Abscisic Acid and its relationship to seed filling in soybeans

The effect of exogenous abscisic acid (ABA) on the rate of sucrose uptake by soybean (Glycine max L. Merr.) embryos was evaluated in an in vitro system. In addition, the concentrations of endogenous ABA in seeds of three soybean Plant Introduction (PI) lines, differing in seed size, were commpared to their seed growth rates. ABA (10⁻⁷ molar) stimulated in vitro sucrose uptake in soybean (cv `Clay') embryos removed from plants grown in a controlled environment chamber, but not in embryos removed from field-grown plants of the three PI lines. However, the concentration of ABA in seeds of the three field-grown PI lines correlated well with their in situ seed growth rates and in vitro [¹⁴C] sucrose uptake rates.

Across genotypes, the concentration of ABA in seeds peaked at 8.5 micrograms per gram fresh weight, corresponding to the time of most rapid seed growth rate, and declined to 1.2 micrograms per gram at physiological maturity. Seeds of the large-seeded genotype maintained an ABA concentration at least 50% greater than that of the small-seeded genotype throughout the latter half of seed filling. A higher concentration of ABA was found in seed coats and cotyledons than in embryonic axes. Seed coats of the large-seeded genotype always had a higher concentration of ABA than seed coats of the small-seeded line. It is suggested that this higher concentration of ABA in seed coats of the large-seeded genotype stimulates sucrose unloading into the seed coat apoplast and that ABA in cotyledons may enhance sucrose uptake by the cotyledons.

     

Carbohydrate Changes during Maturation of Cucumber Fruit : Implications for Sugar Metabolism and Transport

Changes in the carbohydrate profiles in the mesocarp, endocarp, and seeds of maturing cucumber (Cucumis sativus, L.) fruit were analyzed. Fruit maturity was measured by a decrease in endocarp pH, which was found to correlate with a loss in peel chlorophyll and an increase in citric acid content. Concentrations of glucose and fructose (8.6-10.3 milligrams per gram fresh weight, respectively) were found to be higher than the concentration of sucrose (0.3 milligrams per gram fresh weight) in both mesocarp and endocarp tissue. Neither raffinose nor stachyose were found in these tissues. The levels of glucose and fructose in seeds decreased during development, but sucrose, raffinose, and stachyose accumulated during the late stages of maturation. Both raffinose and stachyose were found in the seeds of six lines of Cucumis sativus L. This accumulation of raffinose saccharides coincided with an increase in galactinol synthase activity in the seeds. Funiculi from maturing fruit were found to be high in sucrose concentration (4.8 milligrams per gram fresh weight) but devoid of both raffinose and stachyose. The results indicated that sucrose is the transport sugar from the peduncle to seed, and that raffinose saccharide accumulation in the seed is the result of in situ biosynthesis and not from direct vascular transport of these oligosaccharides into the seeds.     

Effect of Water Deficits on Seed Development in Soybean : II. Conservation of Seed Growth Rate

Water deficits during seed filling decrease seed size in soybean (Glycine max L.). This may result from a reduction in the supply of assimilates from the maternal plant and/or an inhibition of seed metabolism. To determine whether maternal or zygotic factors limited seed growth, we examined the effects of a plant water deficit on the supply of sucrose to and its utilization by developing embryos. Plants were grown in the greenhouse, and water deficits were imposed by withholding water for a period of 6 days during linear seed fill. When water was withheld, leaf water potential decreased rapidly, inhibiting canopy photosynthesis completely within 3 days. However, seed dry weight (nodes 7-11) continued to increase at or near the control rate. The level of total extractable carbohydrates in leaf, stem, and pericarp tissue decreased by 70, 50, and 45%, respectively, indicating that reserves were mobilized to support seed growth. Cotyledon sucrose content decreased from about 60 milligrams per gram dry weight to 30 milligrams per gram dry weight. Similarly, the concentration of sucrose in the interfacial apoplast of the cotyledons decreased from approximately 100 millimolar to 50 millimolar. However, the rate of sucrose accumulation by excised embryos, measured in a short-term in vitro assay, increased in response to the water deficit. These results indicate that both source and sink activity in soybean are altered by water deficits to maintain the flux of assimilates to the developing embryos. This may explain why seed growth is maintained, albeit for a shorter duration, when soybean is exposed to water deficits during the seed filling period.     

Abscisic Acid in Developing Zygotic Embryos of Theobroma cacao

Abscisic acid (ABA) levels were measured by enzyme-linked immunosorbent assay in developing zygotic embryos of Theobroma cacao. ABA was detected in all embryos tested, with a peak of ABA at levels of 1 to 3 micrograms per gram fresh weight during early maturation. This corresponded to embryos of 10 to 30% dry weight and to early stages of anthocyanin and lipid accumulation.     

Solute Accumulation and Compartmentation during the Cold Acclimation of Puma Rye

During cold acclimation of Puma rye (Secale cereale L. cv Puma), the intracellular osmotic potential nearly doubles. During this period, the accumulation of glycinebetaine, proline, and soluble sugars was monitored. The amount of glycinebetaine increased from 290 to 1300 micrograms per gram fresh weight during the 4-week acclimation period. Proline content did not change during the first 3 weeks of acclimation but then increased from 27 to 580 micrograms per gram fresh weight during the next 3 weeks. The total soluble sugar content more than doubled by the second week of cold acclimation, increasing from 11 to 26 milligrams per gram fresh weight. Most of this increase can be attributed to the accumulation of sucrose and raffinose, whose levels increased from 2.4 and 0 to 11 and 5 milligrams per gram fresh weight, respectively. The content of monosaccharides, predominantly glucose, remained at a constant 10 milligrams per gram fresh weight throughout the acclimation period. A comparison of the sugar content of protoplasts versus vacuoles isolated from cold-acclimated leaves revealed that the extravacuolar volume contained monosaccharides, sucrose, and raffinose. Thus, the increased amounts of sucrose and raffinose that occur during cold acclimation are present in compartments external to the vacuole and may contribute to cryoprotection.     

Photoperiodically Induced Changes in Seed Growth Rate of Soybean as Related to Endogenous Concentrations of ABA and Sucrose in Seed Tissues

Short-day photoperiods can increase the partitioning of assimilatesto filling seeds of soybean (Glycine max L. Merr.), resultingin higher seed growth rates. The plant growth substance ABAhas been implicated in the regulation of assimilate transferwithin filling soybean seeds. Thus, we hypothesized that anincreased concentration of endogenous ABA in seeds may enhancesucrose accumulation and seed growth rate of soybeans exposedto short-day photoperiods. Plants of cv. Hood 75 were grownin a greenhouse under an 8-h short-day photoperiod (SD) until11 d after anthesis (DAA) of the first flower, when half ofthe plants were transferred to a night-interruption (NI) treatment(3 h of low-intensity light inserted into the middle of thedark period). Plants remaining in SD throughout seed developmenthad seed growth rates 43% higher than that of plants shiftedto NI (7·6 mg seed^–1 d^–1 vs. 5·3 mgseed^–1 d^–1). On a tissue-water basis, the concentrationof ABA in SD seeds increased rapidly from 7.6 µmol l^–1at 11 DAA to 65·2 µmol l^–1 at 18 DAA, butthen declined to 6·6 µmol l^–1 by 39 DAA.In contrast, the concentration of ABA increased more slowlyin NI seeds, reaching only 47·4 µmol l^–1by 18 DAA, peaking at 57·0 µmol l^–1 on 25DAA, and declining to 10·2 µmol l^–1 by 39DAA. The concentration of sucrose in SD embryos peaked at 73·5mmol l^–1 on 25 DAA and remained relatively constant forthe remainder of the seed-filling period. In NI, the concentrationof sucrose reached only 38·3 mmol 1^–1 by 25 DAA,and peaked at 61·5 µmol l^–1 on 32 DAA. Thusin both SD and NI, sucrose accumulated in embryos only afterthe peak in ABA concentration, suggesting that ABA may havestimulated sucrose movement to the seeds. The earlier accumulationof ABA and sucrose in SD suggests that ABA may have increasedassimilate availability during the critical cell-division period,thus regulating cotyledon cell number and subsequent seed growthrate for the remainder of the seed-filling period. Glycine max L. Merr. cv. Hood 75, soybean, assimilate partitioning, abscisic acid, photoperiod, source-sink     

Precocious Germination during In Vitro Growth of Soybean Seeds

Immature Glycine max (L.) Merrill seeds were grown and matured in liquid medium at 25°C under fluorescent light. In standard medium containing minerals, 146 millimolar sucrose and 62.5 millimolar glutamine (osmolality 0.24), precocious germination seldom occurred with a starting seed size of less than 300 milligrams fresh weight. Frequency of precocious germination increased with increased starting seed size. Sucrose concentration strongly affected precocious germination while glutamine concentration had no effect. Starting with 300 to 350 milligrams fresh weight seeds, treatments which reduced the sucrose concentration or lowered the osmolality of the culture medium stimulated precocious germination, and increased the fresh weight growth but not the dry weight growth of seeds. Increasing the osmolality to 0.38 with sucrose or mannitol prevented precocious germination without reducing dry weight accumulation in seeds. In medium with initially low osmolality, precocious germination was inhibited by addition of 1 to 100 micromolar abscisic acid to the medium without a reduction in seed growth. During growth and maturation of large soybean seeds in vitro, precocious germination and other abnormal tissue growth can be prevented by high sucrose or mannitol concentrations in the medium or by addition of abscisic acid.     

Relationship between Stress-Induced ABA and Proline Accumulations and ABA-Induced Proline Accumulation in Excised Barley Leaves

When excised second leaves from 2-week-old barley (Hordeum vulgare var Larker) plants were incubated in a wilted condition, abscisic acid (ABA) levels increased to 0.6 nanomole per gram fresh weight at 4 hours then declined to about 0.3 nanomole per gram fresh weight and remained at that level until rehydrated. Proline levels began to increase at about 4 hours and continued to increase as long as the ABA levels were 0.3 nanomole per gram fresh weight or greater. Upon rehydration, proline levels declined when the ABA levels fell below 0.3 nanomole per gram fresh weight.

Proline accumulation was induced in turgid barley leaves by ABA addition. When the amount of ABA added to leaves was varied, it was observed that a level of 0.3 nanomole ABA per gram fresh weight for a period of about 2 hours was required before proline accumulation was induced. However, the rate of proline accumulation was slower in ABA-treated leaves than in wilted leaves at comparable ABA levels. Thus, the threshold level of ABA for proline accumulation appeared to be similar for wilted leaves where ABA increased endogenously and for turgid leaves where ABA was added exogenously. However, the rate of proline accumulation was more dependent on ABA levels in turgid leaves to which ABA was added exogenously than in wilted leaves.

Salt-induced proline accumulation was not preceded by increases in ABA levels comparable to those observed in wilted leaves. Levels of less than 0.2 nanomole ABA per gram fresh weight were measured 1 hour after exposure to salt and they declined rapidly to the control level by 3 hours. Proline accumulation commenced at about 9 hours. Thus, ABA accumulation did not appear to be involved in salt-induced proline accumulation.

     

Abscisic Acid Levels in Soybean Reproductive Structures during Development

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

不同发育时期黄皮种子脱水敏感性的研究

自花后４６ｄ到８８ｄ果实成熟．黄皮种子的发芽率由０升至１００％．而活力指数逐渐上升,到花后７４ｄ达到最大值,之后略有下降．每粒种子的呼吸强度在花后４６－６７ｄ持续增加,此后则渐渐减弱,但湿藏２ｄ后又回升．黄皮种子的发育明显超前于果实．花后７４ｄ时．每粒种子的干重已接近最大值,这时种子活力最大．而果实的鲜重虽然已接近最大值．但其干重却只有成熟时的７３％。花后４６－５３ｄ的种子,其发芽率小于１００％,轻微脱水能提高种子的发芽率及活力指数,花后６０ｄ至果实成熟．种子发芽率均为１００％．这时任何程度的脱水都会引起活力指数的下降,但不同发育时期的黄皮种子耐脱水力有差别．其中以花后６７ｄ的耐脱水力最强．花后８８ｄ果实成熟时种子的耐脱水力最弱。     

Endosperm protein of wheat seed as a determinant of seedling growth

Seed of a Mexican semidwarf wheat (Triticum aestivum L. cv. Inia 66), was obtained from a nitrogen fertilizer field trial grown in Mexico. A high positive correlation was obtained between seed protein content and seedling dry weight after 3 weeks growth (r = +0.92^**). The seedling dry weight was positively related to the protein content of the aleurone layer and endosperm, but not to the embryo. Small, 35 milligrams, high protein seeds (4.7 milligrams protein per seed) produced larger seedlings than large, 45 milligrams, low protein seeds (4.3 milligram protein per seed). There was no difference in the weight or protein content of embryos from low and high protein seeds and their growth was similar. Composite seeds of the two protein levels were produced by transferring embryos from one endosperm type to the other. After 4 weeks, there was no difference between the different embryo types grown on the same endosperm type. High protein endosperm produced more vigorous seedlings regardless of the embryo type grown on it, indicating that the factor(s) responsible for the greater growth of high protein seed is in the endosperm.     

Relationships between Respiration Rate and Adenylate and Carbohydrate Pools of the Soybean Fruit

Relationships between respiration rate and adenylate and carbohydrate pools of the soybean (Glycine max L. Merrill) fruit during rapid seed growth were evaluated. Plants at mid pod-fill were subjected to different concentrations of CO(2) to alter the amount of photosynthate produced and, thus, available to the fruit. Respiration rate of the intact fruits was measured, along with glucose, sucrose, and starch concentrations, adenylate energy charge (AEC), and total adenylate pool (SigmaAdN) in the pod wall, seed coat, and cotyledons. The concentration of sucrose remained relatively constant in the pod wall (1.0 milligram per 100 milligrams dry weight), seed coat (6.5 milligrams per 100 milligrams dry weight), and cotyledons (4.5 milligrams per 100 milligrams dry weight) at moderate and high respiration rates. Furthermore, AEC remained relatively constant in the pod wall (0.55), seed coat (0.24), and cotyledons (0.44) during changes in respiration rate. This suggests that the amount of assimilate transported to the fruit, and its flux through the sucrose pools of the fruit parts, were important in the regulation of the respiration rate of the fruit. The average SigmaAdN in the seed coat (1300 picomoles per milligram dry weight) was significantly greater than in the cotyledons (750 picomoles per milligram dry weight) and pod wall (300 picomoles per milligram dry weight). In addition, the SigmaAdN in the seed coat and cotyledons increased with increasing respiration rate of the fruit. The high SigmaAdN in the seed coat and its increase with increases in respiration rate of the fruit suggest that an energy-requiring process is involved in the movement of sucrose through the seed coat.     

Stimulation of Isopentenyl Pyrophosphate Incorporation into Polyisoprene in Extracts from Guayule Plants (Parthenium argentatum Gray) by Low Temperature and 2-(3,4-Dichlorophenoxy) Triethylamine

Rubber particles isolated from guayule (Parthenium argentatum Gray) stem homogenates contain a polyprenyl transferase which catalyzes the polymerization of isopentenyl pyrophosphate into polyisoprene. The polymerization reaction is stimulated with the addition of an allylic pyrophosphate initiator and forms a polymer of polyisoprene with a molecular weight distribution from 10³ to 10⁷. The polymerization reaction in crude stem homogenates is not affected by the addition of an initiator probably due to the high activity of isopentenyl pyrophosphate isomerase furnishing saturating levels of dimethylallyl pyrophosphate. Polyisoprene formation in stems of guayule plants exposed to cold winter temperatures increased from 15.4 milligrams per gram dry weight in October to 24.5 milligrams per gram dry weight in January and increased from 16.2 to 38.1 milligrams per gram dry weight in the same period by additionally treating the plants with 5000 ppm of 2-(3,4-dichlorophenoxy)triethylamine. The rate of polymerization of isopentenyl pyrophosphate into polyisoprene in stem homogenates of the cold treated plants increased from 12.1 nanomoles per hour per gram fresh weight in October to 144.3 nanomoles per hour per gram fresh weight in January and increased from 17.7 to 446.8 nanomoles per hour per gram fresh weight in the same period by additionally treating the plants with 5000 ppm of 2-(3,4-dichlorophenoxy)triethylamine. These results show that the increase in polyprenyl transferase activity partially accounts for the increase in polyisoprene synthesis in guayule plants exposed to low temperature and treated with 2-(3,4-dichlorophenoxy)triethylamine.     

重穗型杂交水稻籽粒灌浆过程中强势和强势颖花内源IAA、ABA和GA水平的动态状况

研究了重穗型杂交水稻培矮 6 4s/E3 2的灌浆过程和强、弱势颖花中内源IAA、ABA和GA1 GA3水平的动态状况。籽粒发育过程中不同内源激素水平高低依次为 :IAA >GA1 GA3>ABA。IAA和ABA水平在强势颖花中较高而GA1 GA3水平在弱势颖花中较高。 3种激素水平的变化与谷粒增重速率之间均存在正相关 ,两个最高的相关系数值分别存在于单位鲜重样本的IAA含量(ng/gFW ) 与籽粒鲜重的增重速率之间 (r =0 .82 1 8 )和单个籽粒IAA含量 (ng/grain)与籽粒干重的增重速率之间 (r =0 .8485 )。推测启动和维持籽粒灌浆过程可能需要较高的IAA水平 ;ABA可能具有促进籽粒中同化物的累积和种子成熟的作用 ;GA1 GA3可能具有保持弱势颖花活性的特殊作用     

重穗型杂交水稻籽粒灌浆过程中强势和弱势颖花内源IAA、ABA和GA水平的动态状况

研究了重穗型杂交水稻培矮 6 4s/E3 2的灌浆过程和强、弱势颖花中内源IAA、ABA和GA1 GA3水平的动态状况。籽粒发育过程中不同内源激素水平高低依次为 :IAA >GA1 GA3>ABA。IAA和ABA水平在强势颖花中较高而GA1 GA3水平在弱势颖花中较高。 3种激素水平的变化与谷粒增重速率之间均存在正相关 ,两个最高的相关系数值分别存在于单位鲜重样本的IAA含量(ng/gFW ) 与籽粒鲜重的增重速率之间 (r =0 .82 1 8 )和单个籽粒IAA含量 (ng/grain)与籽粒干重的增重速率之间 (r =0 .8485 )。推测启动和维持籽粒灌浆过程可能需要较高的IAA水平 ;ABA可能具有促进籽粒中同化物的累积和种子成熟的作用 ;GA1 GA3可能具有保持弱势颖花活性的特殊作用     

Abscisic acid in developing grains of wheat and barley genotypes differing in grain weight

Two genetically related wheat lines growing in cabinets were given different temperatures during grain filling, and abscisic acid (ABA) was measured in whole grains by gas chromatography with an electron-capture detector. Three genetically related barley lines grown in the field were assayed for ABA content in endosperm and embryo fractions separately by radiommunoassay.Maximum grain growth rate and final weight per grain of the two wheat lines differed by 50–60% at low temperature and 30–40% at high temperature. During grain development two peaks in ABA level were observed at low temperature but only one at high temperature. At times when differences in grain growth rate between genotypes and between temperature treatments were large, the corresponding differences in ABA concentration were small. In barley, one line (Iabo 14) had 30% heavier grains than the other two (Onice and Opale). Endosperm ABA concentrations showed no clear differences between genotypes until grain filling was nearly complete. Embryo ABA levels were up to 10-times greater than those in the endosperm, with Opale having significantly less ABA in the embryo than the other two cultivars.Our experiments did not provide evidence for a causal relationship between ABA levels during grain filling and grain growth rate or final weight.Abbreviations ABA Abscisic acid - DAA days after anthesis - DW dry weight - FW fresh weight     

Metabolism of Monoterpenes in Cell Cultures of Common Sage (Salvia officinalis) : Biochemical Rationale for the Lack of Monoterpene Accumulation

Leaves of common sage (Salvia officinalis) accumulate monoterpenes in glandular trichomes at levels exceeding 15 milligrams per gram fresh weight at maturity, whereas sage cells in suspension culture did not accumulate detectable levels of monoterpenes (<0.3 nanograms per gram fresh weight) at any stage of the growth cycle, even in the presence of a polystyrene resin trap. Monoterpene biosynthesis from [U-¹⁴C]sucrose was also virtually undetectable in this cell culture system. In vitro assay of each of the enzymes required for the sequential conversion of the ubiquitous isoprenoid precursor geranyl pyrophosphate to (+)-camphor (a major monoterpene product of sage) in soluble extracts of the cells revealed the presence of activity sufficient to produce (+)-camphor at a readily detectable level (>0.3 micrograms per gram fresh weight) at the late log phase of growth. Other monoterpene synthetic enzymes were present as well. In vivo measurement of the ability to catabolize (+)-camphor in these cells indicated that degradative capability exceeded biosynthetic capacity by at least 1000-fold. Therefore, the lack of monoterpene accumulation in undifferentiated sage cultures could be attributed to a low level of biosynthetic activity (relative to the intact plant) coupled to a pronounced capacity for monoterpene catabolism.     

The timing and rate of phytic Acid accumulation in developing soybean seeds

The time-course of phosphorus (P) accumulation in the phytic acid fraction of developing soybean (Glycine max [L.] Merr. cv `Williams 79') seeds as well as the relation of phytic acid P to total P content were determined. Phytic acid was detected early in embryogenesis in field-grown soybeans and accumulated in a linear fashion throughout most of seed development. Although the observed rates of accumulation ranged from 18.7 micrograms phytic acid P per seed per day in pods positioned low on the plant to 33.6 micrograms in pods positioned high on the plant, the final concentrations were the same in all cases. Nearly all of the P translocated to developing seeds was incorporated into phytic acid from the third week after flowering until physiological maturity, with the sum of nonphytic acid P compounds remaining constant. Phytic acid accumulation was also linear throughout development when soybean plants were grown in solutions having nutrient P levels that ranged from severely limiting (2.0 milligrams P per liter) to excess (50 milligrams P per liter). However, there was a pronounced effect on rate of accumulation, which ranged from 7.2 micrograms phytic acid per seed per day with limiting nutrient P to 44.7 micrograms with excess P. The change in level of phytic acid accounted for most of the alteration in total seed P that was caused by altering the P status of the plants. These results support the view that phytic acid synthesis is involved in P homeostasis of the developing soybean seed.     

Endogenous abscisic acid signaling towards storage reserve filling in developing seed tissues of castor bean (Ricinus communis L.)

Abscisic acid (ABA; free form) is a naturally occurring physiological growth hormone of higher plants. A detailed study involving the time course growth of developing seed tissues associated with endogenous levels of free ABA were investigated using a novel enzyme-linked immunosorbent assay. Seed filling in castor (Ricinuc communis L.) endosperm, embryo, and pod is marked with a rapid increase in fresh weight during the mid-developmental stages [21–42 days after pollination (DAP)], followed by a steady decline at the maturation stages (42–63 DAP) accompanied with a rapid lipid synthesis (in endosperm and embryo) during the same period, except for in pod. Endogenous ABA levels in endosperm (0.001–0.32 μg/g) and embryo (0.003–0.13 μg/g) followed a concurrent pattern with seed reserve filling, showing a rapid increase during the mid-developmental stages 21–42 DAP, whereas ABA levels in seed pod (0.2–22.9 μg/g) showed a different accumulation pattern with rapid increase and decline during the early-mid developmental stages, preceded by the maximal increase during the maturation stage (63 DAP). Together, our results provide evidence for the association of endogenous ABA in seed filling as well as in reserve deposition and provides clue for the effective usage of exogenous ABA concentrations in developing seeds with a focus, on improving seed reserve complex in castor.     

Treatments affecting maturation and germination of American chestnut somatic embryos

The effects of amino acids, abscisic acid (ABA), polyethylene glycol (PEG), and elevated sucrose were tested on the maturation and germination of American chestnut (Castanea dentata) somatic embryos. Somatic embryos from three lines were matured over an eight week period through a two-stage process. After maturation, somatic embryos were randomly divided into three groups to measure dry weight/ fresh weight ratios, starch levels, and germination rates. Prior to transfer to germination medium, somatic embryos received a four week cold treatment. While some treatments with amino acids, elevated sucrose, PEG or ABA increased either dry weight/fresh weight ratios, starch content or both, only addition of 25mM L-asparagine significantly increased germination rate and taproot length, and this response was only obtained with one of the three lines tested. Six plants survived the transfer to potting mix, acclimatization to greenhouse conditions and field planting.