Effects of Diurnal Changes in the Salinity of the Nutrient Solution on the Accumulation of Calcium by Tomato Fruit

Tomato fruit grown in diurnally fluctuating salinities (8 mScm^–1 during the day and 3 mS cm^–1 at night; 8/3mS cm^–1), accumulated the same amount of dry matter andmagnesium (Mg) as those in constant 3 or 8 mS cm^–1, butan intermediate amount of calcium (Ca). Raising the salinityof the nutrient solution by enriching with macronutrients orby adding NaCl had similar effects. The uptake of ⁴⁵Ca by tomato plants during the day was greaterthan at night and was reduced by salinity in both periods. Whilethe uptake of ⁴⁵Ca by 8/3 mS plants at night was similar tothat of 3 mS plants, the daily uptake was less than that in3 and 5.5 mS plants. The Ca content of tomato fruit increased with truss number at3 and 5.5 mS cm^–1 but not at 8/3 and 8 mS cm^–1.Within the same truss, the distal fruit had a lower Ca contentbut higher Mg content than the proximal fruit. The reductionin Ca content of the distal fruit at 8/3 mS cm^–1 was similarto that at 5.5 mS cm^–1. The Ca content of the tissue atthe distal end of the 8/3 mS fruit was lower than that of the5.5 mS fruit. Similarly, the distribution of ⁴⁵Ca to the distalhalf of the detached 8/3 mS fruit was less than that of 5.5mS fruit. A reduced uptake and inadequate distribution of Cato the truss and to the distal end of the 8/3 mS fruit werethe main causes of these differences. Lycopersicon esculentum(Mill.), tomato, fruit, calcium, magnesium, diurnal salinity     

Comparison of Effects of Potassium Iodide and Iodosalicylates on the Antioxidant Potential and Iodine Accumulation in Young Tomato Plants

Iodine (I) is classified as a beneficial element for plants. Until now, there have been only hypotheses regarding the uptakes of organic iodine compounds by plant roots. The purpose of our research was to compare the uptakes and effects of the application of the following mineral and organic iodine compounds on young tomato plants: KI, 5-iodosalicylic (5-ISA), and 3,5-diiodosalicylic (3,5-diISA) acids. An additional control combination included the treatment with salicylic acid (SA) alone. All compounds were introduced into the nutrient solution in 5, 10, 25, and 50 μM I concentrations. It was established that after the application of 5-ISA and 3,5-diISA, iodine is taken up to a smaller extent than from KI. The tested KI, 3,5-diISA, and 5-ISA doses had no negative impact on the growth and development of plants, apart from the reduction of shoot biomass after the application of 3,5-diISA in 10 and 25 µM I doses. All applied compounds, except for SA, caused a reduction of ascorbic acid (AA) content and increase of dehydroascorbic acid (DHA) content in leaves. A significant increase of APX activity was noted only for the highest doses of KI and 5-ISA. None of the iodine compounds, in most tested doses, have substantially increased the CAT and POX activities in tomato leaves. Application of KI decreased the levels of all analyzed sugars in tomato leaves. The effect of iodosalicylates on sugar content varied depending on the compound: when applied in the highest dose 5-ISA increased, while 3,5-diISA decreased the sugar accumulation in tomato plants. In all tested treatments, a reduction of SA content in leaves was noted. We conclude that organic iodine compounds, i.e., 3,5-diISA and 5-ISA, can be taken up by the roots of tomato plants at an early stage of development.

     

Growth and Nitrogen Accumulation in Young Tomato Plants Treated with Gibberellic Acid

The effects of foliar sprays of gibberellic acid (GA) on thegrowth of tomato plants cv. Potentate were studied in growthrooms and a glasshouse. Four sprays of GA (5 ppm) increasedleaf area and whole plant weight relative to water controlsgrown at constant temperatures (7, 17, 22, and 27 °C) for12 days, the largest plants being obtained with 5 ppm. Experimentsmade at four photoperiods (5, 10, 15, and 20 h) and at two lightintensities (7000 and 10 750 lx) showed that GA increased leafand whole plant weight at 15 h, leaf area at 10 and 15 h andstem height at all photoperiods; area, height, and weight increaseswere obtained at both light intensities, leaf growth being increasedmore by GA at 7000 lx and stem growth more at 10 750 lx. Four foliar sprays of GA (5 ppm) were combined with N supplementsapplied via leaf and/or root to plants in sand culture. Withlow supply to the roots (20 ppm N) GA failed to increase growth,but increased it at higher levels. Total N in leaf and stemwas increased by GA or by NH₄NO₃ (10 sprays 280 ppm N) at alllevels of N supplied to roots, but when applied together theeffect on total leaf N was more than additive except at thehighest level (540 ppm) GA increased the concentration of N(as per cent dry matter) in leaf and stem at all levels of Nsupplied to roots. GA and NH₄NO₃ together resulted in a greateramount and a higher concentration of N in the shoots (and usuallyalso in roots) than did NH₄NO₃ alone. Leaf thickness (as freshweight/unit area) could only be increased appreciably by sprayingwith a complete nutrient solution which reduced leaf area butnot dry weight. Growth increases induced by GA were detectable 43 days afterthe first of four sprays in the glasshouse and after 30 daysin the growth room. The persistence of GA effects was comparedwith those induced by sprays of NH₄NO₃.     

Effects of Osmotic Potential in Nutrient Solution on Diurnal Growth of Tomato Fruit

Tomato fruit on plants grown in circulating nutrient solutionexhibited a diurnal cycle in growth rate, measured as a changein diameter, with a maximum during thc day. The diurnal growthcycle was less evident in those fruit grown at high electricalconductivity (17 mS), or on days of reduced irradiance. Girdledfruit of low conductivity plants grew at a much reduced ratewith a diurnal cycle in reverse to that of ungirdled fruit,while girdled fruit of high conductivity plants showed no diurnalgrowth. The evidence suggests that phloem and xylem water transportinto fruit operate on opposite diurnal cycles. Partitioning of available xylem water in detached fruit betweenthe calyx and berry, as well as within the berry, was determinedby berry size and relative humidity in the air. Although berrytranspiration rate was unaffected by conductivity treatmentduring plant growth, water uptake capacity was greatly reducedin the berry from high conductivity plants, suggesting an increasedresistance in the xylem transport system within the fruit. Key words: Salinity, electrical conductivity, tomato fruit, xylem transport, transpiration     

Effects of Low-Molecular-Weight Organic Acids on Gadolinium Accumulation and Transportation in Tomato Plants

Effects of low-molecular-weight organic acids on the accumulation and transportation of gadolinium (Gd) in tomato plants were studied under hydroponic condition. The results indicated that changes of organic acids occurred in the processes of Gd accumulation and transportation in tomato plants which were treated with extraneous Gd solutions. Malic, citric, and succinic acids contributed to both Gd accumulation in roots and transportation in xylem vessels. When Gd was unloaded from the xylem to the leaf cells, formic, lactic, citric, and succinic acids played important roles in Gd accumulation in leaves. When tomato plants were cultured in the uptake solution of Gd-containing malic, citric, or succinic acid for 48 h, the succinic acid in roots and leaves and the malic acid in xylem saps both increased obviously. From the results above, we can conclude that succinic acid had the most important role in Gd accumulation in tomato roots and leaves, while malic acid transported Gd via xylem vessels more effectively.     

Effects of CO2-Enrichment on the Growth of Young Tomato Plants in Low Light

Carbon dioxide-enrichment of young tomato plants grown in controlled-environmentcabinets at low light intensity (14 cal cm^–2 day^–1,visible radiation) increased their net assimilation rates and,initially, relative growth-rates. Subsequently, the relativegrowth-rate fell to near the rate of non-enriched plants, owingto a fall in leaf-area ratio associated with an increase inleaf dry weight/area. Sowing non-enriched plants a few daysearlier to reach the same total dry weight would not have producedidentical plants. The effects of CO₂-enrichment to 1000 vpm could be simulatedby increasing light intensity by approximately one third exceptthat the plants had shorter internodes than those in extra CO₂.This was a morphogenetic effect of light since CO₂-enrichmentitself produced slightly shorter plants than controls for anequivalent total dry weight. CO₂-enrichment did not change the dry-weight distribution inthe plants and had little effect on rate of leaf produoctionor the number of flower primordia. There were no indicationsthat beneficial effects of CO₂-enrichment operated other thanthrough increased photosynthesis.     

Pathways of Uptake and Accumulation of Sugars in Tomato Fruit

The route of sucrose unloading from the conducting tissue, theregulation of sucrose hydrolysis and the uptake and subsequentmetabolism of sugars were investigated in the rapidly growingtomato fruit. During the first two weeks of fruit enlargement, the vacuoleaccounted for more than 85% of the protoplast volume and theintercellular space accounted for 20% of the fruit placentaltissue. The plasmodesmatal frequency was highest between phloemparenchyma cells and lowest between phloem sieve cells and phloemparenchyma. The total invertase activity was about 8 µmolglucose g^–1 d. wt min^–1 during the rapid growingperiod and increased six-fold at ripening. The wall-bound invertaseaccounted for less than 11% of the total activity. Invertaseactivity increased with increasing sucrose concentrations (upto 50 mM) in the incubation medium, but decreased at higherconcentrations. Sucrose synthase activity could only be detectedwhen fruit was older than 19 d. The uptake and metabolism of sugars by fruit cells were investigatedby incubation of fruit slices with ¹⁴C-sugars for 3 h. The uptakeof sucrose increased with the sucrose concentration up to 200mM. The rate of glucose uptake and its conversion to the ethanol-insolublefraction were higher than those of sucrose. The uptake of sucrosedid not compete with that of glucose or vice versa, providedthe osmotic potential of the incubation solution was maintainedconstant. The uptake of sucrose was not inhibited by metabolicinhibitors such as PCMBS, CCCP, sodium azide or vanadate. TheATPase activity in the fruit tissue was low. These findings did not identify conclusively the mode of sucroseunloading. However, the uptake of sugars by fruit cells is non-specificand does not appear to require a membrane carrier or plasmalemmaATPase to provide energy for sucrose uptake. Fruit, invertase, Lycopersicon esculentum, phloem unloading, plasmodesmata, sucrose     

花期减少施钙量对不同钙效率番茄果实钙形态和含量的影响

花期降低施钙量后,钙低效番茄品种L-402果实中钙含量显著降低,高效品种江蔬一号降低不显著,镁含量显著增加,钾含量有增加趋势。果实底端的钙含量高于顶端,降低施钙量后果实水溶性钙含量和比例显著提高,果胶酸钙含量和比例降低,磷酸钙含量也降低。钙低效品种L-402水溶性钙含量的增加,以及果胶酸钙和磷酸钙的降低程度,都大于高效品种江蔬一号,且降钙后果实顶端的革酸钙含量和比例增加。     

Sucrose Synthase,Starch Accumulation,and Tomato Fruit Sink Strength

Contrasting evidence has accumulated regarding the role of acid invertase and sucrose synthase in tomato fruit sink establishment and maintenance. In this work the relationships among the activities of sucrose synthase and acid invertase, Lycopersicon esculentum Mill cv UC-82B fruit growth, and starch accumulation were analyzed in fruit at 0 to 39 d after anthesis. Sucrose synthase, but not acid invertase, was found to be positively correlated with tomato fruit relative growth rate and with starch content in the pericarp tissue. A similar association between sucrose synthase activity and starch accumulation was also evident in the basal portion of the stem. Heat-shock treatments, which inhibited the increase in sucrose synthase activity at the beginning of the light period and had no effect on acid invertase activity, were used to examine the importance of sucrose synthase in relation to sucrose metabolism and starch synthesis. After the heat-shock treatment, concomitantly with the suppressed sucrose synthase activity relative to the controls, there was a reduction in sucrose cleavage and starch accumulation. These data substantiate the conclusion that, during the early phases of tomato fruit development, sucrose synthase rather than acid invertase is the dominant enzyme in metabolizing imported sucrose, which in turn plays a part in regulating the import of sucrose into the fruit.     

Drought- and ABA-Induced Changes in Polypeptide and mRNA Accumulation in Tomato Leaves

Drought stress triggers abscisic acid (ABA) biosynthesis resulting in ABA accumulation. The ABA-deficient tomato mutant, flacca (Lycopersicon esculentum Mill. cv Ailsa Craig), does not synthesize ABA in response to drought stress. This mutant has been used to distinguish polypeptides and in vitro translation products that are synthesized during drought stress in response to elevated ABA levels from those that are induced directly by altered water relations. A set of polypeptides and in vitro translation products was synthesized during drought stress in the wild type. These polypeptides and in vitro translation products were synthesized to a lesser extent in the drought-stressed ABA-deficient mutant. Treatment of flacca with ABA resulted in the synthesis of the drought-stress-induced polypeptides and in vitro translation products. These results support the hypothesis that many of the polypeptides that are synthesized during drought are regulated by alterations in ABA concentration. Similarly, the mRNA population was altered by ABA during drought stress.     

Reversible Inhibition of Tomato Fruit Gene Expression at High Temperature (Effects on Tomato Fruit Ripening)

The reversible inhibition of three ripening-related processes by high-temperature treatment (38[deg]C) was examined in tomato (Lycopersicon esculentum L. cv Daniella) fruit. Ethylene production, color development, and softening were inhibited during heating and recovered afterward, whether recovery took place at 20[deg]C or fruit were first held at chilling temperature (2[deg]C) after heating and then placed at 20[deg]C. Ethylene production and color development proceeded normally in heated fruit after 14 d of chilling, whereas the unheated fruit had delayed ethylene production and uneven color development. Levels of mRNA for 1-aminocyclopropane-1-carboxylic acid oxidase, phytoene synthase, and polygalacturonase decreased dramatically during the heat treatment but recovered afterward, whereas the mRNA for HSP17 increased during the high-temperature treatment and then decreased when fruit were removed from heat. As monitored by western blots, the HSP17 protein disappeared from fruit tissue after 3 d at 20[deg]C but remained when fruit were held at 2[deg]C. The persistence of heat-shock proteins at low temperature may be relevant to the protection against chilling injury provided by the heat treatment. Protein levels of 1-aminocyclopropane-1-carboxylic acid oxidase and polygalacturonase also did not closely follow the changes in their respective mRNAs. This implied both differences in relative stability and turnover rates of mRNA compared to protein and nontranslation of the message that accumulated in low temperature. The results suggest that high temperature inhibits ripening by inhibiting the accumulation of ripening-related mRNAs. Ripening processes that depend on continuous protein synthesis including ethylene production, lycopene accumulation, and cell-wall dissolution are thereby diminished.     

Effects of Waterlogging on the Gibberellin Content and Growth of Tomato Plants

Flooding of tomato roots results in decreased stem growth. Wehave shown that flooding will reduce levels of gibberellins(GA) in the roots, shoots, and bleeding sap of tomato plants.The adventitious roots that appear on the third day of waterloggingmay be responsible for the production of GA that accumulatein the shoot after 3 to 4 days of flooding. The endogenous GAof tomato will stimulate stem growth of tomato plants. Initially,application of gibberellic acid (GA₃) will stimulate the growthof flooded plants to a greater extent than that of nonwaterloggedplants. It is suggested that one of the first effects of floodingis to reduce GA levels and so inhibit stem elongation. At alater stage of waterlogging GA₃ is less effective and otherfactors appear to inhibit shoot growth.     

Effects of Heat Stress on Carbon Transport from Tomato Leaves

Export of radioactive carbon from two cultivars of tomato, (Lycopersiconesculentum Mill.) leaves was inhibited in response to heat stress.Increasing temperatures resulted in a marked decrease in leafstarch levels. The depletion of starch concentration in theleaves was primarily due to hydrolysis and an inhibition ofstarch formation. At high temperatures, starch hydrolysis wasinhibited in Roma VF, a heat sensitive cultivar, while Saladette,a heat tolerant cultivar was not similarly affected. Calloseformation was found on phloem sieve tube plates of leaf petiolesexposed to 72 h of high temperatures. More sieve tube plateswere covered with a thicker callose layer in Roma VF than inSaladette. Lycopersicon esculentum (Mill.), tomato, carbon translocation, starch hydrolysis, callose, heat stress     

番茄黄化曲叶病毒对番茄叶片光合特性和叶绿体超微结构的影响

以番茄为试验材料,研究番茄黄化曲叶病毒(TYLCV)侵染对植株叶片叶绿素含量、净光合速率、气孔导度、胞间CO2浓度和叶绿体超微结构的影响.结果表明:TYLCV侵染番茄后,叶片叶绿素a、b以及总叶绿素含量分别下降50.2%、24.19%和43.84%,叶片净光合速率和气孔导度分别下降43.28%、27.07%,胞间CO2浓度增加13.04%.与健康叶片相比,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离,质壁分离和细胞膜内陷,细胞器消解.研究表明,TYLCV侵染破坏了番茄叶片的叶绿体结构,严重影响番茄叶片的光合作用.     

Effects of Water Deficit on Phosphorus Nutrition of Tomato Plants

Measurements were made of phosphorus uptake by intact tomato plants from solutions labelled with ³²P. The plants were exposed to low water potentials by the addition of mannitol to culture solutions. The amounts of labelled phosphorus in the roots and in the shoots wore determined after a one- or two-hour period. Down to -5.4 atmospheres, the amount of labelled phosphorus in the roots remained constant, hut the amount transported to the shoots was reduced. However, potentials of -10.4 atm reduced the amount of labelled phosphorus in both the root and the shoot. Similar results were obtained when plants were tested immediately after water stress was imposed and when tested after water potentials had been lowered gradually. Plants were treated for one hour at low water potentials and then returned to control solutions (?0.4 atm). For a considerable time, these plants had a much lower phosphorus uptake than plants which had remained continuously at ?0.4 atm. These data support the idea that a disturbance in mineral nutrition is partly responsible for reduced growth in plants which experience a moderate water deficit.     

Effects of Salinity, Diurnal Cycle and Age on Nucleotide Pools of Bean Leaves

In the present study, we investigated the relationship betweensalt stress and nucleotide levels in the shoot of Phaseolusvulgaris L. cv. Stringless Green Pod to determine if reducedgrowth was correlated with reduced nucleotide levels. Overallfresh weight of 25-d-old plants after having been on full salttreatment for 7 d was 33% lower compared with untreated plants.Shoot fresh weight decreased by 40% compared with 22% for theroots thus increasing the root to shoot ratio from 0·7to 0·9. We examined young and juvenile leaves as wellas mature leaves in order to compare growing tissue to fullyenlarged tissue. To ascertain whether the effects of salt stresson nucleotide pools were more severe during the day than atnight, we studied the combined effects of diurnal cycle andsalt stress on these nucleotide pools. Salt treatment selectivelyaffected certain nucleotide pools with the adenine nucleotides(AdN) being the most affected. We found large diurnal fluctuationsof AdN pools in all leaves. During the day, AMP and ADP increasedwhile ATP decreased. The sum, ATP + ADP, tended to remain constantand in mature leaves total AdN increased with AMP, an indicationof net synthesis. At night, ATP increased in all leaves. However,salt stress prevented this night-time increase in mature leaveswhile enhancing it in juvenile and young leaves. In the daytime,salt stress caused a nearly 2-fold increase in AMP of youngleaves and a large increase in the adenylate kinase mass actionratio (K). At night, the excess AMP disappeared with no changein total AdN. It is clear from these results that salt stressdid not reduce shoot growth by depleting ATP in growing leaves.It did, however, reduce the ATP level of mature leaves and perhapstheir ability to supply essential metabolites for growing regions. Key words: Phaseolus, nucleotides, salt stress, salinity, growth     

Hormone Effects on the Membrane Potential and on Sucrose-Induced Depolarization of Young Citrus Leaves

The effect of IAA, GA₃ and ABA on transmembrane potential difference(Em) and on sucrose-induced depolarization has been studiedin young Citrus leaves. The addition of any of these hormonesto the perfusion solution (short-term experiments) did not affectEm or sucrose-induced depolarization. Hormonal treatments ofyoung leaves on the tree resulted, after 4 to 16 days (long-termexperiments), in an increase of Em for GA₃- and ABA-treatedleaves, while in IAA-treated ones no hyperpolarization was found.Only in ABA treated leaves this membrane hyperpolarization couldbe related to an enhancement of sucrose uptake. (Received April 28, 1992; Accepted September 21, 1992)