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91 WORKSHOP 8 (Abstr. 1042-1045) Seed Vigor Testing and Utilization

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Author:

91 WORKSHOP 8 (Abstr. 1042-1045) Seed Vigor Testing and Utilization

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Abstract

It is beyond the purpose of this presentation to review all the definitions for the term “vigor” as applied to seeds. So far, no one definition has been accepted, and perhaps it is not yet time to settle on one definition until we know more about the subject.

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flower seeds, e.g., summer sowing for fall planting or winter sowing for spring planting. Vigor tests help determine failures in emergence and stand establishment and identify the level of physiological aging of a seed lot and its potential for the

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germination time and speed, and to calculate seed vigor, petri dishes were checked daily, and the number of germinated seeds was recorded. Mean time to germination (MTG) is an index of seed germination speed and velocity ( Ellis and Roberts, 1981 ) and is

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The environment that seeds experience during development, storage, and planting significantly affects seed vigor. Yet, relatively few studies have focused on how environment during seed development affects seed vigor. Our objective was to compare vigor of seeds developed in summer vs. winter. Lettuce (Lactuca sativa L.) seeds from six cultivars were developed in summer and winter at Yuma, Ariz. Seed vigor of these seedlots was compared using field plantings and growth chambers (at 20, 25, 30, and 35C). Seed vigor was greater for seed produced during summer than for that produced during winter, based on greater field emergence, higher germination percentages, and longer roots. These seedlot differences in vigor were greatest at 35C. Another way to estimate seed vigor is by ion leakage from seeds. Fewer ions leaked from seeds produced in summer than from those produced in winter. Thus, lettuce seed is more vigorous when produced in summer than in winter, and ion leakage is a good indicator of that vigor.

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Both seed viability and vigor directly affect the performance of seeds planted to regenerate the crop. Although seed quality can influence many aspects of performance (e.g., total emergence, rate of emergence), this presentation will primarily examine the relationship of seed vigor to one aspect of performance - crop yield. Reductions in yield can be indirectly related to low seed vigor if the low vigor seed results in plant populations that are below a critical level. Thus, we investigated the direct effects of seed vigor on yield in the absence of population differences for annual crops that are harvested at three stages; during vegetative growth, early reproductive growth or at full reproductive maturity. Seed vigor affects vegetative growth and is frequently related to yield in crops that are harvested during vegetative growth or during early reproductive growth. However, there is usually no relationship between vigor and yield in crops harvested at full reproductive maturity because seed yields at full reproductive maturity are usually not closely associated with vegetative growth. The use of high vigor planting seed can be justified for all crops; however, to insure adequate plant populations over the wide range of field conditions which occur during emergence.

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Previous experiments showed that a 10 day aerated water soak (water priming) increased red oak (Quercus rubra) seed vigor. After water priming most seed had split pericarps. Seed with split pericarps were observed to be more visorous than water primed seed without split pericarps. An experiment was conducted to determine if pericarp splitting could be used as an indicator of red oak seed vigor. The following experiment was conducted. Red oak seed from three open pollinated, half-sib families, were water primed for 10 days. Seed were separated into two groups, seed with split pericarps and without split pericarps, and a germination test conducted. Unprimed seed were used as a control. There were significant differences among the families in seed vigor (germination completeness, uniformity and speed). Primed seed with intact pericarps had lower seed vigor than primed seed with split pericarps and unprimed seed. The results suggest that pericarp splitting following water priming is an indicator of high seed vigor.

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ACC-derived ethylene production was used as an index of seed vigor of lettuce (Lactuca sativa L.), cabbage [Brassica oleracea (Capitata Group)], tomato (Lycopersicon esculentum Mill.), snap bean (Phaseolus vulgaris L.), and sweet corn (Zea mays L.) seeds. Seeds were aged at 40C and 93% relative humidity over saturated solution of KH2PO4 for various times to obtain seeds of differing vigor. Naturally aged lettuce seeds, differing in vigor, were also used. Depending on the seed type, 0.25 to 2 mm ACC (saturating dose) was needed to produce maximal amounts of ethylene. Seeds in the presence of ACC produced a much larger amount of ethylene than those in the absence of ACC, the ACC-derived ethylene could be detected before germination, and ACC had no adverse effect on germination. ACC-derived ethylene production paralleled vigor loss as determined by a decrease in percentage germination over a soak period required for complete germination of nonaged seeds (16 hours for lettuce, 24 hours for cabbage, and 48 hours for tomato and sweet corn), an increase in mean germination time (determined for lettuce only), and a decrease in seedling growth (determined for snap bean only). Second degree polynomial and logarithmic equations generated for the relationship of ACC-derived ethylene production to germination or growth parameters following seed aging, provided good to excellent fit. As a vigor test, the ACC-ethylene procedure has several advantages over the non-ACC ethylene procedure: It improves the sensitivity of the test by enhancing ethylene production, permits detection of small differences in vigor, and allows detection of ethylene before germination within a few hours of soaking. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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