脱落酸与向日葵顶端优势关系的研究

本文选用顶端优势程度不同的两个品种向日葵,进行了外源脱落酸的处理实验和内源脱落酸含量的测定,从而对“顶端产生的生长素是通过诱导植物组织内产生或者使其保持有较高水平的脱落酸,由此对侧芽的生长起抑制作用”的假说进行了验证。结果则表明,节内脱落酸的含量及其变化与向日葵的顶端优势无关。     

去除顶端优势对菊芋器官C、N、P化学计量特征的影响

以不同时期顶端优势去除处理的菊芋为研究对象,通过测定根、茎、叶、花和块茎等器官C、N、P含量,计算C∶N、C∶P和N∶P比值,探讨顶端优势去除对菊芋各器官C、N、P化学计量特征的影响规律。结果表明:各器官之间C含量高低顺序没有因去顶而改变,氮和磷含量高低顺序因去顶而表现出不同的大小关系;顶端优势去除提高了茎秆、块茎和分枝的C含量,除最后一次顶端优势去除提高了叶片C含量,其它顶端优势去除时间均降低了叶片含量;顶端优势去除降低了根系、茎秆和块茎N含量,提高了分枝和花的含N量;顶端优势去除提高了叶片和块茎的含P量;C∶N范围为24.15—153.75、C∶P范围为118.87—2265.72、N∶P范围为2.46—24.05,N∶P平均值为10.67,说明菊芋生长主要受N元素的限制。     

不同环境条件下向日葵油及脂肪酸含量研究

试验在巴基斯坦Arid农业大学进行,于2001年春、秋两季分别调查向日葵杂交种的油和脂肪酸含量,其中5个向日葵杂交种按完全随机区组设计,春向日葵在3月播种,6月收获;秋向日葵在8月播种,11月收获。调查结果表明,油和油酸的含量,春向日葵比秋向日葵高;软脂肪酸和亚油酸含量,秋向日葵比春向日葵高。因此,依据油和油酸的含量来推断,春向日葵比秋向日葵有优势;从亚油酸角度判断,秋向日葵比春向日葵更有优势。     

植物的顶端优势现象

植物主茎顶芽生长能抑制侧芽生长的现象称为顶端优势。它是植物器官相关性的一种表现。经常看到有些向日葵的顶端优势很强,它们的顶端只长出一个大花盘来。它们的顶端一旦被除去或受病虫害侵染后死亡,上面的一个或几个侧芽就代替顶芽的地位而长出一个或几个小花盘来。     

真菌中脱落酸生物合成代谢关键酶的初步研究*

应用逆转录PCR(RT-PCR)技术测定脱落酸产生菌Botrytis cinerea 3-羟-3-甲基戊二酰CoA(HMG-CoA)还原酶mRNA含量,结果表明经诱变筛选得到的脱落酸高产菌HMG-CoA还原酶含量显著高于野生菌,提示HMG-CoA还原酶可能为真菌ABA生物合成的关键酶。     

低温胁迫下凤眼莲叶片的适应——脱落酸和可溶性蛋白质含量升高

本文报道低温胁迫下风眼莲叶片脱落酸(ABA)、可溶性蛋白质和水势的测定结果。低温胁迫时脱落酸和可溶性蛋白质含量远高于对照,(前者含量最高可达对照的4倍,后者可达到对照的2.75倍),而且脱落酸和蛋白质含量随温度降低而升高。蛋白质的生物合成抑制剂亚胺环己酮证明,可溶性蛋白质含量升高,原因是有部分是新合成的。在各种低温处理下获得了几乎相同于对照的叶片水势。我们推测:低温胁迫下,脱落酸水平的相应变化不是由于低温诱导水分胁迫所致,而是低温胁迫本身诱导。     

蚕豆叶片和保卫细胞中脱落酸含量的日变化

用双层固相抗体酶联免疫加酶循环放大的超微定量分析测定蚕豆叶片和保卫细胞脱落酸含量日变化的结果表明,在非胁迫的正常生长条件下,蚕豆叶片中脱落酸含量有小的变化,和一天中气孔导性变化的相关性不甚明确;但保卫细胞质外体脱落酸含量有显著的日变化,且和叶片气孔导性有一定的相关性,     

真菌中脱落酸生物合成代谢关键酶的初步研究

应用逆转录PCR(PT-PCR)技术测定脱落酸产生菌Botrytis cinerea 3-羟-3-甲基戊二酰CoA (HMG-CoA)还原酶mRNA含量,结果表明经诱变筛选得到的脱落酸高产菌HMG-CoA还原酶含量显著高于野生菌,提示HMG-CoA还原酶可能为真菌ABA生物合成的关键酶。     

干旱和臭氧浓度升高对元宝枫早生和晚生叶片色素和脱落酸含量的影响

臭氧和干旱是威胁我国北方城市植物生长的两大重要因素。于2012年利用开顶式气室,通过设置4个处理(AW-大气环境和水分充足;AW+60-大气增加60 nL/L臭氧+水分充足;AD-大气+干旱处理;AD+60-大气增加60 nL/L臭氧+干旱处理),开展了大气臭氧浓度升高(以下简称"臭氧")和干旱对元宝枫秋季变色期主要色素含量及脱落酸(ABA)含量的影响研究。结果表明:(1)早生叶在臭氧处理后,总叶绿素和类胡萝卜素分别下降了21%和29.6%、花青苷和类黄酮相对含量显著升高了34.1%和7.3%、脱落酸含量增加了19.8%。干旱处理后,早生叶总叶绿素显著下降了18.7%、花青苷和类黄酮相对含量分别显著升高了37%和7.4%、脱落酸含量显著升高了13%。叶片的上述生理变化将会导致叶片提前变红、叶片早衰和提前脱落。(2)晚生叶在干旱处理后总叶绿素含量减少了18.8%,脱落酸含量增加了33.4%,臭氧以及与干旱共同处理未对晚生叶产生显著影响。(3)臭氧和干旱共同处理后,早生叶总叶绿素含量、花青苷和叶片脱落酸含量存在显著交互作用,交互作用缓解了叶片总叶绿素的下降和花青苷的上升,但未缓解叶片脱落酸含量的增加。综上,早生叶和晚生叶对臭氧和干旱处理的响应不同,早生叶对臭氧处理响应大于晚生叶,而晚生叶对干旱更敏感。臭氧和干旱处理均加速了叶片衰老,二者共同处理后叶片脱落风险增加。     

脱落酸的发酵法生产及应用

脱落酸是重要的植物激素之一,可以增强作物对环境逆因子如干旱、寒冷等的抵抗能力,在抵抗农业自然灾害、植树造林、生态植被建设、城市园林绿化等领域有广阔的应用前景.施用脱落酸可减少化学农药的使用,保护自然环境.本文概述了脱落酸生产和应用方面的研究进展,包括产生菌的筛选、诱变、外施脱落酸在提高作物抗逆性上的应用,以及脱落酸抗肿...     

Does ABA in the Xylem Control the Rate of Leaf Growth in Soil-Dried Maize and Sunflower Plants?

Maize (Zea mays L.) and sunflower (Helianthus annuus L.) plantswere grown in large volumes of soil and leaf growth rate wasmonitored on a daily basis. Half the plants were given a soildrying treatment and when they showed a significant restrictionof growth rate (compared to both their daily growth rate beforedrying and the average growth rate of well-watered plants onthe same day), leaf water relations were measured and xylemsap was extracted using several techniques. There was a significant negative log-linear relationship betweenthe rate of leaf growth and the concentration of ABA in thexylem for both species. There was no clear relationship betweenleaf growth rate and leaf water potential or turgor for eitherspecies. Assessment of different methods for sampling xylemsap suggests that exudates collected from stem stumps or samplescollected by pressurizing the whole root system are suitablefor estimating ABA concentration in xylem, at least with largeplants of maize or sunflower, provided the first few hundredcubic millimetres of collected sap are used for the assay. Centrifugationof sections of stems resulted in dilution of ABA in the xylemsap with sap squeezed from parenchyma tissue. This is because,at least in plants subjected to mild soil drying, the concentrationof the ABA in the xylem is far higher than that in the cellsap of stem tissue. Results support the proposal that ABA plays a major role asa chemical signal involved in the root-to-shoot communicationof the effects of soil drying. The non-hydraulic restrictionof leaf growth by a chemical signal can be explained by theextra root-sourced ABA in the xylem and may be an importantcomponent of the modification of growth and development whichresults from prolonged soil drought. Key words: Soil drying, ABA, leaf growth, Zea mays L., Helianthus annuus L.     

Immunological estimation of growth regulator distribution in phototropically reacting sunflower seedlings

The distribution of immunoassayable xanthoxin (XA), abscisic acid (ABA) and indole-3-acetic acid (IAA) in all parts of sunflower ( Helianthus annuus L.) seedlings was determined. During the course of phototropic curvature, including the lag phase (5 min), the distribution of these growth regulators was analyzed in the illuminated and shaded side of the hypocotyl, as well as in the peripheral and central tissues. All three growth regulators showed no detectable asymmetries between the illuminated and shaded hypocotyl halves during the lag phase and early phototropic curvature. Also, no indication for an exchange of XA, ABA or IAA between the peripheral and central tissues was observed. Partial removal of the peripheral cell layers revealed that changes in the growth properties of this tissue, preferentially at the illuminated side of the hypocotyl, are required for the phototropic reaction. Complete removal of the peripheral cell layers abolishes the phototropic response. In dark-incubated, green sunflower seedlings, the loss of sensitivity to phototropic stimulation is correlated with decreasing levels of IAA immunoreactivity, whereas no changes in the levels of ABA- and XA immunoreactivity were recorded. The findings are discussed with respect to the involvement of ABA, XA and IAA in phototropic reactions of green dicotyledonous shoots.     

Effect of abscisic acid on exudation from deficient and aged sunflower roots

The effect of abscisic acid (ABA) was observed on exudation from roots of sunflower ( Helianthus annuus L. cv. Habad) plants whose mineral nutrition was cut off or which were deprived of K⁺ or NO⁻₃ for 90 h prior to excision. In spite of a marked decrease in exudation rate, the magnitude of the promotive effect of ABA on both volume flow and release of ions to the xylem was similar to that obtained in roots of plants grown in full nutrient solution. Application of ABA to the medium at different times after excision increased the promotive effect of ABA as the time from excision increased. The magnitude of the ratio ABA-treated/control in roots which were treated 74 h after excision was twice that in freshly-excised roots. The effect of ABA lasted up to 50 h and during that period it followed the endogenous rhythm in exudation from the control roots. It is concluded that since a steady promotive effect of ABA persists under a variety of experimental conditions, this may be considered a genera! phenomenon in sunflower roots.     

Stomatal closure is induced rather by prevailing xylem abscisic acid than by accumulated amount of xylem-derived abscisic acid

We have studied the stomatal response in relation to the xylem-derived abscisic acid (ABA) accumulation in sunflower leaves. When ABA was introduced into detached leaves of the sunflower through xylem flux, stomatal conductance was regulated, water flux was changed as a result and at the same time the xylem-derived ABA was metabolised in the leaves. We computed the xylem-derived ABA accumulation in the leaves as a function of time by taking into account the variation of ABA flux into the leaves (the product of water flux and ABA concentration) and a continuing ABA metabolism. We found that ABA accumulation was rapid during an initial lag phase, much slowed down during the decreasing phase of stomatal conductance, but still substantial when stomatal conductance reached a new stable state. The results show a poor link between the kinetics of ABA-induced stomatal closure and the xylem-derived ABA accumulation. Xylem-derived ABA was metabolised rapidly in the leaves. Tetcyclacis, as an inhibitor, substantially inhibited this process. Two hours after ABA was fed into a leaf, about 70% of the fed ABA was metabolised, but when tetcyclacis was added into the feeding solution, less than 30% of ABA was metabolised, even after 24 h of incubation. The inhibition of ABA metabolism by tetcyclacis did not lead to more stomatal closure, which was still concentration-dependent. Since the accumulation of xylem-derived ABA was enhanced substantially by the presence of tetcyclacis, these results strongly indicate that stomata mainly respond to the prevailing ABA concentration in the xylem stream, rather than to the accumulated amount of xylem-derived ABA in the leaves.     

Characterization of a sunflower (Helianthus annuus L.) mutant,deficient in carotenoid synthesis and abscisic-acid content,induced by in-vitro tissue culture

Genetic variation induced by tissue culture has been characterized in many species. The present study was conducted to genetically and phenotypically characterize an albino mutant in sunflower induced by in-vitro culture. A single recessive gene defective in carotenoid biosynthesis eventually leads to a chlorophyll loss due to photobleaching, absence of seed dormancy, and a low level of endogenous abscisic acid (ABA) in cotyledons and leaves. Further characterization has shown that the endogenous level of the hormone does not increase after drought stress and that the mutation prevents anthocyanin synthesis.     

Effect of drought, on transport and metabolism of abscisic acid in aeroponically grown Helianthus annuus

The effect of drought on transport and metabolism of radioactive abscisic acid (ABA) in roots and shoots of sunflower ( Helianthus annuus L. cv. Russian) was observed. Radioactivity from ABA moved freely all over the plants. Young shoot tissues, such as the growing apical bud or axillary buds released from apical dominance, were strong sinks for ABA. Mature tissues were effective exporters. Drought-induced alterations in the pattern of transport of radioactivity do not appear to be a major factor in the control of drought-induced changes in ABA levels. Metabolism of ABA occurred in all organs examined in stressed and unstressed plants. Labelled ABA and its metabolites moved in the xylem. Drought altered the quantity of radioactive metabolites and reduced the amount of radioactive ABA in extracts from the stressed plants.     

Changes of free and conjugated abscisic acid and phaseic acid in xylem sap of drought-stressed sunflower plants

Abscisic acid (ABA), conjugated abscisic acid, phaseic acid (PA), and conjugated phaseic acid were determined by enzyme-linked immunosorbent assay (ELISA) and gas chromatography (GC) in xylem sap of well-watered and drought-stressed sunflower plants. Conjugated ABA and conjugated PA were determined indirectly after chemical or enzymatic hydrolysis. Conjugated ABA was found to be the predominant ABA metabolite in xylem sap. In xylem sap from well-watered plants at least five, and in sap from drought-stressed plants at least six alkaline hydrolysable ABA conjugates were found. One of them corresponds chromatographically (HPLC) with abscisic acid glucose ester (ABAGE). Under drought conditions the concentrations of ABA, alkaline hydrolysable ABA conjugates, -glucosidase hydrolysable ABA conjugates, PA, and conjugated PA increased. After rewatering the drought-stressed plants, the ABA and the conjugated ABA content decreased. The possible function of the ABA conjugates in the xylem sap as a source of free ABA is discussed.     

Effect of osmotic stress on abscisic acid levels in xylem sap of sunflower (Helianthus annuus L.)

Summary Addition of an osmoticum (-12 bars) to the rooting medium of sunflowers (Helianthus annuus L.) caused an increase in the level of abscisic acid (ABA) present in xylem exudate subsequently collected from cut shoots. Using tall and dwarf plants it was shown that there was a time lag in the appearance of increased levels of ABA in tall plants when compared with dwarf plants. The results indicate that the leaves, rather than the roots are the site of synthesis of ABA present in the xylem sap of osmotically stressed sunflower plants.Abbreviation ABA abscisic acid     

Stress induction and antimicrobial properties of a lipid transfer protein in germinating sunflower seeds

Nonspecific lipid transfer proteins (nsLTPs) belong to a large family of plant proteins whose function in vivo remains unknown. In this research, we studied a LTP previously isolated from sunflower seeds (Ha-AP10), which displays strong antimicrobial activity against a model fungus. The protein is present during at least the first 5 days of germination, and tissue printing experiments revealed the homogeneous distribution of the protein in the cotyledons. Here we report that Ha-AP10 exerts a weak inhibitory effect on the growth of Alternaria alternata, a fungus that naturally attacks sunflower seeds. These data put into question the contribution of Ha-AP10 as an antimicrobial protein of direct effect on pathogenic fungus, and rather suggest a function related to the mobilization of lipid reserves. We also show that the levels of Ha-AP10 in germinating seeds increase upon salt stress, fungal infection and ABA treatment, indicating that it somehow participates in the adaptative responses of germinating sunflower seeds.