Mary M. Peet

Formation of parthenocarpic fruit, undeveloped flowers and aborted flowers in tomato under moderately elevated temperatures

Abstract Incidence of parthenocarpic fruit, undeveloped flowers and flower abortion in tomato plants ( Lycopersicon esculentum Mill.) were compared under optimal temperature (OT, 28/22°C day/night) and chronic, mild high temperature conditions (HT, 32/26°C). Seeded fruits were found only under OT conditions, where 37±9% of all flowers developed into seeded fruit. However, flower aborted was also higher under OT, with an additional 24±7% of flowers aborted under optimal temperature conditions, compared to only 4±1% of flowers aborted under HT conditions. Under HT, most flowers (53±8%) developed into parthenocarpic fruit, and the remainder (43±7%) stayed on the plant as undeveloped flowers. A slow transition of undeveloped flowers to parthenocarpic fruit was also observed under HT. Factors determining whether flowers abort, develop parthenocarpically, remain on the plant without developing further, or develop into seeded fruit were discussed in relation to carbohydrate availability and the presence of seeded fruit on the vine.

Effects of irrigation frequency and scheduling on fruit production and radial fruit cracking in greenhouse tomatoes in soil beds and in a soil-less medium in bags

Abstract The effects on yield and radial fruit cracking of 2 media (soil in beds and soil-less medium in bags) and 2 drip-irrigation frequencies (once and 4 times daily) were determined for 4 greenhouse tomato (Lycopersicum esculentum L. Mill.) cultivars. For plants grown in soil-less medium, 2 tensiometer-controlled, drip-irrigation scheduling methods were compared. ‘Michigan’—‘Ohio’ hybrid fruit cracked significantly more than the 3 remaining cultivars, but did not differ in production of total and No. 1 fruit. The amount and severity of fruit cracking was least from the soil-less, bag-cultured plants. Total mean fruit weight was greatest from soil-grown plants. Although no differences in cracking occurred in the fruit from soil-less, bag-cultured plants, those whose irrigation was based on soil-less medium tensiometer readings produced lower total mean fruit weight than those whose irrigation was based on soil tensiometer readings. Number and weight of defective fruit was lowest from plants grown in soil-less medium and whose irrigation was based on soil tensiometer readings, and greatest from soil-grown plants. Fruit cracking was reduced by increasing the irrigation frequency from 1 to 4 times daily.

CO2 enrichment of greenhouse tomatoes using a closed-loop heat storage: Effects of cultivar and nitrogen

Abstract Spring crops of soil-grown greenhouse tomatoes (Lycopersion Lycopersicum (L.) Karst ex. Farw cultivars MO and TR-VE 23) were provided with three levels of nitrogen addition with and without added CO2. Using a closed-loop solar collection/storage system, crops could be CO2-enriched for 76–77% of the daylight hours. CO2 enrichment increased No. 1 grade fruit weight by 14 and 27% and by 4 and 18% for both cultivars in 1981 and 1982, respectively. Although the method and amount of nitrogen application differed between 1981 and 1982, a trend was seen in both years for low nitrogen treatments to produce a greater response to CO2 enrichment than high nitrogen treatments. A trend was also seen in both years for low nitrogen treatment to depress yield and quality in the non-enriched house, but to have no effect in the enriched house. This trend was particularly apparent in the cultivar with lower vegetative vigor, which also responded more overall to CO2 enrichment than the cultivar with greater vegetative vigor.

Diurnal malate and citrate fluctuations as related to nitrate and potassium concentrations in tomato leaves

Abstract Two experiments were conducted to determine if malate and citrate change diurnally, if these changes are light dependent, and how these changes relate to K+ and NO3 −1 levels. Malate concentration in tomato leaves was shown to increase during the day and decrease at night. The inverse occurred with citrate. The dependency of the changes on light was demonstrated for malate, but not for citrate. A relationship with NO3 − assimilation and K+ recirculation may explain the changes in malate concentration.