Studies on the Active Changes of GA3 and Cytokinins During Development and Ripening in Seabuckthorn Fruits

The phenological stages in seabuckthorn (Hippophae rhamnoides L. Subsp. sinensis Rousi and H. thibetana Schlechted) distributed naturally over an area of Wushao ridge were observed. The changes in levels of endogenous phytohormones GA3, iPA, zeatin, IAA and ABA were investigated systematically during development and ripening periods in the two sorts of fruits. The results showed that two peak values of GA3 level in seeds were detected (in 105—109 days and 128--132 days after anthesis). The first peak value of isopentenyl adenine (IPA) in seeds was determined in 92--96 days when the fruit was starting to change its colour and just right now the zeatin first appeared. The iPA content reached the second peak value in 127-136 days after anthesis during fruit full ripening and beginning to deciduous leaf and the maximum of zeatin in seeds appeared near the same time (in 127 days after anthesis). It was remarkable that the zeatin content in fruit stalk and flesh still was kept on high level, in the meantime the zeatin level in seeds dropped down rapidly. Based on the facts that the time of the first peak value in GA3 and iPA level is close to the date when ABA is first detected, and the date of second peak value in GA3, iPA and IAA is coincident with the time of maximum in ABA and zeatin levels make it reasonable to consider that the balance of phytohormones may be more important than absolute amounts of any single hormone during the periods of fruit development and ripening, and meanwhile it also proved that GA3 and CTK play an important regulatory role in controlling fruit ripening and colour changing process of seabuckthorn fruit.     

Transcriptomes of Fruit Cavity Revealed by De Novo Sequence Analysis in Nai Plum (<Emphasis Type="Italic">Prunus salicina</Emphasis>)

Nai plum (Prunus salicina) is an important fruit crop in China having good taste and flavour. Cavity formation occurring during fruit development affects fruit quality. However, the molecular mechanism underlying cavity formation is unclear. To obtain differential expression profiles of cavity fruit (CF) and non-cavity fruit (nCF) in P. salicina, we sequenced the fruits at different time intervals of 7 days after anthesis (DAA), 21 and 28 DAA, respectively, and 83,869 unigenes, 3811 differentially expressed genes, 22,971 simple sequence repeats and over 14,000 single nucleotide polymorphisms were obtained. Twenty-three differentially expressed genes were selected for verification by qRT-PCR. The contents of phytohormones during fruit development showed that there was a positive relevance between phytohormone contents (IAA, ZR and GA), fruit size and ABA contents in the fruits, whereas there was a negative correlation with ZR, GA and IAA. Lower GA content in fruit before 14 DAA and higher IAA and ZR levels during later developmental stages resulted in cavity appearance. Further studies showed that differential expression of phytohormone-related genes IPT, CKX, YUCCA, GA20ox, GID1, CCS1 was determined at key fruit development stages, which is consistent with content changes of IAA, GA, ABA and ZR. Our results suggest that ABA might inhibit the synthesis of IAA, ZR and GA and cause fruit cavity formation in Nai plum.     

板栗种子发育期间ABA等生理指标与脱水耐性的相关性研究

对板栗种子发育期间胚轴和子叶中部分生理指标的变化以及它们与板栗种子脱水耐性的相关性进行研究.结果表明:随着板栗种子不断发育,在花后80 d胚轴和子叶中ABA、淀粉、可溶性蛋白质量分数同步达到最大值,可溶性糖质量分数达到最低,此时板栗种子的脱水耐性最强,可确定为板栗的最佳采收期.另外,通过相关分析可知,板栗种子在发育期间...     

Induced parthenocarpy—a way of changing the levels of endogenous hormones in tomato fruits (Lycopersicon esculentum Mill.) 1. Extractable hormones

Ethylene, indol-3-acetic acid (IAA), gibberellin-like substances (GAs) and abscisic acid (ABA) were analysed in extracts from normal, seed-containing and parthenocarpic tomato fruits throughout fruit development. Parthenocarpic fruit growth was induced with an auxin (4-CPA), morphactin (CME) or gibberellic acid (GA₃) and compared with that of pollinated control fruits. Fruit growth was only affected by the treatment with GA₃, decreasing size and fresh weight by 60%. The peak sequence of hormones during fruit development was ethylene-GAs-IAA-ABA. Seeded fruits contained the highest levels of IAA and ABA but the lowest levels of GAs. Also, in seeded fruits, a high proportion of IAA and ABA was found in the seeds whereas this was not the case for GAs.Hormone levels of tomato fruits may be successfully, easily and reproducibly altered by inducing parthenocarpic fruit growth and thus eliminating development of seeds which are a major source of hormone synthesis. In spite of markedly changed hormone levels, there was no obvious relationship between fruit growth and extractable hormones per se. However, the results indicate that a high ratio of GAs: auxins is unfavourable for growth of tomato fruits.     

Changes in soluble amino nitrogen,protein, nitrate reductase activity and abscisic acid during development of wheat grain

Trends in the time course, changes in the moisture, soluble amino acids, proline, abscisic acid contents and nitrate reductase activity determined byin vivo method in the developing seeds of wheat were studied. Maximum dry matter augmentation in the seed took place in the period between 10–30 days after anthesis. Per cent moisture and moisture content started declining 15 days and 25 days after anthesis, respectively. Levels of soluble amino acids, proline and nitrate reductase activity were higher during initial stages of seed development, but decreased with increasing magnitude of dehydration and accumulation of abscisic acid (ABA) in the maturing seeds.     

Effect of abscisic acid on the transport of assimilates in barley

The effect of abscisic acid (ABA) on assimilate transport in barley was investigated in two parallel experiments. First, the effect upon [¹⁴C]sucrose transport from the flag leaf to the ear of a single ABA application made at different stages of growth of the fruits was investigated; the effect was measured 24 h after treatment. Second, the effect of a single application of ABA made at the same stages of growth as above on grain weight of the mature plant was investigated. In both types of experiments ABA was applied once to the ear of different plants as an aqueous solution (10^-3–10^-5 M), one to five weeks after anthesis. [¹⁴C] sucrose was applied by means of agar blocks. Parallel to these experiments, the endogenous content of ABA was investigated in the developing grains. When ears were treated with ABA two or four weeks after anthesis, an increase of up to 70% in the ¹⁴C-transport from the flag leaf to the ear was observed within a 24-h period after treatment (short duration experiments). At these growth stages the endogenous concentrations of ABA were low. In sharp contrast, ABA, especially in a concentration of 10^-3 M, decreased ¹⁴C-import from the flag leaf when applied three weeks after anthesis. At this stage the endogenous ABA content had reached its maximum. Long duration experiments with a single application of ABA to the car two weeks after anthesis resulted in a marked increase of weight per thousand kernels. ABA applications made earlier or later than two weeks after anthesis either reduced the grain weight or had no effect. It is concluded that ABA is involved in the regulation of assimilate transport from the leaves to the grains, possibly by influencing the unloading of sieve tubes in the ears. Promotion or inhibition of assimilate import by exogenously applied ABA may depend on the developmental stage of the grains and on the endogenous ABA level.Abbreviations ABA abscisic acid - TKW weight per thousand kernels     

Fruit age and changes in abscisic Acid content, ethylene production, and abscission rate of cotton fruits

The relationships of fruit age, abscisic acid (ABA) concentration, ethylene evolution, and abscission rates were studied in an effort to determine why cotton (Gossypium hirsutum L., cv. Deltapine 16) fruits rarely abscise more than 15 days after anthesis. Because abscission of cotton fruits is increased by conditions that limit photosynthesis, greenhouse-grown plants with fruits of various ages were placed in dim light for 3 days to induce high rates of fruit abscission. Abscission rates, ABA concentrations, and ethylene evolution rates were determined for fruits of various ages. Almost all of the young fruits abscised, but abscission rate declined with age until almost no abscission was observed in fruits that were 15 or more days past anthesis.     

Induction of dormancy during seed development by endogenous abscisic acid: studies on abscisic acid deficient genotypes of Arabidopsis thaliana (L.) Heynh.

Mutant lines of Arabidopsis thaliana (L.) Heynh., which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits (siliquae) than the wild type. Reciprocal crosses of wild type and ABA-deficient mutants showed a dual origin of ABA in developing seeds. The genotype of the mother plant regulated a sharp rise in ABA content half-way seed development (maternal ABA). The genotype of the embryo and endosperm was responsible for a second ABA fraction (embryonic ABA), which reached much lower levels, but persisted for some time after the maximum in maternal ABA. The onset of dormancy correlated well with the presence of the embryonic ABA fraction and not with the maternal ABA. Dormancy developed in both the absence and presence of maternal ABA in the seeds. In this respect maternal ABA resembled exogenously applied ABA which did not induce dormancy in ABA-deficient seeds. However, both maternal and applied ABA stimulated the formation of a mucilage layer around the testa, which could be observed during imbibition of the mature seeds. In the mature state, ABA-deficient seeds germinated in the siliquae on the plant, but only when the atmosphere surrounding the plant was kept at high relative humidity. In younger stages germination in siliquae occurred after isolation from the plants and incubation on wet filter paper. Therefore, it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.     

野生玫瑰果实发育过程中种子的细胞组织结构和内源激素变化对其休眠性的影响

以吉林珲春自然群落的野生玫瑰(Rosa rugosa Thunb.)为试验材料,探究野生玫瑰在果实形成过程中种子的发育及休眠性的形成和变化。选取青果期(1~35 d)、转色期(35~60 d)、红果期(60~75 d)的果实及种子,结合形态学、组织细胞学观察法及高效液相色谱技术,对果实各发育时期的种子形态、种胚及内果皮的发育进行研究,并分析种子内源激素含量变化与果实发育、种子休眠之间的关系。结果表明:果实和种子在青果期(1~35 d)时发育速度最快,种胚在花后24 d发育完全,种子不存在形态休眠。花后24 d内果皮开始沉积木质素并逐渐木质化,种子开始产生机械休眠。种子激素含量的变化与果实的发育、转色及内果皮的木质化密切相关,种子内源GA3和ABA含量在青果期(1~35 d)达到峰值,内源IAA含量在果实转色期(35~60 d)达到最大值,高浓度的ABA含量是种子尚未脱离果实时便已进入生理休眠的主要原因。     

Dormancy and Germination of Abscisic Acid-Deficient Tomato Seeds : Studies with the sitiens Mutant

The role of abscisic acid (ABA) in the dormancy induction of tomato (Lycopersicon esculentum) seeds was studied by comparison of the germination behavior of the ABA-deficient sitiens mutant with that of the isogenic wild-type genotype. Freshly harvested mutant seeds, in contrast to wild-type seeds, always readily germinate and even exhibit viviparous germination in overripe fruits. Crosses between mutant and wild-type and self-pollination of heterozygous plants show that in particular the ABA fraction of embryo and endosperm is decisive for the induction of dormancy. After-ripened wild-type seeds fully germinate in water but are more sensitive toward osmotic inhibition than mutant seeds. Germination of both wild-type and mutant seeds is equally sensitive toward inhibition by exogenous ABA. ABA content of mature wild-type seeds is about 10-fold the level found in mutant seeds. Nevertheless, it is argued that the differences in dormancy between the seeds of both genotypes are not a result of actual ABA levels in the mature seeds or fruits but a result of differences in ABA levels during seed development. It is hypothesized that the high levels of ABA that occur during seed development in wild-type seeds induce an inhibition of cell elongation of the radicle that can still be observed after long periods of dry storage.     

Changes in Abscisic Acid and Indoleacetic Acid before and after Anthesis Relative to Changes in Abscission Rates of Cotton Fruiting Forms

Cotton (Gossypium hirsutum L.) fruiting forms exhibit pronounced changes, with age, in their probability of abscission. Large floral buds rarely abscise, but after anthesis the young fruits (bolls) have a high probability of abscising. Abscission rate reaches a peak about 5 to 6 days after anthesis and then gradually decreases. An experiment was conducted to try to determine the reason for the rapid and pronounced increase in probability of abscission just after anthesis. Cotton was grown in the field and fruiting forms of various ages from 9 days before to 9 days after anthesis were all harvested the same day and subsequently analyzed for ABA and IAA. The concentration of ABA decreased slightly at anthesis and increased gradually thereafter. In contrast, the concentration of IAA was high before anthesis and then decreased at anthesis to about one-fifth the previous concentration. IAA remained low for at least 4 days after anthesis and then increased rapidly between 7 and 9 days after anthesis. The high concentration of IAA in floral buds before anthesis is probably a major factor in their resistance to abscission. Likewise, the low concentration of IAA at anthesis and for about 4 days thereafter may promote fruit abscission during the young boll stage.     

荔枝胚败育过程中内源激素与蛋白质含量的变化

连续3年(1999-2001年)对典型的荔枝焦核品种桂味、糯米糍和大核品种黑叶、怀枝花后10-40d的幼胚和胚乳内源激素、多酚含量及蛋白质动态变化进行研究。结果表明,焦核品种幼胚及胚乳中的IAA、GAs和ABA含量低于大核品种;多酚类物质含量在胚中低于大核品种,胚乳中则高于大核品种;胚和胚乳中的蛋白质含量均低于大核品种。蛋白质电泳结果显示,22．5、28．5和45kD这3类蛋白质在怀枝和黑叶的胚蛋白质代谢过程中表现出较高的稳定性,桂味和糯米糍胚蛋白质中的28．5kD蛋白质也有相似的特性。     

药用植物黄精种子休眠特性研究

从黄精(Polygonatum sibiricum Red.)种子的形态、解剖结构、果实及种子部分抑制物质的生物测定和种子成熟过程中内源激素ABA含量的变化等方面研究种子的休眠特性。结果表明:黄精种子休眠属于综合休眠,首先黄精种子秋季采收后其种胚存在生理后熟,是导致黄精种子深休眠的主要原因;其次黄精种子的胚乳细胞小、细胞质浓厚、排列致密,胞间隙小,影响物质的共质体运输;果实及种子中含有不同程度的发芽抑制物质;种子成熟时ABA含量升高是导致种子休眠的又一原因。     

Involvement of Endogenous Abscisic Acid in Onset and Release of Helianthus annuus Embryo Dormancy

Mature seeds of Helianthus annuus L. exhibit dormancy that is eliminated during storage in dry conditions. In vitro culture of immature embryos isolated at different times after anthesis showed that the youngest embryos are able to germinate, but within the third week after pollination, dormancy progressively affected most of the embryos. A radioimmunoassay showed that the endogenous abscisic acid (ABA) level, which increased sharply in the first half of the development period, fell at precisely the moment when embryo dormancy became established. An application of fluridone, before the increase of ABA level, prevented both ABA synthesis and development of embryo dormancy. Applied later, after the rise of the ABA level, fluridone could not prevent embryo dormancy development. Dormancy thus appears to be dependent on ABA synthesis but not concomitant with its accumulation; it must therefore be induced by ABA during maturation. Furthermore, a preincubation in water allowed dormant embryos to germinate. This acquisition of germinability could not be directly related to a leaching of free ABA. Possible effects of this treatment are discussed.     

Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability

Satsuma [Citrus unshiu (Mak) Marc.] and Clementine [Citrus reticulata (Hort.) Ex. Tanaka, cv. Oroval] are two related species of seedless mandarins which differ in their tendency to set parthenocarpic fruits. Satsuma fruits naturally set parthenocarpically whereas Clementine mandarins show very low ability to set fruit in the absence of cross-pollination. The endogenous levels of gibberellins (GAs) and free and conjugated indole-acetic acid (IAA) and abscisic acid (ABA) throughout early stages of fruit development were investigated in seedless cultivars of both species. Analyses performed by full-scan combined gas chromatography-mass spectrometry (GC-MS) of extracts from ovaries at anthesis demonstrated the presence of GA₁₉, GA₂₀, GA₂₉, GA₁, GA₈, GA₃ and iso-GA₃ in Satsuma mandarin, whereas only GA₂₉, GA₃ and trace levels of GA₈ were detected in Clementine. At this developmental stage GA-like substances, as estimated by bioassay, reached their highest levels in Satsuma, while Clementine mandarins contained relatively lower levels. In both species the highest levels of free IAA were found at petal-fall stage at which time free ABA levels also peaked. Developing fruits of Clementine had higher amounts of both free IAA and ABA. In Satsuma, levels of conjugated IAA remained low throughout reproductive development whereas in Clementine they increased as the free form declined. In contrast, conjugated ABA was at low levels in Clementine but reached higher concentrations in Satsuma. These results suggest that in these mandarins the potential for setting parthenocarpic fruits is mainly influenced by the hormonal status of the fruit during the later stages of cell division and early stages of cell enlargement. Thus, the condition of low ability to set parthenocarpic fruits appears to be associated with lower levels of active GAs, lower capability to catabolize ABA to conjugated ABA and higher ability to conjugate IAA during this period.     

‘兰箭3号’箭筈豌豆荚果发育动态及腹缝线结构研究

箭筈豌豆(Vicia sativa)是高海拔地区重要的一年生豆科牧草,但荚果成熟时的开裂现象会造成种子的严重损失。该研究以栽培品种‘兰箭3号’为对象,对其荚果在发育过程中的形态特征、水分含量、腹缝线表面结构及腹缝线横截面解剖结构的动态变化进行观察分析,以探讨箭筈豌豆荚果的裂荚机理,为生产中确定种子收获的适宜时间提供理论依据。结果显示:(1)‘兰箭3号’约在盛花后25~30d荚果变为浅棕色,此时荚果已完成生理成熟,且荚果的大小和干重均达到最大值,含水量降到最小值;盛花后25d荚果腹缝线出现裂缝,盛花后35d腹缝线完全裂开。(2)‘兰箭3号’于盛花后20d腹缝线处离层细胞开始解体;盛花后25d,内、中、外果皮的薄壁细胞均开始失水皱缩,其中内果皮的薄壁细胞部分已开始破裂,离层细胞及其下面的薄壁细胞完全解体,外部果瓣缘细胞内侧细胞壁破裂,但外侧异常加厚的细胞壁仍然保持完整并连接两个果瓣,使荚果不开裂;盛花后30~35d,内、中、外果皮的薄壁细胞完全失水,细胞壁皱缩在一起,同时外部果瓣缘细胞外侧细胞壁断裂成两部分,荚果的两个果瓣裂开。研究表明,盛花后25~30d荚果失去绿色变为浅棕色时是‘兰箭3号’的适宜收获时间,且离层和细胞失水产生的机械拉力是导致箭筈豌豆荚果开裂的主要原因,推测外部果瓣缘细胞外侧增厚融合的细胞壁很可能是‘兰箭3号’抵抗裂荚的关键结构。     

Abscisic Acid Levels in Soybean Reproductive Structures during Development

Abscisic acid (ABA) concentrations and growth rates of developing soybean (Glycine max [L.] Merr. cv. Wye) seeds and pod walls were determined from anthesis to maturation using high pressure liquid chromatographic techniques. Developing soybean seeds contain up to 12,200 ng/g fresh weight of ABA compared to 330 ng/g fresh weight for pod walls. In the developing seeds ABA levels correlated with growth rates, being the highest during the most active growth period of seed enlargement, and then decreasing to less than 10 ng/g fresh weight at maturity. Higher levels of ABA were found to occur in the cotyledons and seed coats than the root-shoot axes at 21 days postanthesis. The time required for excised root-shoot axes to initiate growth in liquid culture decreased as seed development progressed and ABA levels of the seeds declined.     

Diversities in morphological characteristics and seed germination behavior in fruits ofSalsola komarovii Iljin

Two different types of dispersal units (called fruits in this study) were observed inSalsola komarovii Iljin. One is a fruit which has dark brown lignified tepals with long wings and a green seed and falls easily from the mother plant (long-winged type). Another has light brown lignified tepals with short wings and a yellow seed and attaches tightly to the mother plant (short-winged type). This difference of fruit type appeared independently from maturity of fruit. Seeds in the short-winged fruits were in dormancy for a longer period of time than those in the long-winged fruits. The germination rate was significantly higher in the seeds of long-winged fruits. The dormancy in seeds of the long-winged fruits was effectively terminated by reducing the temperature but the effect of chilling was very weak in seeds of the short-winged fruits. It was concluded from these observations that there exists a dimorphism in the fruits of, or a heterocarpy in,S. komarovii. The plants grown under water stress produced mostly short-winged fruits and those grown under well-watered conditions bore fruits of both types. Exogenously applied abscisic acid (ABA) tended to produce the short-winged fruits, suggesting that the heterocarpy was, at least partly, regulated by ABA.     

Pod photosynthesis and seed dark CO2 fixation support oil synthesis in developingBrassica seeds

Rate of photosynthesis and activities of photosynthetic carbon reduction cycle enzymes were determined in pods (siliqua), whereas rate of dark CO₂ fixation, oil content and activities of enzymes involved in dark CO₂ metabolism were measured in seeds ofBrassica campestris L. cv. Toria at different stages of pod/seed development. The period between 14 and 35 days after anthesis corresponded to active phase of seed development during which period, seed dry weight and oil content increased sharply. Rate of pod photosynthesis and activities of photosynthetic carbon reduction cycle enzymes were maximum in younger pods but sufficiently high levels were retained up to 40 days after anthesis. The rate of dark¹⁴CO₂ fixation in seeds increased up to 21 days after anthesis and declined thereafter but maintaining sufficiently high rates till 35 days after anthesis. Similarly various enzymes viz., phosphoenolpyruvate carboxylase, NAD⁺-malate dehydrogenase and NADP⁺-malic enzyme, involved in dark CO₂ metabolism retained sufficient activities during the above period. These enzyme activities were more than adequate to maintain the desired supply of malate which mainly arises from dark CO₂ fixation in seeds and further translocated to leucoplasts for onward synthesis of fatty acids. Enzyme localization experiments revealed phosphoenolpyruvate carboxylase and enzymes of sucrose metabolism to be present only in cytosol, whereas enzymes of glycolysis were present both in cytosolic and leucoplastic fractions. These results indicated that oil synthesis in developingBrassica seeds is supported by pod photosynthesis and dark CO₂ fixation in seeds as the former serves as the source of sucrose and the latter as a source of malate