The Influence of Light Quality on Levels of Ahscisic Acid in Tomato Plants, and Evidence for a Novel Abscisic Acid Metabolite

Tomato plants were grown in growth cabinets under two different light sources. One source consisted of white and red fluorescent tubes (Red cabinet), while the second consisted of both tungsten filament and fluorescent lamps (Far red cabinet). Energy fluence rates were adjusted to give equal photosynthetic rates in the two cabinets. Extension growth was approximately three times greater in the Far-red cabinet. No difference could be detected in abscisic acid (ABA) levels in leaves or petioles of plants grown under the two light regimes, but levels were 40–90% greater in stems of the slower growing plants illuminated with fluorescent light only. Exogenously applied ABA effectively reduced the growth rate of the plants in the Far-red cabinet to that of plants in the Red cabinet. However, it was shown that light-induced changes in growth rates occurred before any change in endogenous ABA could be demonstrated, thus precluding a role for ABA in the initial response to a change in light quality. The changed ABA levels appeared to be the result of a modified pathway of ABA degradation. Evidence is presented for a novel metabolite of ABA which yields free ABA on basic hydrolysis.     

Opposing effects of abscisic acid on senescence of rose flowers

Abscisic acid induced stomatal closure and reduced water lossof cut rose flower shoots bearing leaves. Its effect was verypronounced when these flowers were exposed to atmospheric stressconditions. Even short-term treatments (24 hr) with ABA extendedthe longevity of the flowers. However, in a stomata-less system(leafless flower shoots), or in leafy shoots held in darknesswhen all stomata were closed, ABA enhanced aging of the flowersand some biochemical processes associated with it (RNase activityand reduction in protein content). ¹Agricultural Research Organization, The Volcani Center. ²Present address: Dept. of Environmental Horticulture, Universityof California, Davis, Calif. (Received May 2, 1974; )     

The Relationship between Flower Abortion and Endogenous Auxin Content of Rose Shoots

The amount of endogenous growth substances in stem, flowers and leaves of rose plants grown under different temperature and light conditions has been determined. It appeared to be two main growth promoting factors in the acidic fraction of the ether extract. One of them is assumed to be an auxin, probably indol-3yl-acetic acid (IAA); the other is not identified. The level of auxin was much higher in extracts from shoots grown at high temperature than in shoots grown at low temperature. Increasing light intensity also seemed to increase the auxin content of the shoots. Shoots which developed after a high cut back of the rose stem had a higher auxin content than shoots which developed after a low cut back. These findings are discussed in relation to the effect of temperature, light intensity and cut back practise on blind shoot formation in roses. The result of these investigations strongly indicate that abortion in roses is promoted by a low auxin level in the shoots.     

Proline level is partly under the control of abscisic acid in canola leaf discs during recovery from hyper-osmotic stress

The relationships between the changes induced in abscisic acid (ABA) and proline contents were investigated in canola ( Brassica napus L.) leaf discs (CLDs) subjected to sequential hyper- and hypo-osmotic treatments. Changes in ABA content were found to precede that of proline, suggesting that ABA could exert regulatory effects on both osmo-induced proline accumulation and its subsequent mobilization during recovery. When exogenously supplied in the light during recovery, ABA caused inhibition of the apparent rate of proline mobilization with an I50 of about 20 μ M . Under dark conditions, the ABA effect was not observed. This is in accordance with the fact that this effect could be suppressed in the light while using photosynthesis inhibitors. The ABA effect was partly restored under dark conditions when the CLDs were supplied with NADPH at high concentration. Under both conditions, ABA exerted its effect when supplied together with cycloheximide, suggesting that it does not rely on protein synthesis. When turgid CLDs, which heavily absorbed exogenously supplied l -proline, were incubated in the light on the reference medium with ABA, proline mobilization was also restricted, provided ABA was supplied during the period of proline uptake. Surprisingly, in CLDs that had recovered their full turgor after application of successive hyper- and hypo-osmotic treatments, application of ABA led to a very high accumulation of proline. In contrast, in freshly cut turgid CLDs incubated in presence of ABA, the basic proline level was only weakly enhanced. Thus, the apparent inhibitory effect of ABA on proline mobilization could be mediated through both an activation of biosynthesis and an inhibition of catabolism of this amino acid via light-dependent processes that remain to be elucidated.     

外源NO对瓶插期间的月季切花中内源激素含量的影响

以硝普钠（SNP）为一氧化氮供体,研究NO及其清除剂2-苯基-4,4,5,5-四甲基咪唑啉-1-羟-3-氧（PTIO）影响月季瓶插期间的生理指标和内源激素含量的结果表明：0.1mmol.L-1SNP释放的NO抑制月季切花瓶插期间花瓣中内源乙烯释放速率和ABA含量的升高,延缓IAA含量的下降,并保持组织中相对较低的ZR和GA水平。PTIO则可促进花瓣中的乙烯、ABA、ZR和GA含量的升高和IAA含量的下降。     

Changes in abscisic acid and phenols during flower development in two diverse species of rose

Changes in endogenous abscisic acid (ABA) and phenols were determined in petals of two diverse species of rose, viz., Rosa damascena Mill and Rosa bourboniana Desport during flower development. A progressive increase in free ABA was observed during flower development till full bloom in both the species with higher content of free ABA in Rosa damascena. While bound ABA level increased in Rosa damascena till stage 6, in Rosa bourboniana it continued to increase till full bloom. Acidic phenols increased slowly in both the species till stage 4, but sharply afterwards and no significant differences were noticed during full bloom period. Bound phenols content was higher in Rosa damascena during full bloom period. The significance of these changes in relation to flowering in the two diverse species of rose is discussed.     

Growth and photosynthesis of Chinese cabbage plants grown under light-emitting diode-based light source

We compared growth and the content of sugar, protein, and photosynthetic pigments, as well as chlorophyll fluorescence parameters in 15- and 27-day-old Chinese cabbage (Brassica chinensis L.) plants grown under a high-pressure sodium (HPS) lamps or a light source built on the basis of red (650 nm) and blue (470 nm) light-emitting diodes (LEDs) with a red to blue photon ratio of 7: 1. One group of plants was grown at a photosynthetic photon flux (PPF) level of 391 ± 24 μ mol/(m² s) (normal level); the other, at a PPF level of 107 ± 9 μ mol/(m² s) (low light). Plants of the third group were firstly grown at the low light and then (on the 12th day) transferred to the normal level. When grown at the normal PPF level, the plants grown under LEDs didn’t differ from plants grown under HPS lamps in shoot fresh weight, but they showed a lower root fresh and dry weights and the lower content of total sugar and sugar reserves in the leaves. No differences in the pigment content and photosystem II quantum yield were found; however, a higher Chl a/b ratio in plants grown under LEDs indicates a different proportion of functional complexes in thylakoid membranes. The response to low light conditions was mostly the same in plants grown under HPS lamps and LEDs; however, LED plants showed a lower growth rate and a higher nonphotochemical fluorescence quenching. In the case of the altered PPF level during growth, the plant photosynthetic apparatus adapted to new conditions of illumination within three days. Plants grown under HPS lamps at a constant normal PPF level and those transferred to the normal PPF level on the 12th day, on the 27th day didn’t differ in shoot fresh weight, but in plants grown under LEDs, the differences were considerable. Our results show that LED-based light sources can be used for plant growing. At the same time, some specific properties of plant photosynthesis and growth under these conditions of illumination were found.     

ABA synthesis in protoplasts of different origin in response to osmotic stress

All the protoplasts analysed in this study whatever the original plant material were able to accumulate ABA under osmotic stress. The time course of ABA accumulation strongly differed according to the plant material. In both rose petal or Amaranthus leaf protoplasts, the increase in ABA level was significant but transient. Protoplasts prepared from Amaranthus cell suspensions behaved differently, showing a late and durable accumulation of ABA. Similar patterns of changes in ABA accumulation were observed in the original plant material under osmotic stress. A pretreatment of plant material by fluridone induced a strong inhibition of ABA accumulation whatever the origin of protoplasts was. This result suggests that ABA could be synthesised via the carotenoid pathway in the absence of the cell wall.     

Abscisic acid content in the root hemiparasiteMelampyrum arvense L. before and after attachment to the host plant

The content of abscisic acid (ABA) in abaxial leaf epidermis of the host (Capsella bursa pastoris) and the unattached hemiparasiteMelampyrum arvense showed diurnal changes. ABA content increased during the light period and declined rapidly upon the darkening of leaves. In an attached hemiparasite the content of ABA in the epidermis was maintained at an almost constant level irrespective of the diurnal cycle. As compared with the maximum level in the host, at the end of the light phase the content of ABA in abaxial epidermis constituted about 70 % and 164 % in the unattached and attached hemiparasite, respectively. No significant changes in ABA content were recorded in adaxial epidermis. In all the samples abaxial/adaxial epidermis ABA content ratio was about 3.6:1 in light phase. In darkness this ratio decreased to about 1.1:1 in the host and the unattached hemiparasite and did not show significant change after attachment. ABA content ratio in mesophyll was 1:0.7:1.5 for the host, the unattached, and attached hemiparasite, respectively. In comparison with the host the concentration of ABA in xylem sap of the hemiparasite constituted about 31 % and 152 % for the unattached and attachedM. arvense, respectively.     

多效唑对月季切花衰老的影响

本文研究了用多效唑处理的月季切花在瓶插期间的形态、生理变化,结果表明,多效唑能明显地缓解月季切花水分胁迫,改善体内水份平衡,促进切花开放,增加花朵鲜重和花径,抑制花瓣溶质外渗,延缓切花呼吸速率的下降和蛋白质降解的速率,从而延缓切花衰老。     

Correlative Changes in Phytohormones in Relation to Senescence Processes in Rose Petals

A comparative study of the level of abscisic acid (ABA) and cytokinin and of ethylene production by rose (Rosa sp.) petals of the short-lived cultivar Golden Wave (Dr. Verhage) and the long-lived cultivar Lovita was conducted. In both cultivars, the level of ABA increased as the flowers aged; it was higher in Golden Wave in all developmental stages tested. Ethylene production by cut flowers of the two cuitivars remained low for a short time concomitant with development and then increased sharply. The rise in ethylene production occurred after 3 and 4 days in Golden Wave and Lovita, respectively. Cytokinin level increased as the flower started to open and then decreased to a low level. The significance of these changes in relation to maturation and senescence of rose petals is discussed.     

The Water Balance of Cut Rose Flowers

A sharp decline in water potential of petal tissue associated with wilting of cut rose flowers is described. Such a decline did not develop in senescing intact flowers. A circadian rhythm in water absorption by cut flowers was observed. The decline in fresh weight observed in the last phase of the vase life of cut flowers occurred earlier in a short-lived cultivar than in a longer-lived one. A decline in potential conductivity to water was observed with time in stems of cut roses. Concomitantly cellulase activity increased after cutting. Flowers held in cellulase solution wilted earlier than the controls. However, no difference was found in these two parameters between two cultivars differing in their longevity. The difference in longevity between the two cultivars was large especially under conditions promoting high transpiration rates, and was narrowed when flowers were either held in mild conditions, or the leaves were stripped off. Although stomates were equally open in intact flowers of the two cultivars, in cut flower shoots of the short-lived cultivar stomates were more widely open. In accordance transpiration rates were higher, and wilting occurred earlier in the short-lived cultivar than in the long-lived one. It is concluded that the earlier wilting of cut flowers of the short-lived cultivar is mainly due to lower ability to close stomates in response to water stress conditions, and not to earlier formation of vascular blockage.     

High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leaves

Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and β‐glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and β‐glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA‐glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low β‐glucosidase activity converting ABA‐GE to ABA. Continuous lighting (24 h) resulted in low levels of β‐glucosidase activity irrespective of RH, indicating that a dark period is essential to activate β‐glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that β‐glucosidase is a key enzyme regulating the ABA pool in rose plants.     

茭白生育过程中地上各部位内源激素的含量变化

以两个茭白品种为试材,测定了植株茎蘖生育过程中地上各部位主要激素及肉质茎膨大过程中的干重变化。结果显示：茭白植株生育过程中各部位的激素以玉米素及玉米素核苷(Z ZR)的含量最高,生长素(IAA)其次,赤霉素(GA3)和脱落酸(ABA)含量很低;在各部位间总体以茎尖最高,叶鞘其次,叶片最低。其中Z ZR含量在肉质茎膨大前即已明显上升,膨大开始后显著下降;IAA含量在肉质茎膨大后期至末期才出现下降;叶片内ABA含量在肉质茎膨大前即开始上升,叶鞘内ABA．含量在肉质茎膨大后期上升,茎尖内则无明显变化;各部位GA2含量在整个生育期内无明显变化。肉质茎的干重增加也与其Z ZR含量下降密切相关。认为Z ZR是刺激肉质茎膨大的关键激素。品种间差异表现为各部位激素含量及其变化有一定差异,尤其是肉质茎膨大阶段差异比较明显。     

Carotenoid composition and down regulation of photosystem II in three conifer species during the winter

Seedlings and coppice shoots of Betula pubescens Ehrh. were grown under controlled conditions designed to simulate the annual growth cycle, and a water stress was introduced during the short day (SD). Alleviation of hud dormancy after increasing periods at chilling temperatures was tested under long day (LD) conditions. Abscisic acid (ABA) was analysed in leaf and bud samples by gas chromatography-mass spectrometry using [²H₄]ABA as the internal standard. Elongation growth of coppice shoots was faster than that of seedlings under both LD and SD conditions, while the final growth cessation occurred in a similar manner and was not affected by water stress, which significantly reduced growth rate in both plant types. Bud dormancy gradually decreased with increasing length of chilling, starting from the basal parts of the plant axis. Water stress did not retard hudhurst. but rather improved it in the chilled coppice shoots and in the non-chilled and partially chilled seedlings. Water content of buds was higher in coppice shoots than in seedlings, but after exposure to SD. it gradually decreased to 45% in both plant types and was not affected by water stress or chilling. The ABA level in both leaves and buds increased during SD treatment and was" enhanced by water stress. No clear differences in bud ABA level were found between the seedlings and coppice shoots under SD conditions, although coppice shoots had less ABA during the preceding LD conditions. There was, in general, no clear effect of chilling on bud ABA level. Budbursl in chilled, single-node cuttings was inhibited by external ABA treatment, which raised the internal ABA levels 10 to 150 times above normal. The observed correlation between ABA level and water content in buds during induction of dormancy under SD and water stress conditions indicates a possible role for ABA in the regulation of dormancy.     

Early Release of ABA from Cell Walls During Rose Petal Protoplast Isolation

During the isolation of rose petal protoplasts, two successivetransient abscisic acid (ABA) accumulations were detected whendigest medium and tissue slices were assayed simultaneously,using polyclonal antibodies raised against (+)-ABA. Late accumulation,occurring after more than 1 h of incubation, was observed, whetherenzymes were present or not, in a hyperosmotic medium. Veryearly accumulation, occurring at a maximum of 15 min after thebeginning of incubation, was observed only in the presence ofcellulolytic and pectinolytic enzymes. The ABA level could beincreased by the addition of tetcyclacis, an inhibitor of mono-oxygenaseknown to delay ABA oxidation. The need for cell wall digestingenzymes to observe this first ABA increase suggested that itwas due to a release from the cell wall. Analysis by radioimmunoassay(RIA) and high performance liquid chromatography (HPLC) showedthat ABA and another non-acidic immunoreactive compound werereleased from purified cell walls by the same enzymes. Key words: ABA, cell wall, protoplast, rose petal     

Relative control potential of abscisic acid, carbon dioxide and light in responses of Phaseolus vulgaris stomata

We outline a theoretical framework for comparing the relative effectiveness of hormonal and other factors in the control of physiological responses. This involves determining a 'baseline' set of conditions, then adjusting each factor in turn with the others held constant. The initial rate of response to each change in condition is estimated and compared among factors to arrive at a quantitative indication of control potential under the specified baseline conditions – the control coefficient. The suitability of the stomatal response as a model system for such studies is discussed. A portable infra-red gas analyser was used to investigate the control potential of abscisic acid (ABA), CO₂ and light – measured as photosynthetic photon flux density (PPFD) – over responses of Phaseolus vulgaris L. stomata at baseline conditions appropriate to an unstressed plant under moderate light conditions. The ranking of control coefficients observed under these conditions was light>CO₂>ABA. The control coefficients of CO₂ and ABA were 0.28 and 0.11 times that of light, respectively. These results are discussed in relation to the sensitivity of the plant material and the experimental conditions. Implications for a hormonal role for ABA in the control of stomatal movements are considered. We conclude that this method can provide valuable information concerning the relative control potential of hormonal and other influences in the context of differences in baseline conditions and in relation to changes in sensitivity of plant material.     

Contrasting photo- and thermoperiod-induced changes in abscisic acid and lipid contents in leaves of mungbean seedlings

Seedlings of Phaseolus aureus ROXB were grown under 12/12 h light/dark cycles with the light period at 32.5°C and darkness at 10°C (normal conditions N) or with light at 10°C and darkness at 32.5°C (inverse conditions, I). I-conditions affected the level of chlorophyll and carotenoids (very low), monogalactosyldiacylgycerol (low) and phosphatidylinositol (high) in the leaves. Leaves of I-seedlings showed a sharp and durable decline of relative water content during the low temperature phase. For the N-seedlings, loss of water was restricted to the end of this period. The loss of water was accompanied by visible symptoms of wilting at specific times of day. Although the pigment content remained nearly unchanged, ABA content of leaves of both N-and I-seedlings increased during water stress. Upon return to the warm period, ABA level continued to increase after the leaves had regained turgor, this 'after stress'increase being more pronounced in the leaves of I-seedlings. Exogenous application of ABA induced a slight increase in the content of phospholipids in N- and I-leaves and a decrease in free fatty acids, whereas monogalactosyldiacylglycerol content was significantly reduced in N-leaves after application of ABA. Upon transfer of I-plants to 20°C for 12 h during the light period, pigment and chloroplastic lipid content increased rapidly whereas upon a further exposure to 10°C in light, pigments and especially monogalactosyldiacylglycerol were lost. The control of pigment and lipid metabolism and the role of ABA during chilling stress are discussed.     

Endogenous ABA content in relation to maturation of somatic embryos in <Emphasis Type="Italic">Tulip</Emphasis>a (L.) ‘Apeldoorn’ cultures

The aim of the present study was to estimate the endogenous abscisic acid (ABA) content in tulip ‘Apeldoorn’ torpedo and mature somatic embryos. Moreover, the effect of exogenous ABA and/or its inhibitor fluridone on somatic embryo maturation and conversion into plantlets was investigated. Torpedo-stage somatic embryos were subcultured on media containing 5 μM of picloram and 1 μM of 6-benzyl-aminopurine (BAP)—control, and combinations of ABA (0 or 10 μM) and/or fluridone (0 or 30 μM) for 1 week. Then, the torpedo embryos were transferred to a maturation medium containing 0.25 μM of α-naphthaleneacetic acid (NAA) and 2.5 μM of BAP, without ABA and fluridone treatment, and cultivated under darkness or light for ten weeks. Endogenous ABA content (first time measured in tulip somatic embryos) was evaluated by ELISA test. The obtained results revealed that the highest level of endogenous ABA, at 17.45 nmol g^?1 dry weight (DW), was recorded in torpedo-stage of tulip embryo development, only after 1 week of ABA treatment, and was nearly 10 times higher in comparison with the control. Simultaneous addition of ABA and fluridone to the medium resulted in the lowering of the ABA concentration to 9.58 nmol g^?1 DW. During ten weeks of maturation of the embryos, the endogenous ABA content in mature tissue of tulip somatic embryo considerably decreased to an amount 0.87–1.33 nmol g^?1 DW (irrespective of ABA and fluridone treatment) and did not differ significantly from control (0.59 nmol g^?1 DW). Exogenous ABA and fluridone significantly decreased the growth value of fresh weight (FW) of the tulip torpedo-shaped and mature embryos under light conditions. Percentage of the DW of the torpedo embryos treated with exogenous ABA was significantly higher (15.43–17.02) in comparison with the control (10.87). Three to three and a half times more malformed mature embryos were noted under light conditions than in darkness, irrespective of ABA and fluridone treatment. The highest percentage of mature embryos forming shoots (conversion) was observed under light conditions in the control and after fluridone treatment (26 and 20%, respectively).