Polyamines and ethylene in rice young panicles in response to soil drought during panicle differentiation

This study tested the hypothesis that polyamines (PA) and ethylene (ETH) mediate the effects of soil drought on spikelet development in rice (Oryza sativa L.). Two rice cultivars, Yong You-2640 and Yang Dao-6, with vastly different panicle sizes were grown in pots under three soil moisture treatments: well-watered (WW), moderate soil drought (MD) and severe soil drought (SD), from the onset of panicle initiation to the pollen completion stage. MD treatment significantly increased spikelet differentiation, spikelet number per panicle, fully filled grain percentage and grain yield, decreasing the percentage of degenerated spikelets, sterile spikelets and partially filled grains compared to WW treatment. In contrast, SD treatment showed opposite effects. MD also increased the contents of free spermidine (Spd), free spermine (Spm) and the ratios of free putrescine, free-Spd and free-Spm to 1-aminocylopropane-1-carboxylic acid (ACC), decreasing the ETH evolution rate and ACC content in young panicles. In contrast, SD treatment showed opposite effects. Furthermore, free-Spd and free-Spm contents increased significantly, while ETH and ACC levels, and the percentage of degenerated and sterile spikelets decreased significantly under application of Spd or an inhibitor of ETH synthesis. The results were reversed when ACC or an inhibitor of Spd and Spm synthesis was applied. These findings suggest antagonistic interactions between free-PA (Spd and Spm) and ETH in response to soil drought, mediating spikelet development in rice.     

Interactions between polyamines and ethylene during grain filling in wheat grown under water deficit conditions

This study was to test the hypothesis that polyamines (PAs) and ethylene may be involved in mediating the effect of water deficit on grain filling. Two wheat cultivars, drought-tolerant Shannong16 (SN16) and drought-sensitive Jimai22 (JM22), were used and subjected to well-watered and severe water deficit (SD) during grain filling. SD reduced the weight of superior and inferior grains, by 7.38 and 23.54 % in JM22, 13.8 and 2.2 % in SN16, respectively. Higher free-spermidine (Spd) and free-spermine (Spm) concentration and lower free-putrescine (Put) concentration, ethylene evolution rate (EER) and 1-aminocylopropane-1-carboxylic acid (ACC) concentration were found in superior grains than those in inferior ones. Opposite to the variations of Spd and Spm concentration, ACC, Put concentration and EER were significantly increased under SD. The percentage variation of PAs and ACC differed with cultivars and grain types. ACC concentration of superior and inferior grains under SD increased significantly at 21 days post-anthesis, by 90 and 164 % in JM22, 65 and 13.2 % in SN16, respectively. The equivalent value of Put concentration was 1.04 and 7.9 % in JM22, 34.4 and 10.3 % in SN16. Spd concentration of superior grains showed a higher decrease than that of inferior ones in both cultivars, while Spm exhibited an opposite trend between both grain types. These percentage variations were highly consistent with the differed responses of weight of both grain types to SD in JM22 and SN16. Grain filling rate was negatively correlated with EER and ACC concentration, while positively correlated with Spd and Spm concentration as well as the ratio of Spd or Spm to ACC. Exogenous Spd or aminoethoxyvinylglycine (an inhibitor of ethylene synthesis by inhibiting ACC synthesis) obviously reduced ACC concentration and EER and increased Spd and Spm concentration, while exogenous ethephon (an ethylene-releasing agent) or methylglyoxal-bis (an inhibitor of Spd and Spm synthesis) showed the opposite effects. The results suggested that it would be good for wheat to have the physiological traits of higher Spd and Spm, as well as a higher Spd/ACC or Spm/ACC, under SD.     

Involvement of polyamines in the post-anthesis development of inferior and superior spikelets in rice

Early-flowered superior spikelets usually exhibit a faster grain filling rate and heavier grain weight than late-flowered inferior spikelets in rice (Oryza sativa L.). But the intrinsic factors responsible for the variations between the two types of spikelets are unclear. This study investigated whether and how polyamines (PAs) are involved in regulating post-anthesis development of rice spikelets. Six rice genotypes differing in grain filling rate were field grown, and PA levels and activities of the enzymes involved in PA biosynthesis were measured in both superior and inferior spikelets. The results showed that superior spikelets exhibited higher levels of free spermidine (Spd) and free spermine (Spm) and higher activities of arginine decarboxylase (ADC, EC 4.1.1.19), S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) and Spd synthase (EC 2.5.1.16) than inferior spikelets at the early endosperm cell division and grain filling stage. The maximum concentrations of free Spd and free Spm and the maximum activities of ADC, SAMDC and Spd synthase were significantly correlated with the maximum cell division and grain filling rates, maximum cell number and grain weight. Application of Spd and Spm to panicles resulted in significantly higher rates of endosperm cell division and grain filling in inferior spikelets along with the activities of sucrose synthase (EC 2.4.1.13), ADP glucose pyrophosphorylase (EC 2.7.7.27) and soluble starch synthase (EC 2.4.1.21), suggesting that these PAs are involved in the sucrose-starch metabolic pathway. The results indicate that the poor development of inferior spikelets is attributed, at least partly, to the low PA level and its low biosynthetic activity.     

Post-anthesis development of inferior and superior spikelets in rice in relation to abscisic acid and ethylene

The purpose of this study was to test the hypothesis that the interaction between abscisic acid (ABA) and ethylene may be involved in mediating the post-anthesis development of spikelets in rice (Oryza sativa L.). Two rice genotypes were field-grown, and the changes of ABA, ethylene, and 1-aminocylopropane-1-carboxylic acid (ACC) levels in spikelets during grain filling and their relationships with endosperm-division and grain-filling rates were investigated. The results showed that earlier-flowering superior spikelets exerted dominance over later-flowering inferior spikelets in endosperm cell-division and grain-filling rates. The two genotypes behaved the same. Later-flowering spikelets had higher levels of ethylene and ACC than earlier-flowering spikelets. The ethylene evolution rate was significantly and negatively correlated with the cell division and grain filling rates. By contrast to ethylene, later-flowering spikelets contained a lower ABA content/concentration and showed a low content ratio of ABA to ACC than earlier-flowering ones. The cell-division and grain-filling rates were significantly and positively correlated with both ABA contents and the ratio of ABA to ACC. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at an early grain-filling stage significantly increased endosperm cell division rate and cell number, grain-filling rate, and grain weight of inferior spikelets. Application of ethephon (an ethylene-releasing agent) or fluridone (an inhibitor of carotenoid synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene mediate endosperm cell-division and grain-filling in rice. A higher ratio of ABA to ethylene in rice spikelets is required to maintain a faster grain-filling rate.     

The Relationship between Polyamines and Hormones in the Regulation of Wheat Grain Filling

The grain weight of wheat is strongly influenced by filling. Polyamines (PA) are involved in regulating plant growth. However, the effects of PA on wheat grain filling and its mechanism of action are unclear. The objective of the present study was to investigate the relationship between PAs and hormones in the regulation of wheat grain filling. Three PAs, spermidine (Spd), spermine (Spm), and putrescine (Put), were exogenously applied, and the grain filling characteristics and changes in endogenous PA and hormones, i.e., indole-3-acetic acid (IAA), zeatin (Z) + zeatin riboside (ZR), abscisic acid (ABA), ethylene (ETH) and gibberellin 1+4 (GAs), were quantified during wheat grain filling. Exogenous applications of Spd and Spm significantly increased the grain filling rate and weight, but exogenous Put had no significant effects on these measures. Exogenous Spd and Spm significantly increased the endogenous Spd, Spm, Z+ZR, ABA, and IAA contents and significantly decreased ETH evolution in grains. The endogenous Spd, Spm and Z+ZR contents were positively and significantly correlated with the grain filling rate and weight of wheat, and the endogenous ETH evolution was negatively and significantly correlated with the wheat grain filling rate and weight. Based upon these results, we concluded that PAs were involved in the balance of hormones that regulated the grain filling of wheat.     

Growth characteristics and endosperm structure of superior and inferior spikelets of indica rice under high-temperature stress

Heat stress severely reduces rice yield and quality; however, differences between the superior, early-flowering and inferior, later-flowering spikelets of indica rice in response to high-temperature stress during grain filling remain unclear. This study investigated the effects of high temperature (HT, 33.6/20.7 °C day/night) on growth, endosperm structure, and hormone and polyamine content of superior and inferior spikelets of heat-sensitive (SG-1) and heat-tolerant (HHZ) indica cultivars. The HT decreased fertilization rate, caused earlier grain filling, and reduced duration of grain filling, thus resulting in decreased grain mass and a poor endosperm structure. In addition, soluble sugar and sucrose content increased, and starch synthesis decreased by HT at the early stage of grain filling. The HT increased polyamine [spermidine (Spd) and spermine (Spm)] and abscisic acid (ABA) content, but reduced zeatin (Z) + zeatin riboside (ZR) and indole-3-acetic acid (IAA) content in the grains. Such effects were more apparent in the inferior than superior spikelets; however, the inferior spikelets of SG-1 were more affected than those of HHZ. At the middle grain filling stage, HT produced little difference between the two cultivars. Our results suggest that the poor development of inferior spikelets of SG-1 under the HT could be attributed, at least in part, to the changed content and ratios of free polyamines [putrescine (Put), Spd, and Spm] and phytohormones (Z+ZR, IAA, and ABA) and the conversion efficiency of sucrose into starch.     

月季切花衰老过程中多胺与乙烯的关系

月季切花瓶插过程中,内源腐胺在前2天略有增加,内源亚精胺、精胺、多胺总量则呈下降趋势,乙烯释放速率在第3天达到最高峰;多胺抑制剂甲基乙醛-双咪腙处理抑制了亚精胺、精胺的合成,增加了乙烯的释放速率;乙烯抑制剂氨氧乙酸处理推迟腐胺高峰的到来,降低了乙烯的释放速率,而且在瓶插期的前2天内源亚精胺、精胺含量较高。结果表明,具乙烯跃变型特征的月季切花衰老过程中,多胺与乙烯在其生物合成过程中相互竞争S-腺苷甲硫氨酸作为其合成的前体。     

Involvement of abscisic acid and ethylene in the responses of rice grains to water stress during filling

This study was to test the hypothesis that the interaction between abscisic acid (ABA) and ethylene may be involved in mediating the effects of water stress on grain filling. Two high lodging‐resistant rice (Oryza sativa L.) cultivars were pot‐grown. Three treatments, well‐watered, moderate water‐stressed (MD), and severe water‐stressed (SD), were imposed from 9 d post‐anthesis until maturity. Grain filling rate and grain weight were significantly increased under MD but decreased under SD. The two cultivars behaved the same. ABA concentration in the grains was very low during the grain filling stage, reaching a maximum when the grain filling rate was highest. Both the grain filling rate and ABA concentration were substantially enhanced by water stress. In contrast to ABA, concentrations of ethylene and 1‐aminocylopropane ‐1‐carboxylic acid (ACC) in the grains were very high at early grain filling stage and sharply decreased during the linear period of grain growth. MD reduced, whereas SD remarkably increased, their accumulation. The ratio of ABA to ACC was increased in MD grains but decreased in SD grains, indicating that there was a greater enhancement of ABA concentration than ethylene production in the MD treatment only. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at the early grain filling stage significantly increased grain filling rate. Spraying with ethephon (ethylene‐releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene mediate the grain filling rate, and a high ratio of ABA to ethylene enhances grain filling rate.     

水稻细胞质雄性不育系幼穗发育过程中多胺与乙烯的关系初探(英文 )

利用ＨＰＬＣ和ＧＣ分别测定了水稻细胞质雄性不育系及其保持系幼穗多胺（ 腐胺,亚精胺和精胺） 含量和乙烯释放速率,并研究了外施多胺合成抑制剂ＭＧＢＧ 和乙烯前体ＡＣＣ生成抑制剂ＡＶＧ 对两系幼穗多胺含量和乙烯释放速率以及花粉育性的影响。结果表明, 不育系幼穗乙烯释放速率显著高于其保持系幼穗, 外施ＡＶＧ 引起两系幼穗乙烯释放速率下降,并使不育系花粉育性得以部分恢复; 不育系幼穗多胺含量显著低于保持系幼穗, 外施ＭＧＢＧ 使两系幼穗Ｓｐｄ 和Ｓｐｍ 含量下降, 并使保持系花粉育性降低。外施ＡＶＧ 抑制乙烯释放,促进多胺合成;而外施ＭＧＢＧ 抑制Ｓｐｄ和Ｓｐｍ 合成, 却促进乙烯的释放; 而且,乙烯释放速率与多胺（精胺和亚精胺） 含量呈显著负相关。提示在水稻ＣＭＳ 系及其保持系幼穗发育过程中乙烯与多胺（ 精胺和亚精胺） 的生物合成竞争ＳＡＭ。     

Ethylene control of seed coat development in low and high sterile semidwarf indica rice cultivars

Although basally positioned inferior spikelets of rice panicles emerge late from the flag leaf enclosure (boot), they mature early which precludes adequate grain filling. It is assumed that extended exposure to ethylene inside the boot restricts assimilate partitioning to the endosperm in basal spikelets by affecting the functions of seed coat. In the present study, ethylene concentration inside the boot was measured in two high yielding rice cultivars differing in percentage of spikelet sterility. To manipulate the concentration/action of ethylene, silver nitrate, aminoethoxyvinyl glycine and 2-chloroethylphosphonic acid were injected into the boot. The effect of these chemicals on the concentration of photosynthetic pigments, lipid peroxidation and peroxidase activity of the seed coat and lemma and palea were measured to monitor development. Ethylene reduced development during the juvenile phase but accelerated degradation of the photosynthetic tissues of the spikelets in the senescent phase. Boot ethylene correlated positively with number of barren spikelets in the panicle and negatively with concentration of photosynthetic pigments of the seed coat of inferior spikelets. The concentration of ethylene was higher in the high sterile cultivar Mahalaxmi than that of the low sterile Mahanadi. Inhibition of ethylene action or synthesis improved grain filling. The chemicals were most effective on the inferior spikelets. It was concluded that ethylene retarded seed coat development during the prestorage phase and reduced grain filling of basal spikelets.     

Ethylene and ACC levels in developing grains are related to the poor appearance and milling quality of rice

The possible relationship between the levels of ethylene and 1-aminocylopropane-1-carboxylic acid (ACC) in the grains and the quality of rice (Oryza sativa L.) were investigated by using 12 rice cultivars. The results showed that both the ethylene evolution rate and ACC content in grains during the grain filling period correlated negatively with head rice production and positively with chalky kernels, chalky size, and chalkiness. The levels of ethylene and ACC were not significantly correlated with alkali spreading value and amylose content. Application of ethephon, an ethylene-releasing agent, or ACC to panicles at the early grain filling stage significantly reduced the rates of brown rice, milled rice, and head rice, and significantly increased the percentage of chalky kernels, chalky size, and chalkiness. Application of aminoethoxyvinylglycine, an inhibitor of ACC synthase, had the opposite effect. Chalkiness appears to be a senescence related phenomenon which is stimulated by ethylene. The results suggest that ethylene and ACC in grains play an important role in regulating rice quality, and that grain appearance and milling quality would be improved though the reduction of ethylene and ACC in grains during grain filling.     

Polyamines and ethylene in the removal of embryonal dormancy in apple seeds

Putrescine (Put), spermidine (Spd) and spermine (Spm) were found in seeds of apple ( Malus domestica Borkh. cv. Antonovka), in amounts that increased in the order given. The levels slowly decreased during 30 days of stratification. Exogenous polyamines (PAs) affected germination of isolated embryos in a way dependent on the type of polyamine, its concentration, and the state of the embryo dormancy. The effect of Put and Spd on germination was stimulatory, while that of Spm was inhibitory. Stimulation of germination was also observed when embryos were treated with arginine, ornithine and methionine. Canavanine inhibited germination, and this effect was reversed by arginine or Put. Ethephon, aminooxyacetic acid (AOA) and aminoethoxyvinylglycine (AVG) present during seed stratification had no effect on the levels of endogenous PAs. Put and Spd did not change ethylene production, neither during seed stratification nor during embryo germination, whereas Spm reduced ethylene evolution. The data suggest that Spm plays a role in the maintenance of dormancy by preventing ethylene production, while Put and Spd participate in dormancy removal, independently of ethylene.     

Abscisic acid and ethylene interact in wheat grains in response to soil drying during grain filling

Grain filling is an intensive transportation process regulated by soil drying and plant hormones. This study investigated how the interaction between abscisic acid (ABA) and ethylene is involved in mediating the effects of soil drying on grain filling in wheat (Triticum aestivum). Two wheat cultivars, cv. Yangmai 6 and cv. Yangmai 11, were field-grown, and three irrigation treatments, well-watered, moderately soil-dried (MD) and severely soil-dried (SD), were imposed from 9 d post anthesis until maturity. A higher ABA concentration and lower concentrations of ethylene and 1-aminocylopropane-1-carboxylic acid (ACC) were found in superior grains (within a spike, those grains that were filled earlier and reached a greater size) than in inferior grains (within a spike, those grains that were filled later and were smaller), and were associated with a higher filling rate in the superior grains. An increase in ABA concentration and reductions in ethylene and ACC concentrations in grains under MD conditions increased the grain-filling rate, whereas much higher ethylene, ACC and ABA concentrations under SD conditions reduced the grain-filling rate. Application of chemical regulators gave similar results. The results did not differ between the two cultivars. The grain-filling rate in wheat is mediated by the balance between ABA and ethylene in the grains, and an increase in the ratio of ABA to ethylene increases the grain-filling rate.     

Flower fertilization and fruit development prompt changes in free polyamines and ethylene in damson plum (Prunus insititia L.)

The flower opening of damson plum (Prunus insititia L.) was accompanied by an increase in the content of free-polyamines (PA) in the sepals, petals and sex organs, the ovary being most active in accumulating spermine (Spm). The fertilization process and senescence brought on a decline in ovarian Spm, but stimulated putrescine (Put) and spermidine (Spd) content in the sepals. The endocarp of this climacteric fruit produced only ethylene at the end of the S1 phase and throughout S2, in which there was a great richness in ACC and MACC. The greatest amounts of ACC and MACC were observed in the ripening mesocarp and epicarp. The contribution of the endocarp and epicarp to the total ACC in the developing fruit was very similar. During flowering and S1 and S2 phases, Spd was the most abundant PA; in contrast, during S3 and S4 Put was most abundant. The mesocarp contributed the most to the total content in PA throughout the fruit development. The control of SAM distribution towards ethylene and/or PA appears to differ during the development of the endocarp, as the only peak of free-Put (detected in S2) coincided with the highest ACC accumulation and ethylene production. On the contrary, in S3 it is probable that SAM was transformed preferentially into PA, given that free-Spd and Spm, hardly detectable in S1 and S2, peaked in this phase in which there was no gas production.     

Involvement of polyamines in the drought resistance of rice

This study investigated whether and how polyamines (PAs) in rice (Oryza sativa L.) plants are involved in drought resistance. Six rice cultivars differing in drought resistance were used and subjected to well-watered and water-stressed treatments during their reproductive period. The activities of arginine decarboxylase, S-adenosyl-L-methionine decarboxylase, and spermidine (Spd) synthase in the leaves were significantly enhanced by water stress, in good agreement with the increase in putrescine (Put), Spd, and spermine (Spm) contents there. The increased contents of free Spd, free Spm, and insoluble-conjugated Put under water stress were significantly correlated with the yield maintenance ratio (the ratio of grain yield under water-stressed conditions to grain yield under well-watered conditions) of the cultivars. Free Put at an early stage of water stress positively, whereas at a later stage negatively, correlated with the yield maintenance ratio. No significant differences were observed in soluble-conjugated PAs and insoluble-conjugated Spd and Spm among the cultivars. Free PAs showed significant accumulation when leaf water potentials reached -0.51 MPa to -0.62 MPa for the drought-resistant cultivars and -0.70 MPa to -0.84 MPa for the drought-susceptible ones. The results suggest that rice has a large capacity to enhance PA biosynthesis in leaves in response to water stress. The role of PAs in plant defence to water stress varies with PA forms and stress stages. In adapting to drought it would be good for rice to have the physiological traits of higher levels of free Spd/free Spm and insoluble-conjugated Put, as well as early accumulation of free PAs, under water stress.     

Stress-dependent accumulation of spermidine and spermine in the halophyte Mesembryanthemum crystallinum under salinity conditions

We studied the effects of chloride salinity (300 and 500 mM NaCl) on the content of free polyamines (PAs) from putrescine (Put) family in Mesembryanthemum crystallinum L. leaves and roots. The contents of Put and spermidine (Spd) in leaves increased temporarily, achieving the highest values on the third day of salinity treatment; thereafter (by days 7–14), they dropped sharply. The content of spermine (Spm) increased gradually, and its high level was maintained until the end of experiment. The dynamics of Spm accumulation in leaves under salinity conditions resembled that of phosphoenolpyruvate carboxylase (PEPC), a key enzyme of the water-saving CAM pathway of photosynthesis. This indicates indirectly the involvement of Spm in the common ice plant adaptation to salinity. A decrease in the molar ratios of Spd to Spm in the leaves under salinity conditions could point to the acceleration of Spm biosynthesis (accumulation) during plant adaptation, whereas the levels of Spm precursors, Put and Spd, did not increase. This phenomenon could be explained by an accelerated conversion of Spd into Spm, an active liberation of free Spm from its conjugates, or changes in the rates of studied PA biosynthesis and degradation under salinity. At the same time, the intracellular concentration of ethylene rose under these conditions. It was supposed and then demonstrated, that the pathway of ethylene biosynthesis and that of the synthesis of Put family PAs compete under severe salinity conditions. This competition might be based on the disturbances in sulfur metabolism and a decrease in the methionine content, an immediate precursor of S-adenosyl-L-methionine.     

Protective role of exogenous polyamines on salinity-stressed rice (Oryza sativa) plants

Salt-tolerant Pokkali rice plants accumulate higher polyamines (PAs) such as spermidine (Spd) and spermine (Spm) in response to salinity stress, while the sensitive cultivar M -1–48 is unable to maintain high titres of these PAs under similar conditions. The effects of the triamine Spd and the tetramine Spm on physiological and biochemical changes in 12-day-old rice seedlings were investigated during salinity stress to determine whether they could protect the sensitive plants from stress effects. At physiological concentrations Spd and Spm significantly prevented the leakage of electrolytes and amino acids from roots and shoots induced by salinity stress. To different degrees they also prevented chlorophyll loss, inhibition of photochemical reactions of photosynthesis as well as downregulation of chloroplast-encoded genes like psbA , psbB , psbE and rbcL , indicating a positive correlation between salt tolerance and accumulation of higher PAs in rice. The inhibitory effect of salinity stress and its reversal by exogenous PAs were more pronounced in the salt-sensitive M -1–48 plants than in the tolerant Pokkali plants.     

外源腐胺对根际低氧胁迫下黄瓜幼苗多胺和抗氧化系统的影响

采用营养液栽培,研究了外源腐胺(Put)对根际低氧胁迫下黄瓜幼苗体内多胺含量和抗氧化系统的影响.结果显示,低氧胁迫显著刺激了黄瓜幼苗体内活性氧(ROS)和内源多胺含量的增加,提高了抗氧化酶活性;外源Put进一步提高了低氧胁迫下黄瓜幼苗体内多胺的含量和抗氧化酶活性,降低了ROS含量,从而缓解了低氧胁迫的伤害作用;Put合成抑制剂D-精氨酸(D-Arg)不仅显著抑制黄瓜幼苗体内多胺的合成,而且抑制抗氧化酶活性,同时ROS大量积累,进一步抑制黄瓜幼苗的生长;而外源Put可缓解D-Arg的抑制作用;Put转化抑制剂甲基乙二醛-双(脒基腙)(MGBG)和Put降解抑制剂氨基胍(AG)的混合施用造成游离态Put的过量积累,以及亚精胺(Spd)、精胺(Spm)含量和抗氧化酶活性的显著降低,造成ROS大量积累,进一步加重了低氧胁迫对植株的伤害.结果表明,低氧胁迫下外源Put可提高黄瓜幼苗体内游离态Put含量,促进游离态Put向Spd和Spm转化,Spd、Spm含量的增加以及(free-Spd free-Spm)/free-Put比值的升高有利于提高植株抗氧化酶活性,增强清除ROS的能力,降低膜脂过氧化的伤害,从而增强植株的低氧胁迫耐性.     

Polyamine and nitric oxide levels relate with morphogenetic evolution in somatic embryogenesis of <Emphasis Type="Italic">Ocotea catharinensis</Emphasis>

In this study we examined the effect of polyamines (PAs) putrescine (Put), spermidine (Spd) and spermine (Spm) on growth, morphology evolution, endogenous PAs levels and nitric oxide (NO) release in Ocotea catharinensis somatic embryo cultures. We observed that Spd and Spm reduced culture growth, permitted embryo morphogenetic evolution from the earliest to last embryo development stages, increased endogenous PAs levels, and induced NO release in O. catharinensis somatic embryos. On the other hand, Put had little effect on these parameters. Spd and Spm could successfully be used to promote somatic embryo maturation in O. catharinensis. The results suggest that Spd and Spm have an important role during the growth, development and morphogenetic evolution of somatic embryos, through alterations in the endogenous nitric oxide and PAs metabolism in this species.