Search Results
Abstract
A single spraying of 2-chloro-9-hydroxyfluorene-9-carboxylic acid (chlorflurenol) on the foliage increased the set rate of processing tomatoes under conditions of high temperature as compared with untreated control or 4-CPA-treated plants. As the rate applied increased, chlorflurenol inhibited vegetative growth, increased fruit malformation, and decreased the pH of fruit juice (0.1 unit). No differences could be detected in juice viscosity and in total soluble solids of treated and control fruits.
Abstract
Green tomato fruits were treated with 2-(4-chlorophenylthio) triethylamino hydrochloride (CPTA) and/or (2-choroethyl)phosphonic acid (ethephon) and were stored for 10 days at a temperature of 32°C. CPTA-treated fruits developed red color mostly in the exocarp, while ethephon and no n-treated fruits showed yellow coloring. The combined effect of CPTA and ethephon on red color development was stronger than that of CPTA alone. As lycopene normally does not develop at high temperature it seems likely mat CPTA acts in a pathway different from the normal.
Abstract
Effects of growth regulators on parthenocarpic fruit development in muskmelon (Cucumis melo L.) were tested under field conditions. Parachlorophenoxyacetic acid (4-CPA) β-naphtoxyacetic acid (β-NOA), gibberellin (GA4+7), and 2-chloro-9-hydroxyfluorene-9-carboxylic acid (chlorflurenol) caused parthenocarpy, when applied directly to flowers at anthesis. Seed coat developed in all parthenocarpic fruits. A positive correlation (r = 0.80) was found between number of seeds, seed coats, and fruit weight. Fruit set was induced under field conditions without bees, by a single spray of 4-CPA or β-NOA or chlorflurenol applied to the entire plant.
Salt tolerance of 59 cultigens of tomato (Lycopersicon esculentum Mill.), seven wild Lycopersicon accessions (acc.), and one interspecific hybrid was studied under arid field conditions. Evaluation of salt tolerance was based on relative total dry matter (RD) and relative total yield (RY), calculated as the ratio between performances of salinetreated and control plants. The tomato cultigens were irrigated with water having electrical conductivities (ECi) of 1.5 (control), 5, 10, or 15 dS·m−1. Considerable variation in salt tolerance was found among the cultigens, but at 15 dS·m−1 all showed reduced RD and RY (<0.6). The cultivar M82-1-8 (M82), one accession of L. cheesmanii (Lc), three accessions of L. pennellii (Lpen), three of L. peruvianum (Lper), and an interspecific F1 hybrid (M82 × Lpen acc. LA-716) were examined for RD at three salinity levels, ECi = 1.5, 10, and 20 dS·m−1, in three annual trials. The salt tolerance of Lpen and Lper were higher than those of M82 and Lc; the interspecific F1 was the most tolerant and was usually unaffected by even the highest salinity level. The results of this study indicate the existence of a genetic potential for high salt tolerance in wild Lycopersicon germplasm.
Accessions of four tomato species, Lycopersicon esculentum Mill. (Le), L. pennellii (Corr.) O'Arey (Lpen), L. cheesmanii Riley (Lc), and L. peruvianum (L.) Mill., (Lper), and interspecific populations were irrigated with saline water under field conditions and concentrations of Na, K, Cl, Ca, and Mg in leaves and stems were determined. Potassium: sodium ratios in leaves and stems of salt-tolerant genotypes were higher under salinity and were moderately changed by salinity compared to the sensitive genotypes. In the tolerant wild accessions and F1(Le × Lpen), Cl concentrations in leaves and the ratio between Cl in leaves to Cl in stems were lower than in the sensitive Le cultivar. Regulation of the K: Na ratio was found in tolerant wild accessions and tolerant Le cultivars, while regulation of Cl concentration in leaves was found only in the wild germplasm. The effects of ion concentrations on dry matter of interspecific segregating populations, F2(Le × Lpen) and BC1(Le × (Le × Lpen)), were studied by regression analyses. Dry matter was positively correlated with the K: Na ratio in stems and negatively correlated with the Cl concentrations in leaves and stems, thus confirming the results obtained by comparison between the tolerant and sensitive accessions.
Abstract
A computer program was developed for predicting the times of emergence, flowering, turning stage, and harvesting of processing tomatoes. The program was validated and calibrated by using 1972-1980 tomato data from 44 fields at 2 locations in Israel. Predictions are based on accumulation of heat units defined in terms of “physiological days”, where 1 physiological day is equivalent to a calendar day with a constant temperature of 26°C. The growing season was divided into 4 stages: from sowing to emergence, from emergence to flowering, from flowering to turning stage, and from turning stage to harvesting. Accumulation of physiological days during the first 2 stages is based on a linear function. During the last 2 stages, a quadratic function is used to calculate daytime heat units wherever the daily average temperature is above 20°. The maximum rate of development is at 26°. In the last stage, soil stress index also is taken into account. Use of the model makes it possible to predict the day of harvest with a precision of ±3 days, as compared with ±9 days when a daily mean systems is employed.
Abstract
The effect of temperature on CO2 fixation was studied in 2 tomato (Lycopersicon esculentum Mill.) cultivars; the heat-sensitive “Roma VF” and the heat-tolerant “Saladette". A decrease in apparent photosynthesis was found in both cultivars after plant exposure for various lengths of time to temperatures of 35° to 40°C. An increase in temperature also increased transpiration and raised the CO2 compensation point. The decrease in photosynthesis after a short exposure to high temperature was due to an increase in mesophyll resistance and, to a lesser extent, to an increase in stomatal resistance to CO2 diffusion. Saladette was less affected by high temperature and had a slightly greater photosynthetic capacity than the heat-sensitive Roma VF, after pretreatment at high temperature.
Abstract
The interaction of the gibberellins GA3 and GA4+7 with SADH on growth and sex expression was tested on andromonoecious muskmelon (Cucumis melo L. cv. Ananas PMR). SADH effectively reduced internode length and increased female tendency of plants. GA4+7 had an opposite effect on both growth and sex expression. GA3 was much less effective in both respects. The growth regulators were mutually antagonistic when plants were treated with both GA and SADH. The endogenous level of gibberellin decreased in SADH-treated plants 2 and 7 days after treatment. Gibberellin content reached the level of untreated plants 2 weeks after treatment, some time before the growth retarding effect of SADH treatment disappeared. These results indicate that the effect of its effect on the endogenous levels of gibberellin.
Abstract
The effect of growth regulators indoleacetic acid (IAA), parachlorophenoxy-acetic acid (4-CPA), β-napthoxyacetic acid (β-NOA), gibberellin (GA3 and GA4+7) and benzyladenine (BA) applied directly to flowers at anthesis, caused parthenocarpy in cucumbers (Cucumis sativus L.), while (2 chloroethyl)phosphonic acid (ethephon) and abscisic acid (ABA) were ineffective. Only synthetic auxins and BA effectively induced parthenocarpy in treated whole plants. 4-CPA was the most effective treatment for induction of parthenocarpic fruits, as determined by number and shape. Application of GA to the entire plant caused increase in vegetative growth, but fruit development was inhibited even under conditions of natural pollination.
Abstract
Accessions of several wild tomato species [Lycopersicon hirsutum H. and B. (LA 1363 and LA 1777), L. chilense Dun. (LA 1969 and LA 1971), and Solanum lycopersicoides Dun. (LA 1964)] were examined for cold tolerance and compared to the fast germination of L. esculentum Mill. PI 341988 and to the normal germination of ‘UC82B’. The wild accessions were collected above 3000 m and presumed to be cold-tolerant because of natural habitat. A number of characteristics, including germination, emergence, chlorophyll fluorescence, electrolyte leakage, and plastochron index were used to evaluate chilling resistance. PI 341988 germinated faster than the other genotypes at temperatures above 10°C, but germination of this accession virtually ceased below 10°. The high-altitude accessions continued to germinate, albeit at a reduced rate, below 10°. Growth rates at 12°/6° (day/night) were compared to growth at 24°/18° and were found to be greater in the high-altitude accessions than ‘UC82B’ The reduction in chlorophyll fluorescence when leaf disks were exposed to 1° was less in the high-altitude accessions than in ‘UC82B’, indicating less effect of this temperature on photosynthesis in the wild species. Electrolyte leakage was greater in ‘UC82B’ and LA1777 (L. hirsutum) than high-altitude accessions of L. chilense and S. lycopersicoides, but evidence is presented that this method is not reliable in screening for cold tolerance. Crosses were made between ‘UC82B’ and the wild species, and segregating populations were screened using the methods mentioned above. In each population, there were plants that showed cold resistance similar to the wild parent, suggesting the possibility of developing cold-tolerant cultivars.