Summnary. Corn (Zea wiiays L.) seed respiration rates during the first 30 hours of germination were compared with seedling growth 3 to 5 days after planting. Significant positive correlations were observed between rates of 02 uptake during imbibition and later stages of germination and seedling growth. Glutamic acid decarboxylase activity also was positively correlated with seedling growth. The highly significant correlations between respiratory quotients and seedling growth were negative.Seed metabolism during the initial hours of germination is evidently related somehow to seedling growth rates several days later. Whether this relationship is due to the dependence of synthetic processes and growth on respiratory energy, the fact that high respiration rates reflect high levels of metabolic activity, or to some other cause, remains to be determined.Many observations relating respiration to plant growth have been reported, but respiration-rates usually have been measured on activelyv rowing tissues. Thus, it cannot be unambiguously determined whether differences in respiration are a cause or a result of differences in growth. In this report, differences in respiration of germinating corn seeds are shown to precede differences in seedling growth and not to result from that growth.Throneberry and Smith (16) reported that loss of viability in corn seemed c!osely related to respiratory failure. The activities of malic and alcohol dehydrogenases and cytochrome oxidase were highly correlated with germination percentage. Indeed, the activity of the dehydrogenase enzymes provides the basis for the tetrazolium test for seed viabilitv (6). Frequently, however, the activity or lack of activity of a particular enzyme, or even group of enzymes, cannot be directly related to seed viability. In many cases, the activity of a certain enzyme mnay survive seed death (10). Conversely, some enzymes fail to show activity even in viable seed. Throneberry an(d Smith (16) found that different seed lots deviated from the regression line relating enzyme activ.ty to seed viability, depending on the enzym1ie assayed. The present investigation was predicated on the assumption that respiratory rates, depending on and reflecting the coordinated activity of many enzymes, might be more highly correlated with physiological characteristics of seeds such as viability or grovth than wvould be the activity of any one individual enizymlle. (18,19) and chilling injury in lima beans (20). Glutamic acid decarboxylase activity (GADA) is also related to seed germination (7) and has been used as an assay for seed storability (4, 5).In this investigation, we measured the respiration and GADA of samples of corn seeds having dif ferent levels of deterioration resulting from various longterm storage conditions. Respiration was measured between 2 and 30 hours after the start of imbibition as 02 uptake and as CO. evolution and compared with several indices of seed vigor and seedling growth. Materials and MethodsCorn seeds (Zea mavs L.) were stored for 4 years at...

The effect of temperature on hypocotyl elongation and seedling emergence of soybean [Glycine max (L.) Merr] varieties was studied under laboratory and field conditions. Hypocotyl elongation of darkgrown ‘Ford’ seedlings was severely inhibited at 25 C, but was normal at 15, 20, and 30 C. Hypocotyl elongation of ‘Hawkeye’ was normal at all four temepratures. Twenty‐five varieties were classified according to their ability to emerge from 10 cm of sand at 25 C. Distinct varietal differences in emergence ability were evident and appeared to be genetically controlled. Instances of erratic emergence of soybean plantings may be partially explained on the basis of depth of planting, variety, and soil temepratures during the germination period.

With an estimated 40 to 50 proposed seed vigor tests available, appropriate procedures for choosing the best single test or combination of tests are necessary. The objective of this study was to compare several statistical procedures for selecting the best single and multiple predictors of seedling emergence of wheat (Triticum aestivum L.). Twenty vigor tests and a field emergence trial were performed on 49 seed lots of ‘Hyslop’ soft white winter wheat. The best single predictors of field emergence were identified by calculating simple correlation coefficients. Multiple regression models were built to determine the best combination of tests for predicting field emergence. Col linear variables were examined for usefulness in linear index models. Among the single tests, glutamic acid decarboxylase activity, seedling root length, and tetrazolium vigor were the best predictors of seedling emergence, followed by seedling dry weight and respiratory quotient. The best combination of noncollinear multiple tests was that of tetrazolium viability, adenosine triphosphate, and respiratory O2 uptake. This combination gave an increase in predictive ability over the best single model. The best overall prediction of seedling emergence was obtained by calculating the geometric mean of multiple variables that were collinear and not suitable for a multiple regression model. The most suitable combination for the geometric mean was the highly correlated seedling root length, glutamic acid decarboxylase, and seedling dry weight tests. It appears that simple seedling growth measurements can be as effective as biochemical tests as indicators of seedling emergence of wheat. When building multiple regression models, only noncollinear variables as determined by factor analysis should be included. The calculation of the geometric mean of several vigor tests is proposed as a method for utilizing multiple tests that are highly correlated.

Spring plantings of tall fescue (Festuca arundinacea Schreb.) for seed production are common in the Pacific Northwest, but seed yields are negligible in the year of planting. Planting tall fescue seed crops with cereal companion crops could increase the profitability of seed production. The purpose of this study was to determine the competitive effects of spring cereals on growth, seed yield, and economic return of turf‐type tall fescue. ‘Bonanza’ tall fescue was interplanted iin 45‐cm rows with ‘Waverly’ spring wheat (Triticum aestivum L.), ‘Steptoe’ spring barley (Hordeum vulgare L.), and ‘Cayuse’ spring oats [Avena fatua var. sativa (L.) Haussk.] in 15‐ and 30‐cm rows. Experiments were initiated in March 1985 near Corvallis, OR, and repeated in 1986. Cereals reduced the photosynthetic photon flux density (PPFD) available for tall fescue seedlings, which caused transient increases in chlorophyll content and reduced soil temperature by 1.8 °C. Soil water content was decreased by competition from cereals, causing greater stomatal resistance and lower transpiration rate. Reduction in PPFD and soil water by cereals was responsible for low tall fescue tiller and dry matter production. Following cereal harvest, tall fescue regrowth and new tiller initiation were delayed until spring as a consequence of competition with cereals, resulting in fewer fertile tillers and a 61% reduction in firstyear (after planting) seed yield compared with no companion crop. Tall fescue growth and seed yield were similar with all cereals, row spacings, and combinations of row spacings and cereals. Second‐year (after planting) seed yield was 15% greater when fescue was established with cereals than when no companion crop was used. Dry conditions caused low grain yield and increased competition by cereals, and was partly responsible for poor economic returns; however, fescue planted with spring oats earned $139.00 ha‐1 more than monoculture over a 3‐yr period because of compensatory increases in second‐year seed yield. This suggests that turf‐type tall fescue establishment with cereals could be more profitable in spring with irrigation or in fall when water is not limiting.

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