David W. Burger

Ineffectiveness of ethylene biosynthetic and action inhibitors in phenotypically reverting theEpinastic mutant of Tomato (Lycopersicon esculentum mill.)

Five-day-old, dark-grown seedlings of theEpinastic (Epi) tomato mutant (Lycopersicon esculentum Mill.) and its parent, cultivar VFN8, were used as a system for assessing the role of ethylene in theEpi phenotype. The distinguishing features ofEpi seedlings are an increase in hypocotyl diameter and reduced hypocotyl length. Treatment of VFN8 seedlings with 0.5 μl/liter ethylene closely mimicked theEpi phenotype. The rate of ethylene production by 5-day-old, dark-grownEpi seedlings was double that of VFN8 seedlings. Nevertheless, treatment ofEpi seedlings with inhibitors of ethylene biosynthesis (aminoethoxyvinylglycine or Co2+) or ethylene action (silver thiosulfate or norbornadiene) failed to normalize theEpi phenotype.Epi seedlings grown in sealed jars containing ethylene and CO2 adsorbants also expressed the characteristicEpi phenotype. The results indicate that the physiological lesion resulting from theEpi gene mutation is not simply an overproduction of ethylene.

Metabolic heat and CO 2 production rates during germination of melon (Cucumis melo L.) seeds measured by microcalorimetry

Metabolic heat and CO 2 production rates were measured by microcalorimetry during germination of two melon (Cucumis melo L.) accessions, Noy Yizre’el (a coldsensitive cultivar) and Persia 202 (a cold-tolerant breeding line), differing in their ability to germinate at low temperature (14°C). In seeds that were imbibed at either 14 or 25°C, both heat production rates (� ) and CO 2 evolution rates (RCO 2 ) were higher in Persia 202 compared to Noy Yizre’el. At 14°C, � and RCO 2 of intact Noy Yizre’el seeds remained close to zero and germination was inhibited, but metabolic activity increased with time in decoated seeds (testa removed) and most embryos germinated. The presence of the testa had less effect on metabolic activity or germination of Persia 202 seeds at 14°C. The ratio of � /RCO 2 (calorespirometric ratio) is an indication of the substrate being utilized for respiration, with lower values (~455 kJ mol ‐1 ) associated with carbohydrate substrates and higher values (~800 kJ mol ‐1 ) associated with lipid substrates. Removal of the testae of Noy Yizre’el seeds increased � /RCO 2 at 14°C, suggesting that improved oxygen supply to the embryo promotes a shift from carbohydrate to lipid respiratory substrates associated with germination. Consistent with this interpretation, when the hilum apertures of the seed coats were sealed with silicone, � , RCO 2 and � /RCO 2 of Noy Yizre’el seeds remained low and germination was inhibited at 25°C, while in Persia 202 seeds the same treatment had

Plant growth and development of Chrysanthemum and Ficus in aero-hydroponics: response to low dissolved oxygen concentrations

Abstract The growth of Chrysanthemum and Ficus plants in aero-hydroponics was reduced as the dissolved O2 concentration decreased; however, both species showed some adaptation to prolonged hypoxia in growth chamber experiments. Leaf number and plant height of Ficus plants grown in University of California (UC) mix or in water with an O2 concentration of 2 mg l−1 were lower than those in plants grown in O2-saturated water. Mathematical models were used to predict the time needed by Ficus plants growing in UC mix or aero-hydroponics to reach a particular leaf number. Ficus plants growing in O2-saturated water in aero-hydroponics produced leaves at the fastest rate.

Pollination effects on fruit production of ‘Star Ruby’ grapefruit (Citrus paradisi Macf.)

Abstract Flowers of ‘Star Ruby’ grapefruit were hand-pollinated with ‘Valencia’ orange ( C. sinensis (L.) Osbeck), ‘Marrs’ orange, ‘Ruby Red’ grapefruit ( C. paradisi Macf.) and ‘Star Ruby’ grapefruit pollen. Flowers cross-pollinated with ‘Ruby Red’ pollen produced more fruit than did self-pollinated flowers. Flowers cross-pollinated with either ‘Marrs’ or ‘Valencia’ pollen did not produce as many fruit as ‘Ruby Red’-pollinated flowers, nor did they produce more fruit than self-pollinated or open-pollinated flowers. Few fruit were produced when ‘Star Ruby’ flowers were not hand-pollinated. Less than 0.5% of ‘Star Ruby’ pollen germinated in 15–25% sucrose solutions, whereas between 6 and 21% of the pollen from ‘Valencia’, ‘Marrs’ and ‘Ruby Red’ germinated. The number of fully-developed seeds per fruit was increased only when ‘Marrs’ pollen was used. These data show that ‘Star Ruby’ produces very little functional pollen and few functional ovules, and suggests that ‘Star Ruby’ has weak parthenocarpic ability.