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D.J. Cantliffe

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.

Open access

J. T. Watkins and D. J. Cantliffe

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

J. T. Watkins and D. J. Cantliffe

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.

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Mustafa M.A. Elballa and D.J. Cantliffe

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.

Open access

D. J. Cantliffe and R. W. Robinson

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

A. C. Guedes and D. J. Cantliffe

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

S. C. Phatak and D. J. Cantliffe

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

D. J. Cantliffe and E. C. Tigchelaar

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

J.T. Watkins, D.J. Cantliffe, and M. Sachs

Abstract

Concentrations of O2 greater than 21% stimulated germination rate of Capsicum annuum L. (sweet pepper) at 25°C but inhibited germination rate at 15°. At a 10% O2 concentration, germination rates were reduced at both temperatures. Gibberellins A4A7 (GA4+7) increased germination rates at 15° and 25° in air. At 25° in 100% O2, germination rates of GA-treated and nontreated seeds were the same. At 15° and 100% O2, germination rates were increased slightly by GA4+7 application; however, the rates were slower than in air. Total respiratory activity at 25° was higher in 100% O2 than in air. High O2 concentrations did not affect the proportion of respiration which was in the cyanide-sensitive and -resistant pathways. Cyanide-resistant respiration comprised only a small percentage of total respiratory activity. At 15°, total respiration and the cyanide-sensitive and -resistant components were similar regardless of O2 treatment. The addition of GA increased respiratory activity only after radicle emergence occurred. Thus, germination rate of pepper seed can be increased by increasing temperature, higher O2 concentrations at the higher temperature, and GA4+7 at normal and low temperatures. GA appears to affect germination through metabolic events which occur before radicle emergence and which do not include alteration of respiratory activity.

Free access

Yu Sung, D.J. Cantliffe, and R.T. Nagata

Lettuce seeds differentially fail to germinate at temperatures above 21C according to genotype. Twenty-one lettuce lines were screened for their ability to germinate at temperatures from 24C to 36C. Four cultivars, `Dark Green Boston', `Valmaine', `Floricos 83', and `PI251245', were selected for this study because of their range of ability to germinate at temperatures above 24C. Seeds of the four cultivars were collected from mother plants grown in growth chambers at 20/10C(day/night temperature), 25/15C, 30/20C and 35/25C. Seeds were germinated on a thermogradient table from 24C to 36C under light (12 h). Seeds from `Floricos 83' produced above 30C had higher germination percentage at 33C and 36C than those produced below 30C temperatures. At 30C germination temperature seeds of `Valmaine' produced above 30C had 98% germination compared to 45% of those produced below 30C. `Dark Green Boston' seeds produced at 35C had higher germination percentage(70%) at 30C than those produced at other temperatures. Seeds collected from the mother plant grown above 30C day temperatures had greater germination than those grown below 30C.