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This study was conducted to test the potential of the radicle emergence (RE) test to predict normal germination percentage (NG) in seed lots of watermelon, lettuce and carrot. One seed lot of each species was aged at 100% RH and 45°C for different times to produce 14 aged sub-samples. The RE (≥ 2 mm radicle) was counted during a germination test (ISTA Rules) and NG was assessed at the end of the test. RE counts after 74 (watermelon), 40 (lettuce) and 120 hours (carrot) were significantly (P < 0.001) related to NG (watermelon, R 2 = 0.81; lettuce, R2 = 0.74; carrot, R2 = 0.81). RE counts at the same times were significantly related to NG in ten commercial seed lots of watermelon (R2 = 0.66, P < 0.01), nine lots of lettuce (R2= 0.94, P < 0.001) and eight lots of carrot (R 2 = 0.64, P < 0.05). The potential of the RE test to predict NG of both different lots within the same cultivar (watermelon, carrot) and lots from different cultivars (lettuce) is discussed.

Ethanol release was tested in relation to seed vigour measured by seedling emergence and controlled deterioration tolerance in radish, pepper, watermelon, aubergine, leek and onion seed lots. Ethanol release, measured with six lots from each species after four and eight hours at 40°C and 30% seed moisture, was highly negatively correlated with controlled deterioration tolerance (45°C, 48 hours, 20% seed moisture) in radish (r = 0.05, P < 0.05), with seedling emergence in watermelon (r = 0.99, P < 0.01) and to both traits in pepper (r = 0.87 to 0.94, P < 0.05), but not with any variable for aubergine and leek. One single case was significant between ethanol release after eight hours and controlled deterioration for onion seeds. Results indicate that there is a relationship between ethanol release and seed vigour, but this appears to be species dependent.

The present study elucidates the effect of matrix priming with vermicompost (VCP) on germination and seedling emergence of two onion seed lots under drought, salt and temperature stress conditions. Seeds treated with water was considered as hydropriming (HP) and untreated (NP) seeds were taken as control. Treated and untreated seeds were exposed to different levels of drought (10 and 15% PEG), salt (50 and 100 mM NaCl) and temperature (30 and 35°C) stresses. Priming with vermicompost improved the performance of onion seed as indicated by higher germination and seedling growth under stress conditions. Catalase, superoxide dismutase and ascorbate peroxidase activities were found to be significantly (P < 0.05) higher in the vermicompost treated seeds than hydroprimed and untreated seeds.

The potential of the electrical conductivity test (EC) of seed soak water in predicting germination of radish seeds (cv. Finclik) was examined. Due to radical protrusion, EC measurements over 14 hours cannot be carried out during soaking at 15 and 20 degrees C; eight hours of soaking is suggested for results in one working day. Regression models were developed between EC and percentages of normal and abnormal seedlings or not germinated (dead) seeds obtained for 60 artificially aged seed lots. The resulting regression models were tested to predict standard germination percentages of twelve commercially available radish seed lots having final germination ranging between 78 and 98%. EC was negatively related to percentage of normal seedlings (R-2 = 0.71, P < 0.001) and positively related to percentage of dead seeds (R-2 = 0.65, P < 0.01). Data suggested that the standard laboratory gemination test can be replaced by EC measurements carried out at eight hours soaking, shortening analysis time for the estimation of radish seed germination quality.

This work evaluated the possibility of shortening the duration of the controlled deterioration test and compared the ability of the shortened test and the routine CD (controlled deterioration) and AA (accelerated aging) vigour tests to identify differences in vigour of onion seed lots. The CD test was modified, so that seed moisture raising. equilibration and ageing were completed in a day, and in the subsequent germination test, radicle emergence following ageing was assessed regularly over the first 4 days. The routine CD (45 degrees C, 20% m.c. for 24h) and AA (41 degrees C 72h) tests were also conducted. Emergence was assessed in the field at two sowing dates and seed longevity was determined following storage at 5 and 25 degrees C for 9 months at 6 and 9% seed moisture content (m.c.) Both the CD and the shortened CD tests (SCD) were closely correlated with field emergence (CD, r = 0.91-0.92, p < 0.01; SCD 0.85 - 0.93. p < 0.01 - 0.05) and mean emergence time (CD, r = 0.77-0.90, p < 0.01-0.05; SCD, r = 0.75 0.97, p < 0.05 - 0.001). Germination fell during storage only in seeds held at 9% m.c. at 5 and 25 degrees C and both the CD and SCD tests clearly identified seed lots that showed a larger decline in germination. The standard germination test was unrelated (p > 0.05) to the seedling emergence in the field and longevity. These results indicate that a shortened controlled deterioration test of only 5 days for onion seeds can identify differences in seed lot vigour.

Summary A wide range of seedling emergence in commercial seed lots of watermelon (10 lots), melon (10 lots) and cucumber (9 lots), all with standard germinations above 98%, was seen in low temperature emergence (LTE), high temperature (HTE) and an 8 cm deep sowing (MSE) in the field and in salt stress conditions (SSE) in trays at 20°C. Final emergence was closely related to both the rate of emergence, measured as mean emergence time (MET; the reciprocal of the rate of emergence), and to the mean germination time (MGT; the reciprocal of the rate of germination) for physiological germination (2 mm radicle) in the laboratory at 25°C. Slower germinating and emerging lots, so-called low vigour lots, had lower levels of emergence in all sowings. Single early counts of physiological germination identified low vigour lots for all three species and are suggested as a quick routine test. The physiological age of the seed lots, determined using accelerated ageing (45°C in 100% relative humidity) and controlled deterioration (45°C and 20 or 24% moisture content), was significantly related to MGT which was higher (i.e. germination was slower) in physiologically older seed. Previous work suggests that cucurbit seeds appear to retain germination capacity over several years although ageing is reflected in a slower rate of germination (high MGT). MGT can also be described as the length of the lag period from the start of imbibition to radicle protrusion. We propose that this period is needed for the repair of the effects of ageing and is therefore longer in aged seeds.

The emergence of 19 commercial seed lots (10 in 2005 and 9 in 2006) of watermelon (Citrullus lanatus Matsum and Nakai, Thunb.) with laboratory germination >90% were compared in stressful conditions of low temperature (LTE, early spring), mechanical stress (MSE, 6 cm deep sowing) and salt stress (SSE, 200 mM NaCl). The emergence percentage ranged between 12 54% for LTE, 19 -75%, for MSE and 43 91% in 2005 and 35 80% at LTE, 13 82% at MSE, 45 92% at SSE in 2006. The radicle emergence of the lots was determined after controlled deterioration (CD) at 40 and 45°C in 2005, or at 45 and 47°C in 2006, with 20% or 24% moisture content for 48, 72, 96, 120, 144 hours in 2005 and 48, 72, 96, 120, 144, 168 hours in 2006. The accelerated ageing test was also conducted at the same temperatures and ageing durations in both years. The germination range of the seed lots increased in both CD and AA as the ageing period was extended. Germination after all combinations of CD was positively and significantly (p

The emergence of thirteen commercial seed lots (laboratory germinations from 86 to 93%) of 6 cultivars of pepper (Capsicum annuum) was compared in compost in an unheated greenhouse. A March sowing gave a low temperature emergence (LTE) of the lots from 71 to 96% and an August sowing, a high temperature emergence (HTE) from 63 to 93%. The physiological germination (radicle of 2mm long) of the lots was determined after controlled deterioration (CD) at 45°C and at 18, 20 and 22% moisture content (mc) for 24, 48, 72 and 96 hours. Germinations ranged from 74 to 92% for 24 hours at 18% mc and 3 to 95% for 96 hours at 22% mc and were signifi cantly and positively correlated with LTE (6 out of 12 correlations ) and HTE (9 out of 12 correlations). Germination after CD at 22% mc for 24 hours was strongly correlated with HTE (r= 0.86, p< 0.001) and LTE (r= 0.73, p< 0.01). Initial laboratory germination was not signifi cantly related to either LTE or HTE. Laboratory germinations after 4 and 8 month storage at 5°C and 8% mc were closely correlated (mostly p< 0.001) with CD germinations for all but three CD conditions, more so than was initial laboratory germination. Mean emergence time (MET) in the LTE was inversely related to CD germination (24 hours, 22% mc) for three lots of the cultivar Yaglik and four lots of the cultivar Demre Sivrisi. Slower emerging lots had lower germinations after CD. The CD conditions of 24 hours and 22% mc are suggested as a routine test for pepper to predict emergence performance and longevity in store. The practical implications of the fi ndings are discussed in relation to the production of uniform transplants in protected cultivation.

The effect of salt priming (KNO 3 , 20°C, 3%, 6 d) on germination at seven and 14 days after planting and on root and shoot lengths of watermelon (Citrullus lanatus (Thunb.) Matsum and Nakai) seed lots harvested at a range of intervals from anthesis and at two levels of temperature was investigated during the years 2000 and 2001. Untreated seeds of 15, 20, 25 and 30 DAA (days after anthesis) were unable to germinate and final germination was lower than 20% in subsequent harvests until 60 DAA at 14°C. While at the same temperature treated seeds had germinated as early as 20 DAA and reached to 66% and 51% in 40 (2000) and 35 DAA ( 2001), respectively. Germinated seeds were unable to grow shoots at 14°C in either year. At 18°C, treatment was not effective on germination percentages at day seven in all three lots in 2000 but improved root and shoot lengths. The advantage obtained from the treatment varied among the lots with a minimum benefit of an increase of 15 mm in root and 28 mm in shoot length, respectively. Priming increased germination percentages at day seven and final and root and shoot length of all seed lots in 2001. Germination percentages in treated seeds varied between 68% and 84% in seeds harvested 20 DAA and thereafter. The less mature the seeds the higher the benefit obtained from the treatment. Maximum root and shoot lengths were recorded in seeds of 35 DAA as 37 and 40 mm in the control and as 60 and 61 mm in treated, respectively. We concluded that salt priming can be useful for improving germination, seedling growth and uniformity of heterogeneously matured watermelon lots at low temperatures to produce well developed seedlings in early spring sowings.