Endo-β-mannanases in the endosperm of germinated tomato seeds

Three forms of galactomannan-hydrolyzing enzymes (dyed galactomannan as substrate) were partially purified from germinated tomato [ Lycopersicon esculentum (L.) Mill.] seed. Two of the enzymes were of the same molecular mass, 38 kDa, as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), but the points of elution from a CM-Toyopearl column by a pH-gradient were different between the two (pH 5.15 and 5.45. respectively). The molecular mass of the third form was slightly less (37.5 kDa) than that of the other two. These 3 enzymes showed no α-galactosidase (EC 3.2.1.22) or β-mannosidase (EC 3.2.1.25) activity. Thin-layer chromatography (TLC) revealed that the products of the reaction were oligosaccharides and that free galactose and mannose were not released. These results indicate that the 3 galactomannan-hydrolyzing enzymes are endo-β-mannanases (EC 3.2.1.78). Polyclonal antibodies raised against the 37.5-kDa polypeptide cross-reacted with the two 38-kDa polypeptides, indicating that the 3 endo-β-mannanases are immunologically homologous. Activity staining and immunoblotting of native PAGE of endosperm extracts revealed that only two (38-kDa. elution point pH 5.15 and 37.5-kDa proteins) of the 3 forms were major endo-β-mannanases present in the endosperm of germinated tomato seeds.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

The role of endogenous gibberellin in seed and fruit development of tomato: Studies with a gibberellin-deficient mutant

The role of endogenous gibberellin (GA) in seed and fruit development was studied with the use of the GA-deficient ga-1 mutant of tomato ( Lycopersicon esculentum Mill. cv. Moneymaker). Flowers of the ga-1 mutant were abnormal and sterile, but parthenocarpic fruit development was observed occasionally on the dwarf plants. A single application of GA₄₊₇ restored the fertility of the mutant flowers and resulted in seed set. Development of GA-producing and GA-deficient seeds in GA-deficient fruits was compared by pollination of ga-1/ga-1 flowers with wild-type or ga-1 pollen, respectively. In ga-1/ga-1 seed dehydration started about 1 week earlier than in Ga-1/ga-1 seeds. Ultimate fresh and dry weights of mature Ga-1/ga-1 seeds were higher than those of ga-1/ga-1 seeds and showed negative correlations with the total number of seeds per fruit. Total content and composition of seed proteins were not influenced by the GA-deficiency. Germination of the mature seeds depended on embryonal GA synthesis and was not influenced by maternal GA production. Final fresh weight of the ga-1/ga-1 fruits was positively correlated with the number of seeds per fruit. In these fruits, the minimum number of seeds for growth above the parthenocarpic level was about 10 or 35 in the presence of Ga-1/ga-1 or ga-1/ga-1 seeds, respectively. Fruits containing GA-producing seeds reached a higher fresh weight than those containing GA-deficient seeds, and their ripening was delayed by one week. It is concluded that gibberellin is indispensable for the development of fertile flowers and for seed germination, but only promoting in later stages of fruit and seed development.     

The effect of light and exogenous gibberellic acid on respiration pathways during germination of tomato seeds

Tomato (Lycopersicon esculenlum Mill. cv. Taiwan Red) seeds are typical lightsensitive seeds where light requirement can be substituted by gibberellic acid (GA₃). During the initial stage of germination, the hexose monophosphate pathway (HMP) in seeds incubated for 24 h under white light or 12 h in 0.3 mW GA₃ solution acidified with 1 M HCI for 1 h in the dark (HCl→GA₃) was much greater than in seeds incubated for 24 h in the dark. The results were obtained from measurements of the respiration rate by man metric method of Warburg with or without iodoacetic acid, and from activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and aldolase (EC 4.1.2.13). Although the HMP tended to decrease at the later stage (72 h under white light or in the dark, or 36 h in HCl→GA₃), it remained greater in light- than in dark-incubated seeds. CN-resistant respiration increased from 27–30% to 57–64% of the total respiration in seeds incubated under white light or in HCI→GA₃, while respiration of non-germinating, dark-incubated seeds remained zero. Benzohydrox–amic acid (BHAM), an inhibitor of the alternative pathway, inhibited both respiration and seed germination. It is concluded that the enhancement of HMP and the CN–resistant pathways are both controlled by P_fr, but there is no direct connection between them.     

Priming of seeds with NaCl induces physiological changes in tomato plants grown under salt stress

The effects of seed priming with 6 M NaCl solution have been investigated with respect to growth and physiological responses of tomato plants ( Lycopersicon esculentum Mill. cv. Pera) exposed to 70 and 140 m M NaCl nutrient solutions from 11 to 60 days after sowing. Tomato seedlings from primed seeds emerged earlier than from non-primed seeds. At 70 m M , a lower shoot and root dry weight reduction was found in plants from primed seeds at the different harvests (30, 45 and 60 days after sowing), while at 140 m M the positive effect of seed priming was only shown in roots. Significant changes in Na⁺ and CI⁻ accumulation with seed priming were only found in roots at 60 days after sowing, with ion accumulation in roots being higher in plants grown at 70 and 140 m M from primed seeds. In leaves of salt-treated plants, significant increases in sugars and organic acids with seed priming were found from 30 days after sowing, and these increases were higher at longer treatment times. In roots, however, only the organic acids tended to increase in plants from primed seeds, although they increased less than in leaves, especially at 60 days after sowing. These results support the hypothesis that priming of seeds with NaCl induces physiological changes in the plants, changes which are shown more clearly at advanced growth stages.     

Galactomannan hydrolyzing activity develops during priming in the micropylar endosperm tip of tomato seeds

Development of galactomannan hydrolyzing activity was followed in seeds of tomato [ Lycopersicon esculentum (L.) Mill. cv. Toyonishiki] during priming and germination. The activity developed in seeds that were being primed in polyethylene glycol (-0.8 MPa). The activity was detected exclusively in the endosperm portion just adjacent to the radicle tip. Part of the activity remained active after desiccation of the primed seeds. After transfer to water, the activity in the primed seeds immediately began to increase, while in unprimed seeds the beginning of the increase in activity was delayed by about 1 day. In scanning electron microscopy, the inner surface of the cell walls of the micropylar endosperm portion appeared eroded in primed seeds that had been imbibed in water for 16 h (before germination), but not in unprimed seeds imbibed for the same period. These results support the hypothesis that galactomannan hydrolyzing enzyme, which is believed to be responsible for breakdown of tomato endosperm cell walls and hence for the weakening of mechanical restraint against radicle growth, may be involved in the improved germination of primed tomato seeds.     

Ageing of tomato seeds involves glutathione oxidation

The effect of seed ageing on the oxidation of reduced glutathione (GSH) and the role of GSH oxidation in ageing-induced deterioration were studied in seeds of tomato ( Lycopersicon esculentum Mill. cv. Lerica, Moneymaker and Cromco). Both long-term storage at 15°C/30% relative humidity (RH) and artificial ageing at 20°C/75% RH, 30°C/45% RH and 60°C/45% RH resulted in a marked loss of GSH and a simultaneous, though not proportional, increase in its oxidized form GSSG. The glutathione thiol-disulfide status shifted towards a highly oxidized form, while the total glutathione pool decreased. The extent of GSH oxidation differed between ageing conditions and was not directly related to the extent of seed deterioration. Thiobarbituric acid-reactive substances did not increase in ageing tomato seeds, suggesting that lipid peroxidation did not take place. Hydration of seeds, either upon imbibition in water or by priming in an osmotic solution, resulted in a rapid decrease in GSSG, a shift of the glutathione redox couple to a mainly reduced status and an increase in the glutathione pool, in both control and aged seeds. The results indicate that, in tomato seeds, (1) seed ageing involves GSH oxidation into GSSG, which is indicative of oxidative stress, (2) ageing does not affect the GSSG reduction capacity upon subsequent imbibition, and (3) the lowered viability of aged seeds cannot directly be ascribed to the decreased GSH pool or To the highly oxidized glutathione redox status.     

An experimental assessment of the factors influencing Agrobacterium-mediated transformation in tomato

Agrobacterium tumefaciens strain LBA4404 carrying a binary vector pTOK233, which contained the GUS reporter gene and a kanamycin-resistance gene nptII, was employed for optimizing the transformation efficiency evaluated by a GUS gene transient expression level. Eight factors including explant types, explant size and source, the concentration of cytokinin, inoculation time, pH of inoculation and cocultivation media, bacterial concentration, acetosyringone concentration, and cocultivation duration were investigated in detail. This optimized protocol was then adopted to obtain transgenic tomato plants resistant to cucumber mosaic virus (CMV) mediated by Agrobacterium tumefaciens, strain LBA4404, carrying a binary vector pR-ΔGDD containing the kanamy cin-resistance gene and CMV replicase gene with GDD deletion. The presence of the CMV-RNA2 gene was confirmed by genomic DNA Southern blot analysis in all transformants analyzed. Field spray test showed that the transgenic tomato plants were resistant to 100 mg/l kanamycin. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 2, pp. 280–284. The text was submitted by the authors in English.     

No difference in the regulation pattern of calcium on ethylene biosynthesis between wild-type and never-ripe tomato fruit at mature green stage

This work investigated how calcium regulates the ethylene biosynthesis in the fruits of wild-type tomato (Lycopersicon esculentum L.) and their ethylene receptor never-ripe (Nr) mutants. In Nr tomato, the ethylene perception was blocked. When both materials were treated with calcium, the content of 1-aminocyclopropane-1-carboxylic acid (ACC)/malonyl-ACC and the activity of ACC oxidase (ACO) in tomato fruit discs increased, whereas the production of ethylene, content of malondialdehyde, and membrane permeability decreased. Calcium treatment did not affect the activity of ACC synthase, which is the first committed step in the ethylene biosynthesis pathway. The expression of LeACO1 in mature green fruit was inhibited significantly by calcium treatment in wild-type and Nr tomatoes, but the expression of LeACS2, the key ACC synthase gene in ethylene synthesis during tomato fruit maturing, was not affected. These results revealed that the effect of calcium on ethylene biosynthesis in tomato mature green fruit was independent of ethylene perception. The results also revealed that the targeting step of calcium preventing ethylene production was located at the ACC conversion to ethylene, by means of inhibiting ACC availability for ACO through enhancing cell membrane integrity and by means of preventing LeACO1 gene expression. Published in Russian in Fiziologiya Rastenii, 2006, Vol. 53, No. 1, pp. 60–67. The text was submitted by the authors in English.     

Effect of light and temperature on the germination of lettuce seeds

A short period (15–30 min) at 30° C promotes germination of seeds of Lactuca sativa L. cv. Repolhuda in darkness. Far-red light reverses this stimulation, and the escape curves for phytochrome and high-temperature action are quite similar, indicating that the two factors act at a common point in the chain of events leading to germination. It is suggested that high temperature acts by decreasing the threshold of the active, far-red absorbing, form of phytochrome (Pfr) needed to promote germination.Abbreviations FR far-red light - Pfr far-red-absorbing form of phytochrome - R red light     

The influence of temperature during seed development on the germination characteristics of millet seeds

Abstract. The cardinal temperatures, rate of germination and final percentage germination of pearl millet seeds were measured for seeds raised in greenhouses maintained at mean air temperatures of 19, 22, 25, 28 and 31°C. The results showed that cardinal temperatures for germination are unaffected by the temperature during seed development and growth. However, the conditions during seed growth did affect seed size and, subsequently, germination rate and seed viability.     

磁场处理蕃茄种子对幼苗CAT、POD酶活性影响

磁场处理蕃茄种子,观察种子的发芽率幼苗的过氧化氢酶（ＣＡＴ）和过氧化物酶（ＰＯＤ）活性的变化,结果,磁场强度在１０００～２０００ＧＳ范围内,种子发芽率最高,幼苗的过氧化氢酶的过氧化物酶的活性也最高,磁场强度高于３０００ＧＳ以上时,种子发芽率和幼苗酶活性随之降低。     

Growth rate, plant development and water relations of the ABA-deficient tomato mutant sitiens

Given the close relationship between a plant's growth rate and its pattern of biomass allocation and the effects of abscisic acid (ABA) on biomass allocation, we studied the influence of ABA on biomass allocation and growth rate of wildtype tomato ( Lycopersicon esculentum Mill. cv. Moneymaker) plants and their strongly ABA-deficient mutant sitiens. The relative growth rate of sitiens was 22% lower than that of the wildtype, as the result of a decreased specific leaf area. The net assimilation rate and the leaf weight ratio were not affected. The mutant showed a much higher transpiration rate and lower hydraulic conductance of the roots. These two factors resulted in sitiens having a significantly lower leaf water potential and turgor. resulting in reduced leaf expansion and, consequently, a lower specific leaf area relative to the wildtype. Addition of ABA to the sitiens roots resulted in phenotypic reversion to the wildtype. We conclude that the influence of ABA-deficiency on biomass allocation and relative growth rate is the result of altered water relations in the plants, rather than of a direct effect on sink strength of different plant organs.     

Exudation of an allelopathic substance lepidimoide from seeds during germination

Lepidimoide promotes growth of the cockscomb hypocotyl. It is exuded from germinating seeds of various plant species into their culture environment. The mode of exudation of lepidimoide from seeds into the culture solution, using sunflower and buckwheat seeds, was studied in relation to seed germination. In the dry seeds, about 75% of the lepidimoide was found in the seed coat and about 25% in the kernel. Upon water imbibition it was released into the culture solution. However, the quantity of lepidimoide detected in the seed exudate was more than three times the total amount in dry and imbibed seeds, suggesting that lepidimoide was also produced de novo in the seeds and subsequently released. When seed coats or kernels were imbibed separately, the quantity of lepidimoide released from the seed coats into the culture solution was much the same as that in the dry seeds, but the amount of lepidimoide detected in the exudate of kernels was about 16 times that in the dry kernels. These results suggest that lepidimoide, already present in dry seeds, as well as that newly produced in the kernels following imbibition, was released into the environment.     

Effects of agar concentration on water status and growth of rose plants cultured in vitro

The role of endogenous abscisic acid (ABA) in seed development was studied with the use of the ABA-deficient sit ^w ( sitiens ) mutant of tomato ( Lycopersicon esculentum Mill. cv. Moneymaker). The sit ^w mutation causes a strong reduction of the endogenous ABA level in the developing seed. Reciprocal crosses of wild-type and the sit ^w mutant show a dual origin of ABA. The genotype of the mother plant regulates the ABA content present in the testa, which shows a peak half-way through seed development. The genotype of the embryo and endosperm is responsible for a second ABA fraction, present in these tissues. This second fraction reaches its peak during the second half of seed development. The strong reduction of endogenous ABA level in the developing sit ^w / sit ^w seed does not change the final fresh and dry weights of the seed nor the accumulation and composition of storage proteins.