, transport, compartmentalization, and protection against degradation. The nature of abscisic acid, brassinosteroid, ethylene, gibberellin, and jasmonate conjugates is discussed.     

The effect of fruit-removal on cytokinins and gibberellin-like substances in grape leaves

Removal of fruit from potted cuttings of Vitis vinifera L. increased the concentration of a cytokininglucoside in leaf tissue extracts and decreased the level of extractable gibberellin-like substances. The glucoside (of zeatin riboside) is not present in xylem exudate of V. vinifera L., and appears to be synthesized in the leaves. Berry extracts contain zeatin-riboside and smaller amounts of cytokinin-glucoside. The changes in the level of these hormones are discussed in relation to previous results on abscisic acid and phaseic acid levels in grape leaves.Abbreviations ABA abscisic acid - PA phaseic acid - GA gibberellin     

Molecular interactions between light and hormone signaling to control plant growth

As sessile organisms, plants modulate their growth rate and development according to the continuous variation in the conditions of their surrounding environment, an ability referred to as plasticity. This ability relies on a web of interactions between signaling pathways triggered by endogenous and environmental cues. How changes in environmental factors are interpreted by the plant in terms of developmental or growth cues or, in other words, how they contribute to plant plasticity is a current, major question in plant biology. Light stands out among the environmental factors that shape plant development. Plants have evolved systems that allow them to monitor both quantitative and qualitative differences in the light that they perceive, that render important changes in their growth habit. In this review we focus on recent findings about how information from this environmental cue is integrated during de-etiolation and in the shade-avoidance syndrome, and modulated by several hormone pathways—the endogenous cues. In some cases the interaction between a hormone and the light signaling pathways is reciprocal, as is the case of the gibberellin pathway, whereas in other cases hormone pathways act downstream of the environmental cue to regulate growth. Moreover, the circadian clock adds an additional layer of regulation, which has been proposed to integrate the information provided by light with that provided by hormone pathways, to regulate daily growth.     

Gibberellins and <Emphasis Type="Italic">N</Emphasis>-(2-chloro-4-pyridyl)-<Emphasis Type="Italic">N′</Emphasis>-phenylurea improve retention force and reduce water core in pre-mature fruit of Japanese pear cv. Housui

A study of the effect of a gibberellin A₃ + A₄ mixture (GAs) on pre-harvest fruit drop of Japanese pear cv. Housui is reported. The GAs was applied alone or in combination with N-(2-Chloro-4-pyridyl)-N′-phenylurea (CPPU) in a lanolin paste to the abscission zone at the spur-end of the pedicel. The results showed that the GAs and CPPU combination treatment increased the pedicel–spur retention force relative to that of the untreated controls. Histological studies showed an accelerated rate of cambium division and the development of secondary xylem in the abscission zone near the spur-end of pedicels treated with the GAs plus CPPU paste, which delayed the formation of the abscission zone. Fruit quality (sugar, acid, firmness, color) was not adversely affected by the application of GAs plus CPPU, although the application of GAs alone promoted ripening. In contrast, the addition of CPPU to the two GAs delayed fruit ripening, which was measured as ethylene efflux. All treatments were without adverse effects on return bloom, measured as bud size. The CPPU plus GAs treatment also suppressed the incidence of water core, whereas the application of the GAs alone accelerated water core in this water core susceptible pear variety.