The effect of seed drying and gibberellin treatment on the germination performance of developing carrot seed

In a succession of seed harvests of carrot, the highest percentage and most rapid germination was obtained from seed harvested 51 days after anthesis (DAA) when dried by conditioning at 25°C and 60% RH for one week and from seeeds harvested 65 or 79 DAA with or without conditioning treatment. Seed from these harvests had reached maximum weight when dried, had embryos of maximum length and were considered mature. The germinaton of seed from these treatments was unaffected by a mixture of the gibberellins A₄ and A₇ (GA_4/7) applied in the incubation medium. Seed harvested 37 DAA also gave maximum percentage germination when it was both conditioned and incubated in GA_4/7 solution. Seed harvested earlier than this germinated poorly. Germination times of both mature and immature seed were reduced after storage for 18 months but there was no response to GA_4/7.Abbreviations ABA abscisic acid - DAA days after anthesis - GA gibberellin     

Parsnip (Pastinaca sativa) seed production: effects of seed crop plant density, seed position on the mother plant, harvest date and method, and seed grading on embryo and seed size and seedling performance

Parsnip seeds from four years of seed production (1980–83) were used to examine the effects of position of the seed on the parent plant and several cultural factors on seed and embryo growth and seedling performance. Maximum seed dry weight was reached c. 50 days after flowering (DAF) but embryos continued to grow for a further 7–15 days. The coefficient of variation (C.V.) of seed weight fell from c. 35–40% at 40 DAF, to about 20–25% at maturity. The corresponding figures for C.V. of embryo length were 25–35% at the early harvest and 12–15% at maturity. The effects of seed position, plant density, harvest method, seed grading after harvest on seedling emergence and weight characters were small. Harvesting seeds c. 60 DAF gave, on average, 3.3 days earlier emergence, c. 3.6 days lower ‘spread’ of emergence time and c. 9% higher seedling emergence than harvesting 2 wk earlier. Late harvesting of the seed crop reduced the C.V. of seedling weight from 53 to 46%, on average, but there were variations in response from year to year. Seedling emergence and seedling weight characters were more closely related to embryo length than to seed weight characters.     

Germination response of black and yellow seed coated canola (<Emphasis Type="Italic">Brassica napus</Emphasis>) lines to chemical treatments under cold temperature conditions

Seed quality is a key critical component to produce well established and vigorous seedlings under cool soil (<10°C) conditions experienced in Western Canada. A simple, relatively quick germination assay is required to separate small differences in seed germination which can have a significant impact on seedling growth. It has long been established that phytohormones regulate seed germination: abscisic acid inhibits germination whereas gibberellins enhance germination. We investigated the effects of ABA, GA, ethylene and inhibitors of these phytohormones alone and in combination on the germination rate of a black and a yellow seed canola (Brassica napus) imbibed at 8°C. The effects of either saline solutions, osmotic solutions, fusicoccin or testa on the germination of canola seeds imbibed at 8°C were also investigated. This temperature is representative of the soil temperatures experienced in the early spring of Western Canada. The two canola seed lines, especially the yellow seed line, were very sensitive to increasing concentration of saline solutions at 8°C, but not at 23°C; however, iso-osmotic solutions that reduced water potential were more inhibitory. The seed coat (testa) including the endosperm was a major factor affecting the germination rate of the yellow seed line at 8°C, however, GA₄₊₇ overcame the inhibitory effect of the testa, whereas ABA exacerbated it. Fusicoccin was more stimulatory to germination than GA₄₊₇, however, unlike GA₄₊₇, it was unable to overcome the inhibitory effect of paclobutrazol, a GA biosynthesis inhibitor. Fluridone, an ABA biosynthesis inhibitor, was unable to overcome the inhibitory effects of a saline solution suggesting that the inhibitory effect was not due to elevated ABA levels. Ethylene, a stimulator of germination did not appear to be involved in the germination of these two lines. Controlled deterioration at 35°C, 85% RH could be either partially or completely overcome by exogenous GA₄₊₇. This study demonstrated the effect of hormones, salinity and testa on the germination of canola seeds under less than ideal environmental conditions.     

Self- and open-pollination as factors influencing seed quality in leek (Allium porrum)

The effect of self-pollination compared with open-pollination on leek seed weight, and subsequent seedling emergence and growth were observed for two years of seed production. Open-pollination gave higher mean seed weights and lower seedling losses during plant establishment than self-pollination. Depending upon the year, the individual plant and pollination method, between 2. 4 and 56.6% of the variation in seedling weight c. 4–5 wk after sowing under controlled conditions was accounted for by differences in seed weight and time of seedling emergence. In 1984 but not 1983, a greater proportion of the variation in seedling weight was accounted for by seed weight and time of seedling emergence in open than self-pollinated seeds.     

Fungicide seed treatments increase growth of perennial ryegrass

Field, laboratory and glasshouse experiments were carried out to measure effects of seed treatments with captan or thiram on growth of perennial ryegrass (Lolium perenne L.). Field-sown captan- or thiram-treated seed gave twice as many seedlings as untreated seed. Spaced plants growing from fungicide-treated seed produced almost 6 times more dry matter 16 weeks after sowing than those from untreated seed. This effect, though diminishing with time, was still apparent more than a year after sowing. Fungicides in sterile agar growth medium were phytotoxic to seedlings at concentrations of 10μg/ml and greater. Seedlings grown from treated seeds sown from 5 to 15 mm away from developing colonies of the virulent seedling pathogenFusarium oxysporum Schlecht. were more than 4 times larger than those grown from untreated seeds. Captan-treated seed sown into pots containing field soil produced more and larger seedlings than untreated seed. Methyl bromide fumigation of the same soil also increased both number and size of seedlings. Fungicidal, rather than direct chemical effects, at early stages of seedling growth, account for increased growth of plants from fungicide-treated seed.     

Endogenous ethylene and reversing methyl jasmonate inhibition of Amaranthus caudatus seed germination by benzyladenine or gibberellin

BA at 10^–5 M, GA₃ at 3×10^–4 M or GA₄₊₇ at 3×10^–5 M partially or largely reversed the inhibition of Amaranthus caudatus seed germination due to JA-Me. BA or GA₃ did not affect ethylene production and ACC oxidase activity in vivo in the presence of JA-Me before radicle protrusion. However, both increased ethylene production after 72 h of incubation, when the reversal of the JA-Me inhibition of seed germination was observed. AVG at 3×10^–4 M decreased ethylene production when it was applied simultaneously with BA and JA-Me or GA₃ and JA-Me, but it had no effect on seed germination. NBD almost completely reversed the stimulatory effect of BA, GA₃ or GA₄₊₇ on the germination of seeds in the presence of JA-Me. Exogenous ethylene reversed the inhibitory effect of NBD. The results indicate that action of endogenous ethylene is involved in the response of JA-Me inhibited seeds to BA or GA_s.     

Localization of Stem Elongation Control in Cucumis sativus L

Reciprocal grafts, and applications of gibberellin (GA) and indoleacetic acid (IAA) were used to localize the site of control for stem elongation in cucumber (Cucumis sativus L.). Dwarf and tall plants were reciprocally grafted to determine influence of stems and roots on stem elongation. At 21 days there were no significant differences in length between stems grafted to their own roots and those grafted to roots of the other type. GA₃, GA₄₊₇, and IAA were applied to seedlings with and without live apical buds. Seedlings with live apical buds responded to level of added GA, but not to added IAA. GA₄₊₇ was more effective than GA₃. Hypocotyls of tall plants responded more to both GA treatments than did those of the dwarves when both types had live apical buds. When either GA₄₊₇ or IAA was applied to seedlings with dead apical buds, elongation of the hypocotyl responded to level of the growth regulator, but there was no difference in response between the dwarf and tall plants.     

Relationship between gibberellic acid and water amount in the cotton seed

The role of endogenous GA₃ and its application to seed development in two cotton genotypes Hybrid-6 (H-6) (big seeds) and Gujarat cotton 13 (G. Cot) (small seeds) was studied. Kernel and seed coat were subjected to growth analysis in terms of dry weight, water amount, and rates of dry matter accumulation and water uptake. H-6 kernel had manifold higher dry weight and water amount than G. Cot. Seed coat of both genotypes had similar dry weight at maturity, but the maximum rates of dry matter accumulation and water uptake were distinctly higher in H-6. According to growth analysis, development of seed kernel and coat was subdivided into four phases, i.e., cell division, cell elongation, dry matter accumulation and maturation. Endogenous GA₃ level was estimated in kernel and seed coat by indirect ELISA using antibodies raised against GA₃. GA₃ amount per seed components was higher in the seed kernel of H-6 than of G. Cot, except 33 and 36 days after anthesis in kernel. H-6 seed coat had the higher amount of GA₃ during cell division phase than that of G. Cot. Close correlation between in vivo GA₃ level and water amount was recorded in both seed components. With GA₃ or GA₃ + NAA treatments in ovule culture, higher promotion in dry weight, water amount and seed size was noted in G. Cot than in H-6 suggesting that G. Cot is more deficient in endogenous GA₃. The greatest stimulation of parameters studied was obtained in ovule culture with GA₃ + NAA. When GA₃ or GA₃ + NAA was applied, initial significant difference in water amount and seed size was nullified. Data presented in this study indicated that GA₃ regulates cell expansion through the water uptake by cotton seed.     

金丝李果实、种子形态分化及外源物质对种子萌发和幼苗生长的影响

通过采集3个天然种群的金丝李(Garcinia paucinervis)果实,观察果实和种子的形态性状,分析其种群内和种群间的形态分化,观察不同种群种子萌发和幼苗生长的规律;采用四种植物生长调节剂和两种化学药剂,研究浸种对金丝李种子萌发和幼苗生长的影响。结果表明:金丝李种子长2.48~3.08 cm、宽1.49~1.67cm、百粒重392.50~438.18 g;3个种群果实和种子已产生明显的形态分化,胡润种群多数表型性状值在3个种群中最小,安宁种群的果实和种子偏圆,弄岗种群偏窄;在种群内部,果实和种子重量的分化较显著,整体形态较稳定;在萌发过程中,种子留存,不定根逐渐取代胚根成为主根;3个种群的萌发过程均缓慢,中间阶段几乎停滞,出苗极不整齐,萌发率表现为安宁种群(78.33%)弄岗种群(55%)胡润种群(48.33%),种子存在休眠;从种子萌发来看,以80 mg·L~(-1)的6-BA浸种24 h处理效果最好,萌发时滞最短、萌发率最高、平均萌发时间最短;结合幼苗生长情况来看,10~50 mg·L~(-1)的6-BA和500 mg·L~(-1)的GA_3处理均适宜,以50 mg·L~(-1)的6-BA效果最佳。低浓度的KNO_3和NH_4NO_3能提高萌发率,但未显著加快萌发进程,IAA和NAA对种子萌发和幼苗生长有抑制作用。该研究结果为金丝李的遗传多样性提供了形态学资料,为更好地保护、开发和利用这一珍贵树种提供了科学依据。     

Comparative effects of gibberellins and an N-substituted phthalimide on seed germination and extension growth of celery (Apium graveolens L.)

The N-substituted phthalimide AC 94377 (1-(3-chlorophthalimido)-cyclohexanecarboxamide) was equally effective as a mixture of the gibberellins A₄ and A₇ (GA_4/7) in breaking dormancy and stimulating germination of celery seeds when either was used in combination with ethephon or daminozide as a seed soak. Whereas seedlings emerging from GA_4/7-treated seeds became etiolated in comparison with those from untreated seeds, those from AC 94377-treated seeds showed normal development. Preharvest sprays of gibberellic acid (GA₃) increased the height of mature plants in comparison with untreated controls by about 16 per cent whereas AC 94377 was ineffective. The yield from GA₃-treated plots was about 10 per cent greater than that from AC 94377-treated plots.     

Overwintering and growth regulator treatment effects on celery (Apium graveolens L.) flowering and seed production

Celery (Apium graveolens L.) plants cv. Jason overwintered in a polythene tunnel flowered earlier and grew taller than similar plants given a 10-week cold-treatment at 5°C prior to transplanting in the same tunnel in mid-February. However, there was no significant difference in the yield of seeds obtained from both treatments, plants grown at a density of 4m^-2 yielded less seeds than those at 2m^-2, though the yield per unit area was slightly higher from the high density treatment. Treatment with 100 mgl^-1 GA₃ applied twice just prior to flowering and during anthesis increased flower stalk, flower pedicel and stamen length but delayed flower opening and seed ripening and decreased seed set and seed yield. Treatment with a mixture of 1000 mgl^-1 GA₄ and GA₇ plus 1000 mgl^-1 ethephon on three occasions during seed ripening decreased seed yield and reduced seed germination though those seeds capable of germinating were less dormant than seeds from untreated plants. The size distribution of seeds was unaffected by any treatment other than the preseeding spray with GA₃ which reduced the percentage of medium-size seeds.     

Differential effects of camptothecin and interactions with plant hormones on seed germination and seedling growth

Effects of camptothecin, a naturally occurring alkaloid, on seed germination varied from promotive to inhibitory, depending on the species used. It markedly inhibited seedling root growth but its inhibition of hypocotyl growth varied among species. Camptothecin inhibited GA₃-induced dark germination of lettuce (Lactuca sativa L.) seeds and hypocotyl elongation of seedlings. In contrast to ABA, the camptothecin inhibition of GA₃-induced germination could not be overcome by cytokinin. When seeds were germinated at 29C with a 0.5 h light treatment, little or no germination occurred in the camptothecin treatment, but addition of cytokinin overcame this inhibition.     

The effects of seed size and pericarp on seedling recruitment and biomass in Cryptocarya alba (Lauraceae) under two contrasting moisture regimes

Establishment success of plants derived from large seeds has been proposed to be greater than that of those derived from smaller ones, particularly under unfavourable conditions of moisture. Therefore, the advantages conferred by large seeds in terms of seedling performance may be modulated by abiotic conditions. The effect of seed size on Cryptocarya alba seedling performance (as determined by seedling recruitment and seedling size) was evaluated under two contrasting rainfall regimes (wet and dry year regime), simulated in the laboratory. It was also determined whether the presence of a pericarp, which had been shown to reduce germination, decreases desiccation and if this counterbalances the greater recruitment of seeds without a pericarp, especially under unfavourable conditions of moisture. Large seeds had a greater probability of recruitment and their seedlings attained a greater biomass, independently of the amount of water applied. In the simulated wet year regime, seeds with a pericarp showed a greater probability of recruitment than those lacking a pericarp. However, seedlings derived from both seed types attained a similar biomass. Under the dry year regime, seeds with and without a pericarp showed similar recruitment probabilities and their seedlings had similar biomasses. These results do not support the assumption that under favourable conditions of moisture, individual differences in seed size would not matter in term of seedling performance. A possible explanation in this case, is the presence of recalcitrant seeds in C. alba, which determines a very short time period for germination following dispersal. Therefore, any attribute that increases germination (e.g., large seeds) would be advantageous, independently of the prevailing abiotic conditions.     

Induction of chilling tolerance in wheat during germination by pre-soaking seed with nitric oxide and gibberellin

Chilling depresses seed germination and seedling establishment, and is one major constraint to grain yield formation in late sown winter wheat. Seeds of winter wheat (Triticum aestivum L.) were separately pre-soaked with sodium nitroprusside (SNP, as nitric oxide donor) and Gibberellic acid (GA₃) before germination and then germinated under low temperature. SNP and GA₃ pre-treatment increased seed germination rate, germination index, weights and lengths of coleoptile and radicle, while they decreased mean germination time and weight of seeds germinating under low temperature. Exogenous NO and GA₃ increased seed respiration rate and promoted starch degradation along with increased amylase activities. In addition, efficient antioxidant systems were activated by NO, and which effectively reduced concentrations of malondialdehyde and hydrogen peroxide (H₂O₂). Seedling growth was also enhanced by exogenous NO and GA₃ as a result of improved seed germination and maintenance of better reactive oxygen species homeostasis in seedling growing under chilling temperatures. It is indicated that exogenous NO was more effective than GA₃ in alleviating chilling stress during seed germination and seedling establishment in wheat.     

Effect of priming treatments on seed germination and seedling growth in bamboo [Dendrocalamus strictus (Roxb.) Nees]

Instances of flowering of bamboo species Dendrocalamus strictus are few and far between which are taken as opportunity by nurserymen to collect seeds for propagation. Germination of seeds is reported to be poor. Therefore, different seed priming treatments were applied to D. strictus seeds collected from Ranchi in order to obtain uniform and high germination. Under laboratory conditions, dehusking of seeds before sowing ensured cent percent germination. Seed priming with KNO₃ 1% solution resulted in 80.4% increase in germination followed by hydropriming by 16 h (73.1% increase). In field conditions, dehusked seeds gave 23.0% germination without any priming treatment. Priming treatment with KNO₃ 1% gave the highest rise in germination (39.1%) followed by hydropriming for 16 h (26.1%). Seeds with their seed coats intact could give germination of 9.5% when germinated without any treatment. A rise of 115.8% in germination was obtained by priming with KNO₃ 1% (final germination count 20.5%). The next best treatment was hydropriming for 16 h (final germination 18.5%, a rise of 94.7%). KNO₃ 1% also induced the earliest and the most rapid germination. When seedlings germinated in laboratory were transferred to soil, all seedlings from all treatments established successfully without any mortality whatsoever. Therefore, it is recommended that seeds should be primed for 8 h with 1% KNO₃ and germinated in laboratory or in farm house under normal atmospheric condition before transplanting the seedlings to soil.     

Dormancy of <Emphasis Type="Italic">Nicotiana benthamiana</Emphasis> seeds can be broken by different compounds

The influence of after-ripening, sodium nitroprusside, potassium ferricyanide, cyanide, paclobutrazol and nitrite on germination of seeds of Nicotiana benthamiana was investigated as well as the influence of plant hormones such as gibberellins and abscisic acid. Dormancy of N. benthamiana seeds was broken by all treatments except treatments with abscisic acid, paclobutrazol and gibberellic acid (GA₃). Gibberellins had an interesting effect on dormancy breakage of studied seeds which was dependent on use of particular gibberellin: GA₃ or GA₄₊₇. Unlike GA₃, GA₄₊₇ had broken seed dormancy.     

Stimulation of celery seed germination and seedling growth with combined ethephon,gibberellin and polyethylene glycol seed treatments

The upper-temperature limit for germination of cv. Celebrity celery seeds incubated in darkness in laboratory tests was slightly raised following a seed soak with a mixture of the gibberellins A₄ and A₇ + ethephon (G + E) but more so by osmotic priming with polyethylene glycol (PEG). However, the best effects were obtained with a combination of growth regulator and priming treatments. Incorporation of growth regulators into the PEG was more effective than soaking seeds in G + E solutions either before or after osmotic priming. In glasshouse tests, seedling emergence was more rapid, percentage emergence was higher and seedling weight was greater from seeds treated with PEG either alone or in combination with G + E than from untreated seeds, water-soaked seeds or seeds given G + E soaks before or after PEG treatment.     

外源GA3对紫斑牡丹幼苗叶片解剖结构与光合特性及内源激素含量的影响

以1年生紫斑牡丹幼苗为试验材料,采用不同浓度(0、100、300、500 mg/L)赤霉素(GA_3)喷施叶片处理,通过透射电镜、扫描电镜、光学显微镜观察幼苗叶片解剖结构,光合仪测定幼苗光合参数并以酶联免疫吸附法测叶片内源激素含量,探究外源GA_3对紫斑牡丹幼苗叶片解剖结构、光合特性和内源激素水平的影响。结果表明:(1)低浓度GA_3处理的紫斑牡丹叶肉细胞增大,栅栏组织外层细胞中叶绿体数量增加,高浓度GA_3处理则与之相反;GA_3处理叶片的栅栏组织/海绵组织比值(P/S)、组织结构紧密度(CTR)均下降,而其组织结构疏松度(SR)增加;GA_3处理的幼苗叶片的叶肉细胞内各叶绿体大小显著大于对照,随着GA_3处理浓度增加,紫斑牡丹叶肉细胞内叶绿体的体积趋于增大,类囊体垛叠凝聚逐渐松散,叶绿体上淀粉颗粒在300 mg/L GA_3处理中较明显;叶片气孔长度、宽度、气孔器大小、气孔开度和气孔密度随着GA_3浓度升高先升高后下降,同时叶片上表皮角质层厚度随GA_3浓度的升高而增加。(2)紫斑牡丹叶片净光合速率(P_n)、气孔导度(Cond)、蒸腾速率(T_r)、水分利用率(WUE)在100和300 mg/L GA_3处理下大都显著高于对照,且300 mg/L GA_3处理显著高于其余处理,而其在500 mg/L GA_3处理下显著低于对照。(3)紫斑牡丹叶片脱落酸(ABA)和吲哚乙酸(IAA)含量均在500 mg/L GA_3下显著高于对照,而在其余浓度处理下不同程度低于对照,叶片内源玉米素核苷(ZR)和GA_3含量均在300 mg/L GA_3处理下显著高于其余处理和对照,而其余处理相比对照均无显著变化;叶片的ZR/ABA、ZR/IAA、ZR/GA_3和(IAA+GA_3+ZR)/ABA比值都在300 mg/L GA_3处理下显著高于其他处理,叶片的IAA/ABA和ABA/GA_3比值均在500 mg/L GA_3处理下显著高于其他处理。研究发现,适宜浓度外源GA_3处理,能显著提高紫斑牡丹幼苗叶片光合速率、水分利用效率及蒸腾速率,调节植物体内源激素的含量及平衡,从而使叶片能合成较多有机物,促进幼苗生长。     

Effect of exogenous plant growth regulators on in vitro seed growth,embryo development,and haploid production in a cross between H. vulgare (L.) and H. bulbosum (L.)

Exogenous plant growth regulators are known to increase the efficiency of interspecific and intergeneric crosses. In vitro floret culture provides a defined system for assessing the importance of various plant growth regulators on the determinants of haploid production efficiency (seed set, embryos per seeds, and plants per embryos) in Hordeum vulgare × Hordeum bulbosum crosses. The individual and combined effects of three plant growth regulators (2,4-D, GA₃ and kinetin) on in vitro seed growth, embryo development and haploid production efficiency were tested in floret culture of the cross H. vulgare, cultivar Klages × H. bulbosum. All treatments, except kinetin alone, produced larger seeds and more embryos/100 seeds than the control (no plant growth regulator). 2,4-D alone was superior to GA₃ alone in haploid production efficiency (70.6 vs. 51.5) as measured by the number of plants regenerated/100 florets pollinated. Although kinetin +2,4-D+GA₃ produced the largest seeds and embryos, no advantage over 2,4-D alone was observed in haploid production efficiency. 2,4-D alone or kinetin +2,4-D are recommended for the purpose of barley haploid production in floret culture using the bulbosum method.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid     

Controls on seed production and seed germinability inEriophorum vaginatum

Controls on seed production in Eriophorum vagina tum were studied at two Low Arctic sites, Latnjajaure in Sweden and Toolik Lake in Alaska. At Latnjajaure, seed production was monitored for 3 years (1993-1995) in control plants and in plants that were experimentally warmed using ITEX open-topped chambers (OTCs). At Toolik Lake, experimental treatments included a factorial greenhouse x NP fertilizer experiment and artificial shading; data collection occurred in 1995, after eight seasons of treatment. Temperature differences between sites, years, and treatments all had significant effects on components of Eriophorum seed production. Pre-flo ration and post-floration times were decreased in warmer treatments and years. Ovule number per inflorescence was greater in warm years and at the warmer site, Toolik Lake. Although seed set was reduced in the OTCs at Latnjajaure, probably due to low pollination rates, in the larger greenhouses at Toolik Lake seed set was increased. The most consistent responses to temperature were in seed weight, where treatment effects were greatest at lower temperatures, such that, for example, at Latnjajaure the increases in seed weight in the OTCs were greatest in the coldest year. Fertilizer treatment had no significant effect on seed number or weight at Toolik Lake, and in the fertilizer + greenhouse treatment there were no inflorescences because Eriophorum had been nearly eliminated from the treated plots. In the shade treatment at Toolik Lake, inflorescences were fertilized but only a single mature seed was collected. Overall, the results indicate that seed production by E. vagina tum is strongly responsive to environmental variation and that only a small increase in mean summer temperatures would result in a much larger and more stable seed production.