The effect of assimilate supply on fruit growth and hormone levels in tomato plants

Rates of dry matter accumulation and contents of starch, sugars and abscisic acid (ABA) of tomato fruits differed significantly during development at three positions (proximal, middle and distal) on a truss. Proximal fruits, which accumulated dry matter most rapidly during early development, generally had least ABA (per g DW).Partial defoliation reduced carbon accumulation by all fruits but increased ABA, especially in distal fruit, and indoleacetic acid (IAA), particularly in proximal fruits. The ABA content of leaves in partially defoliated plants was similar to that of leaves on non-defoliated plants.Removal of distal fruits on a truss enhanced carbon movement to the remaining proximal fruits and also increased their ABA content early in development but did not affect their IAA content. On the other hand, when proximal fruit were removed there was no large or lasting increased accumulation of carbon by the remaining distal fruits and they contained less ABA and IAA than fruits on plants without fruit thinning. Leaf carbon and ABA levels showed no marked trend in response to fruit thinning.The amount of carbon in the stems was increased by fruit thinning but decreased by partial defoliation.The possible roles of ABA and IAA in regulating fruit growth are discussed.Part of this work has been presented to a Symposium on Phloem loading and related processes at Bad Grund/Oberhar, W. Germany, July 1979.     

The effect of iron ethylenediaminetetraacetic acid on the growth and metabolism of tomato plants in water culture

Summary Tomato plants were grown in nutrient culture either continuously or discontinuously treated with FeSO₄ or with Fe-EDTA. FeSO₄ rapidly gave a precipitate of Fe₂O₃.nH₂O but remained, under the conditions of the experiments, available to the plants. Fe absorbed from Fe-EDTA in the nutrient medium was less effective in inducing tomato plant growth than iron supplied as ferrous sulphate. This cannot be explained in terms of luxury consumption or by phosphate-induced internal iron immobilization.Plants grown continuously with Fe-EDTA as an iron source showed consistently higher peroxidase and catalase activities. Chlorotic plants treated for a few days with FeSO₄ exhibited mostly equal or higher enzyme activities than those treated with Fe-EDTA. The ratio of green and yellow chloroplast pigments was constant under all the tested levels of iron nutrition.Although there were significant differences in iron utilization, enzyme activities, and some symptoms of slightly modified growth, the main conclusion of this investigation is that, under these strictly comparable conditions, plant metabolism has not been modified considerably by the use of the synthetic iron chelates.     

Effect of seaweed concentrate on the establishment and yield of greenhouse tomato plants

Seaweed concentrate prepared fromEcklonia maxima (Osbeck) Papenfuss, when applied as a soil drench, significantly improved the growth of tomato seedlings. Application as a foliar spray had no effect on young plants. In a second experiment SWC-treated plants exhibited early fruit ripening and a total fruit fresh weight increase of 17%. The number of harvested fruit were improved by about 10%. In this instance foliar applied SWC was more beneficial than SWC applied to the soil. The significance of these findings is discussed.author for correspondence     

Metabolic responses in iron deficient tomato plants

The effects of Fe deficiency on different metabolic processes were characterized in roots, xylem sap and leaves of tomato. The total organic acid pool increased significantly with Fe deficiency in xylem sap and leaves of tomato plants, whereas it did not change in roots. However, the composition of the pool changed with Fe deficiency, with major increases in citrate concentrations in roots (20-fold), leaves (2-fold) and xylem sap (17-fold). The activity of phosphoenolpyruvate carboxylase, an enzyme leading to anaplerotic C fixation, increased 10-fold in root tip extracts with Fe deficiency, whereas no change was observed in leaf extracts. The activities of the organic acid synthesis-related enzymes malate dehydrogenase, citrate synthase, isocitrate dehydrogenase, fumarase and aconitase, as well as those of the enzymes lactate dehydrogenase and pyruvate carboxylase, increased with Fe deficiency in root extracts, whereas only citrate synthase increased significantly with Fe deficiency in leaf extracts. These results suggest that the enhanced C fixation capacity in Fe-deficient tomato roots may result in producing citrate that could be used for Fe xylem transport. Total pyridine nucleotide pools did not change significantly with Fe deficiency in roots or leaves, although NAD(P)H/NAD(P) ratios were lower in Fe-deficient roots than in controls. Rates of O(2) consumption were similar in Fe-deficient and Fe-sufficient roots, but the capacity of the alternative oxidase pathway was decreased by Fe deficiency. Also, increases in Fe reductase activity with Fe deficiency were only 2-fold higher when measured in tomato root tips. These values are significantly lower than those found in other plant species, where Fe deficiency leads to larger increases in organic acid synthesis-related enzyme activities and flavin accumulation. These data support the hypothesis that the extent of activation of different metabolic pathways, including carbon fixation via PEPC, organic acid synthesis-related enzymes and oxygen consumption is different among species, and this could modulate the different levels of efficiency in Strategy I plants.     

The effect of growth substances on Verticillium wilt of tomato plants

This paper describes the effects of a number of growth-regulating substances on the development of disease in tomato plants caused by Verticillium albo-atrum. Indole-acetic acid usually reduced disease and also reduced the number of hyphae in the stem but it increased tylosis; low concentrations slightly stimulated disease development. Some control of disease was obtained by removing apical buds, and axillary shoots as they developed. When the apical bud alone was removed, developing axillary shoots sometimes wilted; this did not occur in plants with intact buds. Gibberellic acid increased disease in susceptible plants and also induced symptoms in resistant plants. Maleic hydrazide greatly reduced growth of plants, made them more diseased and stimulated growth of the parasite in the vessels. Of other growth-regulating substances tested, 2,4,6-trichlorophenoxy-acetic acid, 2,3,5-triiodobenzoic acid and 2,4-dichlorophenoxyacetic acid increased disease at some concentrations and reduced it at others. Cycocel (2-chloroethyl) trimethyl ammonium chloride and naphthaleneacetamide, gave good control of disease over a range of concentrations when applied to the soil in which plants were growing. Treatments which reduced disease also reduced the growth of the parasite in the shoot and stimulated the formation of tyloses. Indole and 2,4-dichloroanisole had some effect on disease development but this was much less than that induced by the other substances.     

The effect of cadmium on lipid and fatty acid biosynthesis in tomato leaves

This research aims to examine the effect of cadmium uptake on lipid composition and fatty acid biosynthesis, in young leaves of tomato treated seedlings (Lycopersicon esculentum cv. Ibiza F1). Results in membrane lipids investigations revealed that high cadmium concentrations affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the unsaturated fatty acid content, resulting in a lower degree of fatty acid unsaturation. The level of lipid peroxides was significantly enhanced at high Cd concentrations. Studies of the lipid metabolism using radioactive labelling with [1-¹⁴C]acetate as a major precursor of lipid biosynthesis, showed that levels of radioactivity incorporation in total lipids as well as in all lipid classes were lowered by Cd doses. In total lipid fatty acids, [1-¹⁴C]acetate incorporation was reduced in tri-unsaturated fatty acids (C16:3 and C18:3); While it was enhanced in the palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0) and linoleic (C18:2) acids. [1-¹⁴C]acetate incorporation into C16:3 and C18:3 of galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] and some phospholipids [phosphatidylcholine (PC) and phosphatidylglycerol (PG)] was inhibited by Cd stress. Our results showed that in tomato plants, cadmium stress provoked an inhibition of polar lipid biosynthesis and reduced fatty acid desaturation process.     

Isolation and properties of carboxypeptidase from leaves of wounded tomato plants

A carboxypeptidase was purified to homogeneity from upper, unwounded leaves of tomato plants in which carboxypeptidase activity had been induced to increase over three-fold by severely wounding the lower leaves. The carboxypeptidase was purified by ammonium sulfate precipitation, affinity chromatography, and finally by gel permeation chromatography. Electrophoresis at pH 4.3 and isoelectric focusing showed only a single band. The isoelectric point was 5.2 and the MW 105 000. Tomato carboxypeptidase possessed both peptidase and esterase activities and it sequentially hydrolysed amino acids from the carboxyl-terminal end of insulin chain B. It was optimally active at pH 6–7 on peptidase substrates, and at pH 8 on esterase substrates. The enzyme was inhibited by diisopropylfluorophosphate and incorporated 1 mol of DFP-[³H]. per mol of enzyme. Both peptidase and esterase activities were strongly inhibited by HgCl₂ but not by p-hydroxymercuribenzoate or iodoacetamide. Carboxypeptidase inhibitor from potatoes did not inhibit the enzyme.     

Interactive effects of salinity and nitrogen on growth and yield of tomato plants

Summary Tomato (Lycopersicon esculentum var. VF 145) plants were grown with Typic Xerofluvents soil in a greenhouse irrigated with recycled nutrient solutions having increasing levels of N and salinity. Positive response of plants to increasing levels of N was obtained at the lowest initial salinity level of 1 dS/m (dS/m=mmho/cm, referenced at 25°C). At the higher initial salinity levels of 5 and 9 dS/m, increasing N was ineffective in counteracting adverse effects on growth and yield caused by the presence of enhanced salt concentrations of the nutrient solution. Total N uptake was linearly correlated with the total water uptake and was severely suppressed by impaired growth associated with the two higher initial salinity levels, irrespective of N levels. The effect of salinity on leaf N concentrations changed over time. Leaf Cl and P concentrations indicated a possible suppressing effect of Cl on P uptake into plant tops.Based on portions of the thesis submitted by the senior author in partial satisfaction of the requirements for the Ph.D. degree in Soil Science. Supported in part by a grant from the Kearney Foundation of Soil Science.     

The influence of the chemical composition of a nutrient solution on the production of tomato plants

Summary The influence of 12 combinations of 5 different relative anion ratios and 3 different relative cation ratios in a nutrient solution on the production of tomato plants has been investigated in gravel culture during the years 1962, 1963 and 1964.There were 5 N levels, respectively 36.3%, 54.4%, 63.1%, 72.5% and 86.0% of the total anions in equivalents and 3 K levels, respectively 66.8%, 33.7% and 22.4% of the total cations in equivalents.Although differences were small, there was a significant reduction of earliness and total production for the highest N level. The other N levels showed no difference.Earliness and total production were significantly better with the lower K levels, but again differences were small.The influence of the composition of the nutrient solution on the production of the tomato plant was shown to be very small.     

Antioxidative response to cadmium in roots and leaves of tomato plants

Treatment of tomato seedlings (Lycopersicon esculentum Mill. cv. 63/5 F1) with increasing CdCl₂ concentrations in the culture medium resulted in Cd accumulation more important in roots than in leaves. Biomass production was severely inhibited, even at low Cd concentration. Cd reduced chlorophyll content in leaves and enhanced lipid peroxidation. An increase in antioxidative enzyme (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase) activities was more pronounced in leaves than in roots, while catalase activity increased only in roots. In addition, changes in isoenzyme composition were observed using the non-denaturing polyacrylamid gel electrophoresis.     

Some effects of varied calcium nutrition on the growth and composition of tomato plants

Summary Tomato plants were grown in nutrient solutions containing 0.05, 0.2, 1.0, 5.0, 15.0 and 30.0 meq Ca/l. Plants grown at the lowest level of calcium suffered from calcium deficiency and produced the least amount of dry matter. Dry matter yield was optimal from plants grown in the solution containing only 0.2 meq Ca/l and decreased at higher levels of substrate calcium. Despite large differences in the concentrations of the individual ions in the dried material, highly significant (P < 0.001) relationships were found between total cations and total anions and between insoluble calcium and oxalate.An explanation for the observed response to calcium is suggested based on the stimulation of the synthesis of oxalate by tissue calcium at the expense of carbohydrates. re]19760812     

Pre-sowing magnetic treatments of tomato seeds increase the growth and yield of plants

The effects of pre-sowing magnetic treatments on growth and yield of tomato (cv Campbell-28) were investigated under field conditions. Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 100 mT (rms) for 10 min and at 170 mT (rms) for 3 min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (30.2 m(2)) and were cultivated according to standard agricultural practices. During the vegetative and generative growth stages, samples were collected at regular intervals for growth rate analyses, and the resistance of plants to geminivirus and early blight was evaluated. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters were determined. In the vegetative stage, the treatments led to a significant increase in leaf area, leaf dry weight, and specific leaf area (SLA) per plant. Also, the leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. In the generative stage, leaf area per plant and relative growth rates of fruits from plants from magnetically exposed seeds were greater than those of the control plant fruits. At fruit maturity stage, all magnetic treatments increased significantly (P < .05) the mean fruit weight, the fruit yield per plant, the fruit yield per area, and the equatorial diameter of fruits in comparison with the controls. At the end of the experiment, total dry matter was significantly higher for plants from magnetically treated seeds than that of the controls. A significant delay in the appearance of first symptoms of geminivirus and early blight and a reduced infection rate of early blight were observed in the plants from exposed seeds to MFs. Pre-sowing magnetic treatments would enhance the growth and yield of tomato crop.     

The effect of Botrytis cinerea infection on the antioxidant profile of mitochondria from tomato leaves

Infection of tomato leaves with the necrotrophic fungus Botrytis cinerea resulted in substantial changes in enzymatic and non-enzymatic components of the ascorbate-glutathione cycle as well as in superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione transferase (GST), and l-galactono-gamma-lactone dehydrogenase (GLDH) activities. In the initial phase of the 5 d experiment CuZn SOD was the most rapidly induced isoform (up to 209% of control), whereas later on its activity increase was not concomitant with the constant total SOD enhancement. Starting from the second day B. cinerea infection diminished the mitochondrial antioxidant capacity by decreasing activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) as well as declining ascorbate and glutathione contents. This was accompanied by dehydroascorbate (DHA) and oxidized glutathione (GSSG) accumulation that resulted in ascorbate and glutathione redox ratios decreases. The strongest redox ratio decline of 29% for ascorbate and of 34% for glutathione was found on the 3rd and 2nd days, respectively. Glutathione reductase (GR) induction (185% of control 2 d after inoculation) was insufficient to overcome the decreased antioxidant potential of glutathione. Changes in the ascorbate pool size were closely related to the activity of l-galactono-gamma-lactone dehydrogenase (GLDH). The activities of two glutathione-dependent enzymes: GSH-Px and GST were increased from day 1 to day 4. These results demonstrated that in B. cinerea-tomato interaction mitochondria could be one of the main targets for infection-induced oxidative stress.     

Growth and photosynthesis of pea plants under different iron supply

Soil conditions, leading to iron deficiency or toxicity, are widespread in nature. Our objective was to study the effect of Fe supply, ranging from complete deficiency to excess, on growth and on some photosynthetic indices of pea plants. Both iron deficiency and toxicity decreased shoot and root growth. Complete deficiency resulted in a lower shoot/root ratio and a higher content of dry biomass per unit of fresh biomass in roots, while iron excess led to higher content of dry biomass per unit of fresh biomass in shoot. Complete deficiency was also characterized by low chlorophyll and carotenoid content, elevated ratios of chlorophyll a/chlorophyll b and carotenoids/chlorophylls, a drop of photosynthetic rate per leaf area, and an increase of photosynthetic rate per chlorophyll. The stomatal resistance substantially increased, while the transpiration rate decreased. Smaller changes in stomatal resistance and transpiration rate, but not in photosynthetic rate per leaf area, were found under partial iron deficiency and under excess of iron. In the first case, the chlorophyll content decreased, while in the second it increased. The maximum efficiency of photosystem II was unaffected by iron supply. Even when no genetic or experimental differences existed, changes in growth, pigment content and photosynthesis due to variation of Fe supply depended on the type and severity of the imposed stress, as well as on the studied parameter. A combination of indices described better the effect of iron supply, especially when small differences were characterized.     

The effect of competition from neighbours on stomatal conductance in lettuce and tomato plants

Competition decreased transpiration from young lettuce plants after 2 days, before any reductions in leaf area became apparent, and stomatal conductance (g(s) ) of lettuce and tomato plants was also reduced. Stomatal closure was not due to hydraulic signals or competition for nutrients, as soil water content, leaf water status and leaf nitrate concentrations were unaffected by neighbours. Competition-induced stomatal closure was absent in an abscisic acid (ABA)-deficient tomato mutant, flacca, indicating a fundamental involvement of ABA. Although tomato xylem sap ABA concentrations were unaffected by the presence of neighbours, ABA/pH-based stomatal modulation is still likely to underlie the response to competition, as soil and xylem sap alkalization was observed in competing plants. Competition also modulated leaf ethylene production, and treatment of lettuce plants with an ethylene perception inhibitor (1-methylcyclopropene) diminished the difference in g(s) between single and competing plants grown in a controlled environment room, but increased it in plants grown in the greenhouse: ethylene altered the extent of the stomatal response to competition. Effects of competition on g(s) are discussed in terms of the detection of the absence of neighbours: increases in g(s) and carbon fixation may allow faster initial space occupancy within an emerging community/crop.