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  • Author or Editor: D.J. Cantliffe x
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When lettuce seeds are imbibed and subjected to high temperature for periods of 72 h or more, dormancy known as thermodormaney is induced. Priming of three cultivars of lettuce (Lactuca sativa L.) seeds in 1% (w/v) K3 P O4 for 20 h in the dark reduced thermodormaney. Addition of 100 mg 6-benzyladenine (BA)/liter to the priming solution increased germination in petri dishes at 35C in `Green Lakes' from 65% in seeds that were primed without BA, to 92% when BA was added to the priming solution. In `South Bay' these percentages were 24% and 86%, respectively. Seedling emergence was improved in other lots of `Green Lakes' and `Montello' using soilless mix.

Free access

Abstract

The involvement of naphthaleneacetic acid (NAA), a synthetic auxin, and methyl-2-chloro-9-hydroxy-fluorene-9-carboxylate (chlorflurenol), an auxin transport inhibitor, in fruit set in cucumber (Cucumis sativus L.) was investigated. In the greenhouse, exogenously applied NAA and chlorflurenol enhanced fruit set depending on the position of application. In the growth chamber, when NAA was applied directly on the stigma, a small quantity moved into the ovary after 24 hours. However, when auxin was applied on the ovary, significant quantities of 14C NAA were detected in the ovary and other plant pieces. When NAA was placed on the peduncle, more accumulated in peduncle and stem sections than when NAA was placed on the stigma or ovary. Chlorflurenol applications to the peduncle inhibited movement of NAA out of the ovary and resulted in accumulation of auxin in that tissue. NAA movement in the intact plant was similar to that of excised sections: chlorflurenol applied to the peduncle reduced NAA movement out of the ovary. Thus, the regulation of fruit set by chlorflurenol may be through the restriction of auxin movement from the ovary. The increased auxin accumulation in the ovary may trigger fruit set and subsequent growth.

Open Access

Abstract

The importance of good quality, highly vigorous seed for agricultural production of crop plants cannot be overemphasized. With the ever increasing demands for a mechanized, energy-efficient type of agriculture, we have come to the stage where one plant is expected for every seed sown. Moreover, modern agriculture demands that each emerging plant grow and develop uniformly under a wide range of environmental conditions. The recent development of precision seeding equipment for small-seeded crops, improvements in chemical weed control, and the need for high plant populations and uniform plant stands for machine harvest has led to a growing interest in direct field seeding.

Open Access

Abstract

Germination rate of pepper (Capsicum annuum L.) seed was reduced and germination became less uniform as temperature was lowered from 25° to 15°C. There was no evidence of a leachable or extractable germination inhibitor being activated or formed during the exposure to low temperature. Auxin and kinetin applications did not alter germination rates, but gibberellins (GA3 and GA4+7) increased germination rates. GA4+7 was slightly more effective than GA3 in stimulating a germination rate increase. AMO 1618 effectively reduced germination rates.

Open Access

Abstract

Changes in soluble sugar composition of muskmelon (Cucumis melo L. var. reticulatus Naud.) mesocarp were followed throughout fruit development. Glucose and fructose, in nearly equal amounts, were the predominant sugars detected during the first 24 days after anthesis. Sucrose began to accumulate 24 days after anthesis and was the predominant sugar present in the ripe fruit. A soluble acid invertase (pH optimum 4.0 to 5.0) was detected in mesocarp extracts. Activity of acid invertase was highest in the young fruit and declined with development. Sucrose synthase activity was also detected in mesocarp extracts. Sucrose synthase activity increased between 18 and 24 days after anthesis and thereafter remained constant. Acid invertase and sucrose synthase appeared to be involved in the metabolism of sucrose during muskmelon fruit development.

Open Access

The effect of temperature on seedstalk development, seed yield and quality in carrot (Daucus carota L.) was investigated in growth chambers at constant day/night temperatures of 33/28, 28/23, 25/20, 23/18, 20/15, and 17/12 °C. Days to flowering, seedstalk height, number of umbels, and seed yield decreased linearly with increasing temperature from 17/12 to 33/28 °C. Continuous high temperature (33/28 °C) had a detrimental effect on germination as measured by a standard germination test and an accelerated aging test. Optimum germination of the progeny occurred at 20/15 °C; however, germination rate was faster when seeds matured at 23/18 °C. Seeds that developed at 33/28 °C produced seedlings with the lowest vigor, while those which developed at 20/15 °C produced seedlings with the highest vigor. Brief exposure of plants to 33/28 °C during anthesis or early seed development was as detrimental to seed yield as continuous exposure to 33/28 °C. Exposure to high temperature (33/28 °C) during late seed development had less effect on seed yield, and seed quality was improved. Progeny vigor was reduced greatly by seed development at continuous high temperature (33/28 °C), but was unaffected by brief exposure to 33/28 °C at anthesis, early, or late in seed development. These results suggest that high (33/28 °C) day/night temperatures during pollination, fertilization, or early stages of seed development can greatly reduce carrot seed yield and seed quality.

Free access

Abstract

The effects of water or 1% K3PO4 priming at 5°, 15° and 25°C for short durations on ‘Minetto’ lettuce (Lactuca sativa L.) seed germination at high temperatures were studied. Germination percentage and rate at 35° of seeds primed in K3PO4 were significantly higher than that of seeds soaked in water. Aeration improved the results of priming at 15° and 25°. A priming temperature of 15° was generally best. The effects of light during priming of ‘Mesa 659’, ‘Minetto’ and ‘Ithaca’ seeds in water, K3PO4, polyethylene glycol (PEG) or PEG + K3PO4 solutions at 15° for 6 or 9 hr and drying methods for primed seeds were also studied. Imbibition rates were higher with K3PO4. Primed seeds germinated more rapidly at 35° with K3PO4 alone or in combination with PEG. Air drying of primed seeds was better than oven drying. Seed priming in light increased germination percentage and rate of ‘Minetto’ and ‘Ithaca’, although neither cultivar is photosensitive.

Open Access

Abstract

Soil application of (2-chloroe thyl)phosphonic acid (ethephon) strongly promoted pistillate flower formation of cucumber. Soil treatment had a prolonged effect, for plants transplanted 4 weeks after the chemical was added to the soil were greatly modified in growth and development.

Open Access

Abstract

Good broadleaf weed control was achieved in table beets (Beta vulgaris L.) with cycloate, CNP, pebulate, lenacil, pyrazon (preplant application = pre), IMC 3950, TCA + pyrazon and pebulate (preplant incorporation = ppi) followed by pyrazone (postplant incorporation = post), while fair to good weed control was achieved with EPTC, propachlor and solubor. Poor weed control was obtained from CDEC, chlorpropham, pyrazon (post) and TCA. Yields expressed as $/ha or tons/ha were reduced by chlorpropham, lenacil, CNP and TCA. Nitrate-N was significantly increased in blades of beets by lenacil, pyrazon (pre) and CNP. The herbicides cyloate, CNP, EPTC, pebulate (ppi) — pyrazon (post), and TCA + pyrazon increased NO3-N concentrations in petioles. TCA + pyrazon and CNP increased NO3-N in beet roots, while CDEC, chlorpropham, solubor and pyrazon (post) decreased NO3-N. Total N concentration in the leaf blades was not affected by any of the herbicide treatments. Total N in petioles increased when TCA, chlorpropham, lenacil and CNP were used. TCA, chlorpropham, lenacil and CNP increased root total N.

Open Access

Abstract

Reciprocal bud grafts were made over various time periods from 0 to 48 hours between (2 chloroethyl)phosphonic acid (ethephon)-treated and non-treated monoecious cucumbers (Cucumis sativus L.) to determine the persistence of ethephon to induce pistillate (female) flowering. Ethephon had no influence on sex expression in stocks if treated scions were grafted onto non-treated stocks. If rootstocks were treated with 250 ppm ethephon in the 2-leaf stage, femaleness was increased in plants grafted within 8 hours. After that, ethephon had essentially no effect on sex expression. The number of leaves (2, 4, 6, or 8) present at the time of application did not improve the effectiveness of ethphon in promoting femaleness when grafts were made 48 hours after application.

Open Access