Effect of lanthanum on aged seed germination of rice

Attempts were made to promote germination of natural aged rice seeds by treating them with lanthanum nitrate. In tests to measure the germination rate, germination index, and vigor index of natural aged rice seeds were found to be significantly increased by lanthanum. It is treating aged rice seed with lanthanum nitrate that enhanced the respiratory rate and activities of superoxide dismutase, catalase, and peroxidase, and decreased superoxide and malondidehyde contents, and therefore reduced plasma membrane permeability. It suggests that lanthanum may be used to pretreat seed before sowing.     

氧化铈纳米颗粒种子引发对盐胁迫下辣椒种子萌发及幼苗生长的影响

氧化铈纳米颗粒(CeO₂NP_S),因具有较强的自由基清除能力和抗氧化酶特性,已被证明可提高植物的耐盐性,但其对辣椒种子引发作用和机制尚不明确。为揭示CeO₂NP_S种子引发处理辣椒对盐胁迫下的萌发及幼苗生长的影响,以辣椒品种(Capsicum annuum)茂蔬360为试验材料,设置了7个CeO₂NP_S浓度(0、0.05、0.1、0.2、0.3、0.4、0.5 mmol·L^-1),以未引发处理组为对照,研究不同浓度CeO₂NP_S种子引发处理后对盐胁迫下辣椒种子萌发、幼苗生物量和生理生化指标的影响。结果表明:(1)0.5 mmol·L^-1 CeO₂NP_S种子引发处理后的种子,其可溶性蛋白质、脯氨酸含量和过氧化氢酶(CAT)活性、抗坏血酸(AsA)含量和AsA/DHA比值显著提高,超氧阴离子(O₂^-)含量显著降低; 盐胁迫下,该处理种子的发芽率、发芽势、发芽指数、活力指数最大。(2)0.4 mmol·L^-1 CeO₂NP_S种子引发处理的幼苗在盐胁迫下的鲜重、干重和根长最大,幼苗的可溶性蛋白质、AsA含量和AsA/DHA比值均显著提高。综上认为,CeO₂NP_S引发处理不仅可通过降低种子水势、促进贮藏物质代谢和提高抗氧化能力提高种子在盐胁迫下的发芽率,还可在苗期通过增强蛋白合成和抗坏血酸-谷胱甘肽循环(AsA-GSH)促进盐胁迫下幼苗的生长。     

Seed germination in Chenopodium album L.: further evidence for the dependence of the effects of growth regulators on nitrate availability

Abstract Chenopodium album L. plants, grown under controlled environmental conditions on different levels of soil nitrate, produced seeds with proportionately different NO^?₃ contents. Regardless of the endogenous NO^?₃ content, few seeds germinated in water or upon treatment with KNO₃. Ethylene promoted germination, and the extent of germination was positively correlated with the endogenous seed NO^?₃ content. Combined application of ethylene and KNO₃ in the dark had a synergistic effect on NO^?₃ -deficient seed. The synergism between ethylene and KNO₃ was attributable to the NO^?₃ moiety of the nitrate salt. Ethylene and light showed moderate synergism in seeds with low or high endogenous nitrate. Addition of nitrate, however, masked the interaction between ethylene and light. Gibberellic acid₄₊₇ (GA₄₊₇) or red light, each alone or combined with KNO₃, had little effect on germination. When applied together in the dark, ethylene and GA₄₊₇ synergistically enhanced the germination of NO^?₃-deficient seed. The combined effects of the two hormones on this seed were further enhanced by the addition of KNO₃. There was no synergism between ethylene and GA₄₊₇ in NO^?₃-rich seed. These interactions among GA₄₊₇, ethylene and KNO₃ were not affected by light. The results confirm and further elaborate our earlier finding that the sensitivity of C. album seeds to ethylene may depend on nitrate availability.     

Exogenous nitric oxide improves seed germination in wheat against mitochondrial oxidative damage induced by high salinity

Effects of exogenous nitric oxide (NO) on starch degradation, oxidation in mitochondria and K⁺/Na⁺ accumulation during seed germination of wheat were investigated under a high salinity level. Seeds of winter wheat (Triticum aestivum L., cv. Huaimai 17) were pre-soaked with 0 mM or 0.1 mM of sodium nitroprusside (SNP, as nitric oxide donor) for 20 h just before germination under 300 mM NaCl. At 300 mM NaCl, exogenous NO increased germination rate and weights of coleoptile and radicle, but decreased seed weight. Exogenous NO also enhanced seed respiration rate and ATP synthesis. In addition, seed starch content decreased while soluble sugar content increased by exogenous NO pre-treatment, which was in accordance with the improved amylase activities in the germinating seeds. Exogenous NO increased the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6); whereas decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), and superoxide anions (O₂^??) release rate in the mitochondria. Exogenous NO also decreased Na⁺ concentration while increased K⁺ concentration in the seeds thereby maintained a balance between K⁺ and Na⁺ during germination under salt stress. It is concluded that exogenous NO treatment on wheat seeds may be a good option to improve seed germination and crop establishment under saline conditions.     

外源5-氨基乙酰丙酸对盐胁迫下菘蓝种子萌发及幼苗抗氧化酶活性的影响

采用砂培方式,研究了外源5-氨基乙酰丙酸(ALA)对盐胁迫下菘蓝种子的萌发、幼苗叶片的可溶性糖含量、丙二醛(MDA)含量及其抗氧化酶活性的影响,探讨ALA缓解菘蓝受盐胁迫伤害的响应机制。结果显示:(1)菘蓝种子萌发及幼苗生长在100 mmol·L^-1 NaCl胁迫下受到明显的抑制,种子发芽率、发芽势、发芽指数、活力指数与自然含水量均显著降低,丙二醛含量、可溶性糖含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)活性显著升高。(2)盐胁迫下适宜浓度的ALA处理显著提高了种子萌发率、自然含水量及SOD、POD和CAT活性,降低了可溶性糖和丙二醛的含量,并以16.7 mg·L^-1 ALA处理盐胁迫下菘蓝种子的发芽率、发芽势最大,其幼苗的SOD、POD、CAT活性最强。研究表明,盐胁迫显著抑制菘蓝种子的萌发及幼苗生长,适宜浓度的ALA能够有效缓解盐胁迫对菘蓝种子萌发及幼苗生长的伤害,提高植株的抗盐性,并以16.7 mg·L^-1 ALA处理效果最佳。     

NaCl和Na2CO3胁迫对栓皮栎种子萌发及幼苗生长的影响

为了阐明栓皮栎种子萌发期对盐碱胁迫的耐受性,研究了不同浓度(0、50、100、200和400 mmol/L)NaCl和Na2CO3胁迫对其种子萌发、生长、保护酶活性和有机渗透调节物质等的影响,结果表明:(1)盐碱胁迫对栓皮栎种子的萌发率和发芽指数均没有显著影响;随着Na+浓度的升高,NaCl和Na2CO3处理下的胚根长度、胚根生长速率、胚根鲜重均受到抑制,呈现下降趋势;活力指数和耐盐指数在NaCl胁迫下表现为较低浓度(50 mmol/L)促进,较高浓度(100,200,400 mmol/L)抑制,而在Na2CO3处理下则不断下降;相对盐害率在两种处理下均表现波动趋势。(2)通过建立活力指数、胚根长度等与Na+浓度的回归方程,发现在NaCl胁迫下栓皮栎种子活力指数、胚根鲜重、胚根长度和胚根生长速率的临界值分别为300.0、300.0、333.6、369.6 mmol/L。(3)在NaCl和Na2CO3胁迫下,随Na+浓度的增加,丙二醛含量增幅显著;NaCl处理下的SOD(superoxide dismutase)活性呈现先升高后降低的趋势,而Na2CO3处理下则均低于对照;POD(peroxidase)活性变化不显著;CAT(catalase)活性均表现为先降低后升高;脯氨酸、可溶性蛋白和可溶性糖含量均随着Na+浓度的升高而呈现不同程度上升趋势。(4)等Na+浓度时,NaCl处理下的各项生长指标均高于Na2CO3处理,丙二醛、保护酶活性及渗透调节物质含量均低于Na2CO3处理,说明Na2CO3对栓皮栎种子的影响比NaCl更为显著。     

外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。     

Dose-Response Analysis of Factors Involved in Germination and Secondary Dormancy of Seeds of Sisymbrium officinale: II. Nitrate

The role of nitrate as a promoter of germination of Sisymbrium officinale seeds was examined in optimal light conditions. It was shown that the requirement for nitrate was absolute. This was true for all seed lots used. The probit of germination in water was log-linearly related to the level of endogenous nitrate. Preincubation at 15°C resulted in an immediate decrease in germination, whereas in 25 millimolar KNO₃ the decrease was delayed. The decline of germination in water was strongly correlated with the rate at which nitrate leached from the seeds. The germination response to a range of KNO₃ concentrations was followed during preincubation at 24-hour intervals. During the entire 264-hour preincubation period increasingly higher nitrate concentrations were required to maintain a response. This resulted in a right-hand shift of the dose-response curve parallel to the x axis. After 120 hours the high maximum germination level started to decline. The dose-response curves could be simulated by an equation from the receptor-occupancy theory. It is proposed that induction of secondary dormancy is a result of a decrease of the number of nitrate receptors. After 24 and 48 hours of preincubation, the nitrate-response curves were biphasic. The biphasic character could be related to the level of endogenous nitrate and to a differential requirement for nitrate of two fractions of the seed population. Similarities with the behavior of fluence-response curves after prolonged dark incubation led to the hypothesis that phytochrome and nitrate share the same site of action.     

Alleviation of cadmium toxicity by cerium in rice seedlings is related to improved photosynthesis,elevated antioxidant enzymes and decreased oxidative stress

Cadmium contamination is a critical constraint to plant production in agricultural soils in some regions. Cerium is one of the rare earth elements, it plays a positive role in plant growth with a appropriate content. The present study was conducted to examine the role of cerium nutrition in the amelioration of effects on cadmium toxicity in rice (Oryza sativa L.) seedlings by a hydroponic experiment. Measurements included growth condition, photosynthesis related parameters, chloroplast ultra-structure and antioxidant enzymes content. Our results showed that the growth of rice seedlings was markedly inhibited by cadmium (100 μM), and the inhibition was significantly alleviated by cerium (10 μM). Fresh weight, single seedling height and chlorophyll content of rice plants in cerium treated groups were increased by 24.4, 18.2 and 32.05 % compared to those of plants cultivated in only cadmium-present condition. Additionally, in cadmium treated plants, the addition of cerium significantly increased the value of the maximum quantum yield of primary photochemistry (F _v /F _m ), indicator of PSII ‘structure and functioning’ (SFI _ABS ) and the performance index on absorption basis (PI _ABS ), elevated the activity of whole chain electron transport activity, enhanced photophosphorylation and its coupling factor Ca²⁺-ATPase activities. The result showed that the chloroplasts and thylakoid membrane of the rice seedlings leaves grown in cerium treatment developed better than that in cerium-absent group under cadmium toxicity. Moreover, addition with 10 μM cerium mitigated cadmium stress by inducing leaf enzyme activities for antioxidation like superoxide dismutase, peroxidase and catalase, dramatically depressed superoxide (O ₂ ^·? ), hydrogen peroxide and malondialdehyde accumulation. Results indicated that alleviation of cadmium toxicity by cerium application is partly related to improved light-use-efficiency, increased antioxidant enzymes, decreased oxidative stress in rice seedlings.     

盐磷胁迫对木麻黄和台湾相思种子萌发及幼苗生长的影响

恶劣环境下,人工海防林因面临养分胁迫而经营困难。为探讨盐、磷胁迫对主要海防林树种木麻黄和台湾相思种子萌发及生长的影响,该研究分别用不同浓度的NaCl(盐)和KH₂PO₄(磷)溶液处理种子和浇灌幼苗,测定种子萌发和幼苗生长指标。结果表明：(1)高盐胁迫显著抑制种子萌发,对幼苗生长有一定影响,但两种植物影响程度不同;台湾相思种子萌发耐盐性高于木麻黄,前者相对盐害率最大值为23.03%,后者为89.15%;随着盐浓度增加,木麻黄和台湾相思种子的发芽率、发芽势、发芽指数和活力指数均降低,对应最大值分别为38.70%、34.67%、18.70、0.055和76.67%、62.22%、48.46、6.11。(2)两种植物的株高和根长随盐浓度增加而降低,木麻黄和台湾相思株高分别为12.29～6.01 mm和48.27～17.33 mm,根长分别为8.57～1.45 mm和33.41～5.88 mm;台湾相思根、茎、叶生物量及根冠比均随盐浓度的增加逐渐减小,木麻黄各处理差异较小。(3)台湾相思的种子和幼苗较木麻黄更耐低磷环境,二者最适磷浓度存在差异;木麻黄种...     

盐氮处理下盐地碱蓬种子成熟过程中的离子积累和种子萌发特性

研究了盐氮处理条件下盐地碱蓬种子成熟过程中的离子积累以及种子萌发特性,以理解盐地碱蓬在种子发育及萌发过程中对高盐低氮生境的适应性。结果表明,种子成熟过程中,不同浓度盐氮处理下(0.5和5 mmol/L NO₃^--N;1和500 mmol/L NaCl),与果皮和果枝相比, 胚中Na⁺、K⁺、Cl^- 和NO₃^-离子含量几乎没有变化。所有盐氮处理下Na⁺ 和Cl^-都是果皮和果枝中高于胚中,尤其是在高盐处理下。高盐处理下,K⁺ 和NO₃^-含量呈现相反的趋势。高氮时无论高盐还是低盐,果皮中NO₃^-离子含量高于胚中,而果枝中NO₃^-离子含量低于胚中。而低氮时果皮及果枝中NO₃^-离子含量均显著低于胚中。与高氮环境下收获的种子相比,低氮环境下收获的种子萌发率,萌发指数,活力指数都要明显高。上述结果说明,盐地碱蓬种子成熟过程中存在完善的离子调控机制,保护胚免受Na⁺ 和Cl^-等有害离子的伤害并且促进K⁺ 和NO₃^-等营养离子的积累。低NO₃^--N下收获的种子对外界的NO₃^-含量比较敏感,施以较高浓度的NO₃^-能够促进种子萌发,提高萌发指数和活力指数,可能与盐地碱蓬长期适应高盐低氮生境有关。     

An efficient method for organic acetylation and use of dl-phosphinothricin as a negative selection agent in argE transgenic rice

We present an efficient method for the production of N-acetyl-l-phosphinothricin (N-AcPt) from commercial dl-phosphinothricin (DL-PPT) by organic acetylation for use as a negative selection agent (NSA) that induces cell death in argE transgenic rice. DL-PPT was efficiently converted into N-AcPt with tetrahydrofuran (THF) and acetic anhydride (Ac₂O). Chemical changes were confirmed using NMR and ATR-FTIR analyses. DL-PPT was toxic but N-AcPt did not show cytotoxic effects on leaf discs or seed germination of wild-type rice. Conversely, in argE–hpt transgenic rice, non-toxic N-AcPt showed the negative selection (NS) effect by inducing cell destruction in leaf discs and restricting seed germination. For inducing NS, ?0.1 mg ml⁻¹ and ?0.5 mg ml⁻¹ of N-AcPt were effective in leaf and seed assays, respectively. Further, the NS effect occurred faster in the leaf assay compared with the seed germination assay, again indicating the leaf assay was a more sensitive indicator of N-AcPt as an NSA to argE transgenic rice than the seed germination assay. This negative selection approach could be useful for the development of selectable marker free transgenic plants in the economically important monocot species and its commercialization for multiple gene transformation.     

Seed Germination in Chenopodium album L: Relationships between Nitrate and the Effects of Plant Hormones

Effects of ethylene, gibberellins, and kinetin on the germination of two lots of Chenopodium album L. seeds, collected from the field in 1982 and 1983, were studied in relation to the availability of nitrate. The experiments were conducted in darkness and at temperatures ranging from 12 to 32°C. Ethylene induced over 75% germination in the 1983 seed but had little effect on the 1982 seed. Nitrate was only slightly promotive in either of the two seed lots. A combination of ethylene and nitrate, however, acted synergistically on 1982 seed, resulting in as much germination as that induced in 1983 seed by ethylene alone. In 1983 seed, a combination of ethylene and nitrate was only marginally more effective than ethylene. A similar relationship was observed in the effects of gibberellic acid₄₊₇ (GA₄₊₇) and nitrate on seeds from the two lots. The 1982 seed, which responded synergistically to combinations of nitrate with ethylene or GA₄₊₇ was found to contain an extremely low endogenous level of nitrate as compared to 1983 seed. Thus, high levels of either endogenous or applied nitrate appeared to enhance the germination response to ethylene or GA₄₊₇.

Kinetin had no effect on 1982 seed and only a small promotive effect on 1983 seed. There was no synergism between kinetin and nitrate in either of the seed lots.

     

Ce^3+和La^3+对人工老化沙葱种子活力及生理特性的影响

以未老化和人工老化后的沙葱(Allium mongolicum Regel.)种子为材料,采用氯化铈(Ce3+)和氯化镧(La3+)浸种,测定种子萌发和生理指标,探讨Ce3+和La3+浸种对种子萌发、老化种子活力和生理特性的影响。结果显示:(1)在老化0~5 h时,Ce3+和La3+处理可显著促进沙葱种子萌发,提高种子活力;在老化5 h后,Ce3+和La3+处理对种子萌发无明显促进作用。(2)在老化0~15 h时,Ce3+和La3+处理的沙葱种子中抗氧化酶活性和抗坏血酸(AsA)含量提高,其超氧阴离子自由基(O2-·)产生速率、过氧化氢(H2O2)含量和丙二醛(MDA)含量显著降低;在老化15 h后,Ce3+和La3+处理的种子抗氧化酶活性提高、AsA含量降低,O2-·产生速率和MDA含量提高。(3)在老化5 h时,沙葱种子呼吸速率发生跃变达到最大,Ce3+和La3+处理显著降低了种子呼吸速率。(4)Ce3+和La3+处理在老化0~5 h时提高了沙葱种子超弱发光(UWL)强度,但在老化5 h后沙葱种子的UWL强度降低。研究认为,在沙葱种子人工老化初期,Ce3+和La3+浸种处理可以诱导增强种子抗氧化酶活性和提高AsA含量,有效清除因老化产生积累的过量活性氧(ROS),减轻过氧化伤害,提高种子活力;种子老化中后期,其内部ROS产生与清除系统发生紊乱,加剧了ROS对种子结构的损伤,Ce3+和La3+浸种处理的缓解效应丧失。     

镧提高水稻种子活力的生理生化基础研究

用５～２５ｍｇ／Ｌ浓度的Ｌａ（ＮＯ３）３溶液处理萌发期间的水稻种子,表明能加快种子的萌发,提高种子活力。其中以２０ｍｇ／Ｌ浓度处理效果最好,其次为１５ｍｇ／Ｌ浓度的处理。Ｌａ促进种子萌发的原因是由于萌发种子的呼吸速率加快,淀粉酶、蛋白酶和脂肪酶等水解酶的活性明显增加。植物内源激素ＩＡＡ、ＧＡｓ,ＣＴＫ含量明显增加,其中以ＧＡｓ的增加最为显著,ＡＢＡ含量变化不其明显,当用３０～３５ｍｇ／Ｌ的Ｌａ（Ｎ     

Relative toxicity of arsenite and arsenate on germination and early seedling growth of rice (Oryza sativa L.)

Elevated soil arsenic levels resulting from long-term use of arsenic contaminated ground for irrigation in Bangladesh may inhibit seed germination and seedling establishment of rice, the country's main food crop. A germination study on rice seeds and a short-term toxicity experiment with different concentrations of arsenite and arsenate on rice seedlings were conducted. Percent germination over control decreased significantly with increasing concentrations of arsenite and arsenate. Arsenite was found to be more toxic than arsenate for rice seed germination. There were varietal differences among the test varieties in response to arsenite and arsenate exposure. The performance of the dry season variety Purbachi was the best among the varieties. Germination of Purbachi was not inhibited at all up to 4 mg l^–1 arsenite and 8 mg l^–1 arsenate treatment. Root tolerance index (RTI) and relative shoot height (RSH) for rice seedlings decreased with increasing concentrations of arsenite and arsenate. Reduction of RTI caused by arsenate was higher than that of arsenite. In general, dry season varieties have more tolerance to arsenite or arsenate than the wet season varieties.     

Dual Effect of Light on the Gibberellin- and Nitrate-Stimulated Seed Germination of Sisymbrium officinale and Arabidopsis thaliana

Red light (R) has a dual effect on the seed germination of the two related species Arabidopsis thaliana and Sisymbrium officinale. The two species provide different means to separate the light-effects. In S. officinale, stimulation of germination by R depends on the stimultaneous presence of nitrate (light-effect I). The effect of both factors is completely blocked by tetcyclacis, an inhibitor of gibberellin (GA)-biosynthesis. Addition of a mixture of gibberellins A₄ and A₇ (GA₄₊₇) antagonizes the inhibition. In the absence of nitrate, R shifts germination to lower GA-requirement (light-effect II). In A. thaliana a similar second light-effect is seen on the GA-requirement of GA-deficient ga-1 mutant seeds. R stimulates germination of wild type seeds in water (light-effect I). For both species, light-effect I shows a fluence threshold value of approximately 10⁻⁵ moles per square meter, which is independent of the nitrate concentration. Increasing nitrate concentrations narrow the fluence-range required for maximal germination whereby the product of nitrate concentration and fluence value determines the germination level, indicating a multiplicative interaction between R and nitrate. Fluence-response curves for light-effect II are similar for both species. Germination occurs in the range of 10⁻⁶ to 10⁻² moles per square meter fluence. The maximal level of germination is determined by the level of dark-germination and light-effect II. Increasing GA₄₊₇ concentrations induce a shift to lower fluence values. It is shown that in the second effect the co-action of R and exogenous GA₄₊₇ is clearly additive. It is concluded that light-effect I induces a chain of events leading to GA biosynthesis. Light-effect II seems to enhance the sensitivity of the seeds to GAs.     

Effects of salinity and nitrate on production and germination of dimorphic seeds applied both through the mother plant and exogenously during germination in Suaeda salsa

Salinity and nitrogen are two important environmental factors that affect the distribution of halophytes in their natural saline habitats. Seeds of the euhalophyte Suaeda salsa L. were harvested from plants that had been treated with 1 or 500 mm NaCl combined with 0.5 or 5 mm NO₃^?‐N (nitrate) for 115 days in a glasshouse. Germination was evaluated under different concentrations of NaCl and nitrate. Plants exposed to high salinity (500 mm ) and low nitrate (0.5 mm ) tended to produce heavy seeds. Either high salinity (500 mm ) or high nitrate (5 mm ) increased the brown/black seed ratio. The concentrations of Na⁺, K⁺, and Cl^? were higher in brown than in black seeds, and NO₃^? concentrations were higher in black than in brown seeds, regardless of NaCl and nitrate treatments during plant culture. Regardless of NaCl and nitrate concentrations during germination, seeds from plants grown with 0.5 mm nitrate generally germinated more rapidly than seeds from plants grown with 5 mm nitrate, and the difference was greater for black than for brown seeds. Exogenous nitrate during germination enhanced the germination of brown seeds less than that of black seeds. Producing more brown seeds and heavy black or brown seeds appears to be an adaptation of S. suaeda to saline environments. Producing more black seeds, which tend to remain dormant, should reduce competition for nitrogen and appears to be an adaptation to nitrogen‐limited environments. In conclusion, nitrate provided exogenously or by mother plants to black seeds may act as a signal molecule that enhances the germination of black S. suaeda seeds.     

The effect of parent plant nutrition on seed size, viability and vigour and on germination of wheat and triticale at different temperatures

Seed was obtained from two adjacent trials of wheat (cv. Avalon) and triticale (cv. Lasko) harvested in 1990. The treatments consisted of factorial combinations of five levels of spring nitrogen (50, 100, 150, 200 and 250 kg N ha^-1) with fungicide treatments designed to control foliar diseases. Seed was graded by size into different fractions. Application of foliar fungicides to the parent plant increased the proportion of large seed in wheat but not in triticale. Fungicide application had no effect on seed vigour (quantified as the value of K; after controlled deterioration), final germination, median germination time (t₅₀) or rate of germination. Parent plant nutrition altered the proportions of seed in different size categories in triticale and wheat. In laboratory germination tests, final germination of wheat increased with seed size. Large (> 3.0 mm diameter) wheat seed from plots receiving 50 kg N ha“¹ had a lower final germination than large seed from plots which had received greater amounts of nitrogen, but t₅₀ and K; were similar for all nitrogen levels. In triticale, the higher the seed weight, the higher the final germination, the faster the rate and the higher the Ki. Final germination, t₅₀ and K;, were all positively correlated with the amount of nitrogen received by the parent plants. Parent plant nutrition had no effect on the response to temperature of final germination, t₅₀, or rate of germination for large or small seeds of both wheat and triticale.