Irrigation and Seed Quality Development in Rapid-cycling Brassica: Soluble Carbohydrates and Heat-stable Proteins

Changes in soluble carbohydrates and heat-stable proteins havebeen examined in relation to the acquisition of desiccationtolerance and/or potential seed longevity during seed developmentin rapid-cycling brassica [Brassica campestris (rapa)L.]. Ratesof seed development were moderated by different irrigation regimes.At the early stages, glucose, fructose and sucrose predominated.The raffinose series oligosaccharides accumulated during seedmaturation, and occurred earliest in seeds from plants irrigatedonly until 16 days after pollination. Stachyose content correlatedpositively, and monosaccharide content correlated negatively,with the ability of seeds to tolerate rapid desiccation andwith their potential longevity (the constantK_iof the seed viabilityequation). Similarly, the ratio of oligosaccharide[ratio]totalsugars provided strong positive correlations with ability totolerate desiccation and with potential longevity. Most of theheat-stable proteins selected for study accumulated comparativelylate, i.e. during maturation drying. The imposition of waterstress induced earlier accumulation of heat-stable proteins.The ability to tolerate desiccation was correlated with thecontent of selected heat-stable proteins, but potential longevityprovided stronger correlations. The content of a 58 kDa heat-stableprotein provided the strongest positive correlation with potentiallongevity. A simple multiple regression model of the relationsbetween potential longevity and both the oligosaccharide[ratio]totalsugar ratio and the 58 kDa heat-stable protein content was developedfor all three plant irrigation regimes to show the combinedeffect of certain sugars and proteins on seed quality. The modelsuggests that these sugars and proteins are equally likely tobe required for seed quality development, and that initiallythe sugars tend to accumulate at a greater rate than the proteins,but that during maturation drying the heat-stable proteins accumulateat the greater rate.Copyright 1998 Annals of Botany Company Brassica campestris (rapa) L., rapid-cycling brassica, potential longevity, seed development, desiccation tolerance, soluble sugars, oligosaccharides, dehydrins, heat-stable proteins.     

Seed Germination and Seedling Development in Cyclamen persicum

Cyclamen persicum Mill, seeds germinate in a narrow range oftemperature and germination is strongly inhibited by continuousirradiation with white light. The thermal optimum is approx.15 °C in both darkness and light. Seed germination is alsovery sensitive to oxygen deprivation and this sensitivity ismore pronounced at 20 °C than at the optimum 15 °C.Very immature seeds cannot germinate at any temperature, butgerminability increases during seed maturation Seedling development is unusual since seed reserves are usedimmediately for tuber formation. Tuberization is optimal at15–20 °C in light and in darkness. Supra-optimal temperatures(25–30 °C) or hypoxia inhibit tuber formation andlead to very elongated tubers These results allow the producers to improve the productionof homogeneous populations of cyclamen seedlings Wheat seeds, Triticum aestwum L., acetylcholinesterase, electrophoresis, germination, assay     

Protein Repair l-Isoaspartyl Methyltransferase1 Is Involved in Both Seed Longevity and Germination Vigor in Arabidopsis

The formation of abnormal amino acid residues is a major source of spontaneous age-related protein damage in cells. The protein l-isoaspartyl methyltransferase (PIMT) combats protein misfolding resulting from l-isoaspartyl formation by catalyzing the conversion of abnormal l-isoaspartyl residues to their normal l-aspartyl forms. In this way, the PIMT repair enzyme system contributes to longevity and survival in bacterial and animal kingdoms. Despite the discovery of PIMT activity in plants two decades ago, the role of this enzyme during plant stress adaptation and in seed longevity remains undefined. In this work, we have isolated Arabidopsis thaliana lines exhibiting altered expression of PIMT1, one of the two genes encoding the PIMT enzyme in Arabidopsis. PIMT1 overaccumulation reduced the accumulation of l-isoaspartyl residues in seed proteins and increased both seed longevity and germination vigor. Conversely, reduced PIMT1 accumulation was associated with an increase in the accumulation of l-isoaspartyl residues in the proteome of freshly harvested dry mature seeds, thus leading to heightened sensitivity to aging treatments and loss of seed vigor under stressful germination conditions. These data implicate PIMT1 as a major endogenous factor that limits abnormal l-isoaspartyl accumulation in seed proteins, thereby improving seed traits such as longevity and vigor. The PIMT repair pathway likely works in concert with other anti-aging pathways to actively eliminate deleterious protein products, thus enabling successful seedling establishment and strengthening plant proliferation in natural environments.     

Temperature and Seed Storage Longevity

Seed survival data for eight diverse species, namely the cerealbarley (Hordeum vulgare L.), the grain legumes chickpea (Cicerarietinum L.), cowpea [Vigna unguiculata (L.) Walp.] and soyabean [Glycine max (L.) Merr.], the timber trees elm (Ulmus carpinifoliaGleditsch.), mahogany (Swietenia humilis Zucc.), and terb (Terminaliabrassii Exell.), and the leaf vegetable lettuce (Lactuca sativaL.) were compared over a wide range of storage environments(temperatures from –13 °C to 90 °C, seed moisturecontents from 1.8 to 25% f. wt) using a viability equation developedpreviously. In accordance with that equation, the effect oftemperature on seed longevity was dependent upon the temperaturerange. The temperature coefficients of the viability equationdid not differ significantly (P > 0.05) among the eight speciesdespite their contrasting taxonomy. Thus the quantitative relationbetween seed longevity and temperature does not vary among diversespecies. The same conclusion was obtained for the coefficientsof a proposed alternative model of the relation between seedlongevity and temperature. The implications of the two temperaturemodels in the viability equation for extrapolations to low andvery low temperatures are discussed. Seed storage, seed longevity, seed moisture, temperature, viability equation, genetic resources conservation, Cicer arietinum L., Glycine max (L.) Merr., Hordeum vulgare L., Lactuca sativa L., Swietenia humilis Zucc., Terminalia brassii Exell., Ulmus carpinifolia Gleditsch., Vigna unguiculata (L.) Walp     

Arabinan Metabolism during Seed Development and Germination in Arabidopsis

Arabinans are found in the pectic network of many cell walls, where, along with galactan, they are present as side chains of Rhamnogalacturonan I. Whilst arabinans have been reported to be abundant polymers in the cell walls of seeds from a range of plant species, their proposed role as a storage reserve has not been thoroughly investigated. In the cell walls of Arabidopsis seeds, arabinose accounts for approximately 40% of the monosaccharide composition of non- cellulosic polysaccharides of embryos. Arabinose levels decline to -15% during seedling establishment, indicating that cell wall arabinans may be mobilized during germination. Immunolocalization of arabinan in embryos, seeds, and seedlings reveals that arabinans accumulate in developing and mature embryos, but disappear during germination and seedling establishment. Experiments using 14C-arabinose show that it is readily incorporated and metabolized in growing seedlings, indicating an active catabolic pathway for this sugar. We found that depleting arabinans in seeds using a fungal arabinanase causes delayed seedling growth, lending support to the hypothesis that these polymers may help fuel early seedling growth.     

成熟脱水对种子发育和萌发的作用

成熟脱水是正常性种子发育的末端事件。种子在成熟时胚的脱水耐性增加;当种子萌发时胚变得不耐脱水。当种子获得脱水耐性时,糖、蛋白质和抗氧化防御系统等保护性物质积累;当脱水耐性丧失时,这些物质被降解。成熟脱水是种子从发育过程向萌发过程转变的“开关”,它降低发育的蛋白质和mRNA的合成,终止发育事件和促进萌发事件。顽拗性种子不经历成熟脱水的发育阶段,对脱水高度敏感。     

Rapid-cycling Brassica Species: Inbreeding and Selection of B. campestris for Anther Culture Ability

A study was made to determine the feasibility of producing,by inbreeding and selection, lines of rapid-cycling Brassicacampestris with high or low potential for anther culture. Sincethe base population of rapid-cycling B. campestris is self-incompatible,inbreeding was achieved by a combination of bud-pollinationand the application of pollen to the cut surfaces of decapitatedstigmas. Three inbred generations were raised, and in each generationplants were selected for high or low potential for anther embryogenesis.The proportion of viable pollen present in anthers, as indicatedby a fluorochromatic reaction and a germination test, was alsodetermined at each stage. Lines of rapid-cycling B. campestriswith clearly defined high or low potential for anther embryogenesiswere isolated in these experiments. Within each line, however,continuous variation was always observed. Pollen viability andanther efficiency were not correlated. Although inbreeding depressioncaused a significant decrease in pollen viability over the threegenerations, there were no obvious deleterious effects on antherefficiency. In general, over the three generations of inbreeding,no segregation in plant morphological characters was observed,although many developmental abnormalities were seen in the 3rdinbred generation and there was a marked reduction in the numberof seeds set. No association between plant vigour and high orlow anther efficiency was noted. All plants regenerated fromanther embryoids of rapid cycling B. campestris were haploid.By treating anther-derived embryoids, axillary buds and wholeplants with colchicine, dihaploid plants were produced, butthese failed to set seed after self-pollination. The diploidnature of the plants was confirmed, however, when they producednormal seeds after cross-pollination with plants of the basepopulation. Brassica campestris, anther culture, inbreeding, selection     

种子发育与萌发过程中的程序性细胞死亡

禾谷类种子胚乳发育过程中的程序性细胞死亡(PCD)主要发生在种子成熟期的后期,并伴随着生物合成的停止和自然脱水;乙烯和活性氧促进胚乳发育中的PCD,而ABA起负调节作用。种子萌发过程中糊粉层降解的PCD被GA、Ca^2 和活性氧促进,被ABA和抗氧化剂抑制。种子人工老化和劣变种子萌发过程中可能存在PCD事件,其研究对延长种子的贮藏寿命和提高播种品质具有重要的意义。     

一种快速生长的甘蓝型油菜DH系的获得和鉴定

从快速生长的甘蓝型油菜的小孢子培养中共获得23个再生植株。经倍性鉴定,其中自发加倍成二倍体的有10株,单倍体13株。单倍体再用秋水仙碱处理后获得DH系,所得材料对油菜功能基因组学的研究可能有一定的价值。     

Effect of Different Seed Storage Conditions on Germination and Isozyme Activity in Some Brassica Species

Sixteen seed accessions of four Brassica species (B. cretica,B. incana, B. montana and B. oleracea) were examined following5-22 years' storage in the germplasm bank. Germinability andisozyme of seeds stored under long-term (-10 °C and 3% moisturecontent) and short-term (5% °C and 8% moisture content)storage conditions were compared. Long-term storage producedno deterioration and the ability to germinate was satisfactorilymaintained over 8-22 years. Short-term storage conditions maintainedgermination ability up to 10-12 years in all accessions of B.cretica and B. montana. However, seed multiplication might beessential every 10 years for some accessions of B. oleraceastored in this way. In the 8 to 9-year-old accessions of B.cretica, B. incana and B. montana, no significant differenceswere detected between conservation systems for germinabilityand frequency of seeds showing isozyme activity for seven enzymesystems (ACO, IDH, MDH, ME, PGI, PGM and 6-PGD). However, significantdifferences were found for the ADH enzyme system. Moreover,in the 5-22-year-old B. oleracea accessions, significant differenceswere found between storage conditions with respect to isozymeactivity for all enzyme systems studied.Copyright 1995, 1999Academic Press Brassica cretica, Brassica incana, Brassica montana, Brassica oleracea, accessions, isozymes, germination, seed storage     

壳聚糖包衣对油菜种子萌发及幼苗耐盐性影响

以不同浓度的壳聚糖对油菜种子进行包衣处理,考察其对油菜种子萌发及幼苗耐盐性的影响,并在不同盐浓度胁迫条件下对种子萌发时的发芽势、发芽率、生物量（鲜重、干重、根长、芽长）等指标进行测定,同时分析油菜幼苗叶绿素含量、可溶性蛋白及可溶性糖含量的变化。结果表明,一定浓度的壳聚糖包衣处理可提高油菜种子发芽率、发芽势、生物量、幼苗的耐盐指数、叶绿素含量、可溶性蛋白及可溶性糖的含量,其中浓度为0.25 g·L^-1壳聚糖包衣处理对油菜种子萌发的促进效果较好,而浓度为0.50 g·L^-1壳聚糖包衣处理对提高油菜幼苗耐盐性具有较好的促进作用。     

Rapid-cycling Brassica Species: Inbreeding and Selection of Brassica napus for Anther Culture Ability and an Assessment of its Potential for Microspore Culture

A study was made to determine the feasibility of producing,by inbreeding and selection, lines of rapidcycling Brassicanapus L. with high or low potential for anther culture. In contrastto previous observations of B. campestris L., a self-incompatiblespecies, the anther culture potential of the plants of successiveinbred generations of B. napus remained uniform, and antherefficiency was poor, with a maximum of 0.476 embryoids producedfor each anther plated. This negative response to selectionmay have been due to an absence of variation with respect toanther culture ability in the base population, resulting fromthe self-fertility of the species. Cytological studies of culturedanthers of B. napus indicated that in each generation therewas a poor correlation between pollen induction and embryoidproduction. In an attempt to improve the yield of haploid embryoids of B.napus, isolated microspore culture was attempted, and was foundto be at least 60 times more efficient than anther culture,with as many as 32 embryoids being produced from each anther.In experiments designed to ascertain the reasons for such differences,an inhibitory effect of the anther wall on the anther embryogenesisof B. napus was observed, and embryoid yields were improvedby centrifuging buds prior to anther extraction to simulatethe effects of the centrifugation which is a component of themicrospore preparation procedure. Brassica napus, L. anther culture, microspore culture, inbreeding, selection     

Phytochrome and Seed Germination: VI. Phytochrome and Temperature Interaction in the Control of Cucumber Seed Germination

Phytochrome control of cucumber seed germination is temperature-dependent. A prolonged exposure to radiation from broad spectrum far red sources (Pfr/P = 0.05 to 0.07) prevents germination at temperatures below 20 C. Above 20 C there is no inhibition and it appears as if there is an escape from phytochrome control. However, radiation from a monochromatic, narrow band 730 nanometer source (Pfr/P < 0.02) inhibits germination at temperatures above 20 C. This result supports the idea that, even at high temperatures, Pfr is responsible for the activation of germination. After 4 days of exposure to far red, a short red irradiation is quite effective in promoting germination if temperatures during the dark incubation periods are maintained below 20 C; red becomes effective at temperatures above 20 C. Promotion of germination will take place at a temperature of 25 C or higher without red irradiation. Again, we have an apparent escape from phytochrome control at high temperatures. However, if higher temperatures are used for only short periods, 2 to 6 hours, in combination with short red irradiation, one can demonstrate that activation of germination at high temperatures is still dependent on phytochrome. Phytochrome is probably destroyed during prolonged exposure to far red. Thus, the subsequent short red irradiation establishes levels of Pfr which may not be sufficient to promote germination at low temperatures but are probably adequate at high temperatures.     

Biochemical Changes Associated with Brassica juncea Seed Development, II: Glycosidases

Changes in α- and β-galactosidase, glucosidase, and α-mannosidase and β-xylosidase activities were analyzed in developing mustard (Brassica juncea) seed. A cubic polynomial described the seed dry weight data adequately. A close parallelism between the water content and dry matter accumulation was shown (r= 0.991). Glycosidase activities were detected in both cytoplasmic and wall fractions. The trend was similar in both of the fractions, but the activity of α-mannosidase and α-galactosidase was considerably greater in the wall-bound fraction. The water content and the activity of glycosidic enzymes showed a significant linear correlation (p < 0.001). The results suggest that glycosidases have an important role in cell wall loosening during mustard seed development. Received July 10, 1997; accepted January 28, 1998     

The Effect of Chilling and Moisture Status on the Germination, Desiccation Tolerance and Longevity ofAesculus hippocastanumL. Seed

Effects of 2 °C chilling on the threshold moisture contentsand water potentials for various physiological processes wereestimated forAesculus hippocastanumL. seed. Seed harvested atthe time of maximum seed fall exhibited a dual response to drying:partial drying from near 50% to 32–40% moisture contentprogressively increased germination percentage (at 16 °C)up to various peak values; further desiccation was detrimental,confirming that the seeds are ‘recalcitrant’. Themoisture content for optimum germination was increased by atleast 10% as the chilling period was raised from 0 to 9 weeks.A negative linear relationship was found between log₁₀mean timeto germinate and probit final germination, regardless of pre-treatment,indicating that partial desiccation and chilling are interchangeablein promoting germination of hydrated seed. For nearly fullyhydrated seeds, increasing the chilling period from 6 to 26weeks increased the viability-loss onset point for desiccationinjury from near 40% to about 48% moisture content without alteringthe drying rates of seed tissues. Extending moist chilling invarious seed lots from 0 to 26 weeks decreased subsequent longevityat 16 °C. For 26-week-chilled seeds longevity (the periodto lose one probit of germination) differed above and belowa threshold moisture content of 48%. It remained constant inthe moisture-content range 48–38%, but increased progressivelyas moisture content was raised above 48%. This threshold moisturecontent coincided with the value above which chilled seed pre-germinatedin storage. The results indicate that post-harvest desiccationand chilling alter the water relations of various physiologicalprocesses and a schematic summary is presented which relatesthe results to an axis water sorption isotherm.Copyright 1998Annals of Botany Company Aesculus hippocastanumL., horse chestnut, chilling, moisture content, water potential, desiccation tolerance, longevity, recalcitrant seed, embryo axis, maturation, germination.     

Asymbiotic Seed Germination and in vitro Seedling Rapid Development of Paphiopedilum spicerianum

In this paper, we studied the asymbiotic seed germination and seedling development of Paphiopedilum spicerianum, a wild plant with extremely small populations (PSESP) in China. By analogizing the influences of different media, seed maturity, pretreatments and lights on the seed germination, the results showed that the best germination condition is using the seeds at 270 days after pollination, pretreating with 1% NaOCl for 40 min, on the 1/4MS+10% coconut water medium under 24 hours darkness for 4 weeks. For seedling formation, 30g·L-1 Hyponex No 1 medium with 10mg·L-1 α naphthlene acetic acid, 05g·L-1 activated charcoal and 10% banana homogenate was the most effective. For seedling development, the same medium used for seedling formation with supplemented 10g·L-1 6 benzyladenine was most suitable.