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The influence of pre-sowing seed treatments on germination and emergence of tomato ‘New Yorker’ at low temperatures
Scientia Horticulturae, 9 ( 1 9 7 8 ) 1 1 9 - - 1 2 5
119
Elsevier Scientific P u b l i s h i n g C o m p a n y , A m s t e r d a m - - P r i n t e d in T h e N e t h e r l a n d s
THE INFLUENCE OF PRE-SOWING SEED TREATMENTS ON GERMINATION AND EMERGENCE OF TOMATO 'NEW YORKER' AT LOW TEMPERATURES
J. R U M P E L a n d I D A L I A S Z U D Y G A
Research Institute of Vegetable Crops, Shierniewice (Poland) (First received 5 J a n u a r y 1 9 7 8 ; in revised f o r m 18 April 1 9 7 8 )
ABSTRACT R u m p e l , J. a n d Szudyga, I., 1978. T h e i n f l u e n c e o f pre-sowing seed t r e a t m e n t s o n germinat i o n a n d e m e r g e n c e o f t o m a t o ' N e w Y o r k e r ' at low t e m p e r a t u r e s . Scientia Hortic., 9: 119--125. F r o m several seed p r e t r e a t m e n t s s t u d i e d , the h i g h e s t r e d u c i n g e f f e c t o n t i m e t o germinat i o n at 8, 12 a n d 15°C was o b t a i n e d t h r o u g h s o a k i n g t h e seeds in a s o l u t i o n c o n t a i n i n g p o l y e t h y l e n e glycol ( P E G ) a t - 7 . 5 bars p o t e n t i a l + f u s i c o c c i n 10 -s M for 7 days at 20°C. N e x t was P E G alone, a n d a s o l u t i o n of 1.5% each o f K N O 3 a n d K3PO , for 5 days at 24°C was t h i r d in effectiveness. T h e t i m e r e q u i r e d t o 50% g e r m i n a t i o n for t h e a b o v e p r e t r e a t m e n t s at 8°C was 15.7, 19.7 a n d 28.0 days, respectively, as c o m p a r e d t o 52.7 days for t h e unt r e a t e d c o n t r o l . These t i m e d i f f e r e n c e s decreased w i t h t h e increase o f t h e g e r m i n a t i o n temperatures. P r e t r e a t m e n t w i t h fusicoccin in H 2 0 r e s u l t e d in a c o m p a r a t i v e l y l o w e r e f f e c t o n t i m e to g e r m i n a t i o n . G A 3 a l o n e or w i t h k i n e t i n a n d e t h e p h o n applied via a c e t o n e at 8 ° C h a d o n l y a small r e d u c i n g e f f e c t o n t i m e t o g e r m i n a t i o n . No e f f e c t o n t i m e t o g e r m i n a t i o n was o b s e r v e d f r o m f u s i c o c c i n applied via a c e t o n e . P r e t r e a t m e n t o f seeds w i t h PEG, P E G + fusicoccin or K N O 3 + K3PO , as above, r e s u l t e d in h i g h e r seedling e m e r g e n c e in field c o n d i t i o n s as c o m p a r e d to t h e u n t r e a t e d seeds. H o w e v e r , n o significant d i f f e r e n c e s b e t w e e n t h e pret r e a t m e n t s were observed. T h e field e x p e r i m e n t was severely a f f e c t e d b y a b n o r m a l w e a t h e r conditions.
INTRODUCTION
Work at the Research Institute of Vegetable Crops in Skierniewice has shown the possibility for successful t o m a t o culture from direct sowing in the conditions of Southern and Central Poland. However, frequent low temperatures in May can reduce the germination rate and final emergence, thus causing problems with the establishment of the uniform and dense plant stands required for concentrated fruit maturity. A possibility of hastening the germination and emergence under cool weather conditions would have a significant value for introduction of the drilled t o m a t o culture. Our paper presents results of work on differe~lt pre-sowing treatments for increasing the seed germination and seedling emergence of t o m a t o under cool conditions. The work was aimed at getting physiologically active, but n o t ger-
120
minated, seeds which could be sown out in the dry state. The treatments in laboratory conditions included "priming" with polyethylene glycol (Heydecker et al., 1973, 1975; Heydecker, 1975 and personal communication; Bussell and Gray, 1976) and in dilute salt solution {Ells, 1963), soaking in fusicoccin (Lado et al., 1974; Ballio, personal communication), soaking in growth regulators {Braun et al., 1976) and priming in polyethylene glycol with fusicoccin. The best treatments from the laboratory work were tested for emergence under field conditions. MATERIALS AND METHODS
For both experiments seeds of cultivar 'New Yorker' were used. In the laboratory germination experiment {Experiment 1) the pretreatment was performed by soaking the seeds in one of the following solutions: (1) untreated control, dry; (2) polyethylene glycol " 6 0 0 0 " (PEG) a t - 7 . 5 bars potential, for 7 days at 20°C; (3) PEG as above with fusicoccin 10 -s M, at 20 ° C; (4) 1.5% KNO3 + 1.5% K3PO4, for 5 days at 24°C; (5) fusicoccin 10 -s M in H20, for 3 h; (6) fusicoccin as above and later germinated on filter paper moistened with the same solution; (7) fusicoccin 10 -s M dissolved in acetone, for 1 h; (8) gibberellic acid 10 -3 M (GA3) dissolved in acetone, for 1 h; (9) a combination of solutions: GA3 10 -3 M + kinetin 5 × 10 -4 M + ethephon 3.5 X 10 -3 M, dissolved in acetone, for 1 h. PEG is a chemical reagent known also under the trade name "Carbowax". PEG solution o f - 7 . 5 bars potential was made as reported {Michel and Kaufman, 1973) by dissolving 242.5 g "Carbowax 6 0 0 0 " in 1 litre of distilled water. Fusicoccin, a diterpene glucoside with molecular weight = 680 (Ballio et al., 1968), was prepared by dissolving the substance in a minute a m o u n t of ethanol and then making up to volume with distilled water (Ballio, 1976, personal communication). Seeds in Treatments 2, 3 and 4 were incompletely covered with the solution to ensure adequate aeration. Liquid lost by evaporation was mado up with water. After treatment, seeds were washed with distilled water and dried in an airflow at 20 ° C. All groups of seeds, including untreated control, were then placed for germination on 2 layers of filter paper in petri dishes. Each dish contained 100 seeds. Germination t o o k place in darkness at 8, 12 or 15 ° C. Seeds were considered to have germinated when radicles were about 1 mm long. Germination was recorded daily until no more radicles occurred for 3 consecutive days. There were 3 replicates of each treatment. In the field experiment {Experiment 2) a preliminary study was made on the influence of seed pretreatment on seedling emergence in natural growingconditions. Three seed pretreatments from the laboratory work were tested in
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the field: (2) PEG alone; (3) PEG + fusicoccin; (4) 1.5% of both KNO3 and K3PO4. The experiment was located on a medium heavy podsolic soil, fertilized prior to sowing with 112 kg N, 115 kg P2Os and 200 kg K20 ha -~. Seeds were sown in clumps of 10 seeds/clump on 2 May 1977. The distance between the clumps in the row was 25 cm and the spacing between the double rows was 100 + 35 cm. There were 24 clumps per plot of 4.05 m 2. Each treatment was replicated 4 times in a randomized block design. Seedlings were considered to have emerged when the cotyledons were fully unfolded. The weather conditions after sowing were unfavourable. High precipatation caused run-off and temporary water-logging prior to emergence on the experimental site. Late spring frosts occurred on 26, 27 and 28 May with temperatures of - 0.1, -2.1 and - 1.0 ° C, respectively. The mean air temperature in May was 12.5°C and that of soil at a depth of 5 cm was 14.8°C. Statistical analysis. -- The values for germination from Experiment 1 and those
for emergence in Experiment 2 were subject to analysis of variance. In Experiment 1 a single classification m e t h o d was used, individually for the 3 temperatures 8, 12 or 15°C. The analysis of Experiment 2 was made as for a randomized block design, separately for each of the determination times after 16, 21 or 29 days from sowing. The percentage of emergence was transformed before analysis into Bliss angles. The border differences were calculated with the use of the Student test by the significancy level o f P = 0.01 for Experiment 1 and P = 0.05 for Experiment 2. RESULTS E x p e r i m e n t I. E f f e c t s o f p r e - s o w i n g seed t r e a t m e n t s and t e m p e r a t u r e s on germination. -- As shown in Table 1, pretreatment of seeds had different ef-
fects on the time to 50% germination. Most effective was pretreatment 3, PEG with fusicoccin, which significantly reduced the time to germination compared to the untreated check and to all other treatments except for PEG alone at 12 ° C. The next best pretreatment was 2, PEG alone, whereas 4, KNO3 + K3PO4, was the third best pretreatment. KNO3 + K3PO4 was, compared to PEG alone, significantly less active in accelerating the germination at 8 and 12°C. At 15°C the effects of both pretreatments were equal. The effect of these 3 pretreatments was most pronounced at the lowest germination temperature and, as shown in Fig.l, at 8 ° C this was observed with increasing intensity with the increase in germination from 25 to 75%. Pretreatment 5, with fusicoccin in H20, resulted in a significant reduction in the time to 50% germination also, but to a much smaller e x t e n t than the
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above mentioned pretreatments. From both fusicoccin in H:O treatments (5 and 6) the latter was the most effective. Permeation of seeds with fusicoccin via acetone (7) had no effect. Pretreating with GA3 alone (8) or with GA3 combined with kinetin and ethephon (9) resulted, at 8 ° C, in a small stimulating effect on germination, but compared to other pretreatments, with the exception of fusicoccin in acetone (7), the effect was small. The percentage of final germination of the untreated seeds (1) had a tendency to increase with the germination temperature. All treated seed lots showed higher final germination at 8°C than the control seeds. These differences, however, were statistically non-significant. Experiment 2. Seedling emergence in the field after different pre-sowing seed treatments. -- Data presented in Table 2 indicate that all pretreatments improved the seedling emergence, as compared to the untreated control. The differences were significant at recordings after 16 and 29 days from sowing. All pretreatments under field conditions affected the emergence to a similar degree and none of the 3 pretreatments was superior to another, as was observed in Experiment 1 with germination, and also in a test for emergence conducted in the greenhouse (Fig.2). The lack of expected differences between the pretreatments might be due to the unfavourable growing-conditions mentioned earlier. This is evidenced by the decrease in the n u m b e r of seedlings in the time between the second and third recording and also by a relatively high experimental error. TABLE 1 Effect o f seed pretreatment~ and temperatures on seed germination of t o m a t o cultivar ' N e w Y o r k e r ' Treatment
(1) (2)
Untreated control PEG-7.5 bars for 7 d a y s a t 2 0 ° C (3) As above + fusicoccin 1 0 -s M (4) 1.5% KNO~ + 1.5% K3PO 4 f o r 5 d a y s at 2 4 ° C (5) F u s i c o c c i n 10 -~ M in H 2 0 f o r 3 h (6) As a b o v e + germinated on filter p a p e r moistened with fusicoccin (7) F u s i c o c c i n 1 0 -s M in acetone for 1 h (8) G A 3 10 -3 M in acetone for 1 h (9) GA 3 10 -3M+kinetin5x 10-4M + e t h e p h o n 3.5 x 10 -~ M in acetone for 1 h LSD, P = 0.01
Time to 50% germination (d a y s )
Percentage of final germination
8°C
12°C
15°C
8°C
12°C
15°C
52.7
22.0
9.3
80.7
94.0
97.0
19.7 15.7
8.0 7.0
4.0 3.0
92.9 91.4
98.0 93.9
95.3 96.7
28.0 46.0
12.3 20.0
4.0 7.3
93.3 92.5
92.6 96.3
94.6 95.8
40.0 53.3
17.7 20.7
7.7 9.3
83.8 82.5
92.7 92.9
93.7 94.2
45.7
21.3
9.0
92.2
93.3
93.7
45.3 2.33
20.3 1.74
10.0 0.92
92.5 NS
99.1 NS
98.4 NS
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TABLE 2 E f f e c t o f pre-sowing seed t r e a t m e n t s o n seedling e m e r g e n c e o f t o m a t o c u l t i v a r ' N e w Y o r k e r ' in field c o n d i t i o n s . S o w n o n 2 May 1977. M e a n air t e m p e r a t u r e in May 12.5°C. M e a n soil t e m p e r a t u r e in May a t 5 c m 14.8°C. Last spring frosts: o n 26.5, - 0 . 1 ° C ; o n 27.5, - 2 . 1 ° C ; o n 28.5, - 1 . 0 ° C Treatment
P e r c e n t a g e of seedling e m e r g e n c e a f t e r 16 days
Untreated control P E G - 7 . 5 bars for 7 days a t 20°C (3) As a b o v e + fusicoccin 10 -s M (4) 1.5% K N O , + 1.5% K3PO 4 for 5 days a t 24°C LSD, P = 0.05
21 days
29 days
4.8
18.3
12.8
12.9 15.7
25.7 24.4
20.4 19.9
15.6 7,3
21.4 NS
18.1 6.2
(1) (2)
60 L [ b
j
Control
4o} KNO3÷ K3PO4
un E 2
~
PEG PEG * Fus
[ 25
50
75
Percentage germination
Fig.1. E f f e c t o f t o m a t o seed p r e t r e a t m e n t o n d a v s f r o m sowin~ t o 2 5 . 5 0 a n d 75% ~erminat i o n a t 8°C. C o n t r o l = u n t r e a t e d ; K N O 3 + K~PO, = 1.5% o f each KNO~ + K3PO 4 for 5 days at 24°C; P E G = P E G - 7 . 5 bars p o t e n t i a l , for 7 days a t 20°C; P E G + Fus. = P E G - 7 . 5 bars p o t e n t i a l + fusicoccin 10 - s M for 7 days at 20°C.
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Fig. 2. Results of a greenhouse test on emergence of tomato seedlings after different presowing seed treatments. Number of seedlings emerged out of 50 seeds after 10, 14 and 17 days from sowing for each pretreatment, respectively, is given in parentheses. (1) PEG - 7 . 5 bars for 7 days at 20°C (2, 35, 40); (2) as (1) + fusicoccin 10 -s M (13, 40, 45); (3) 1.5% KNO 3 + 1.5% K3PO 4 for 5 days at 24°C (7, 36, 39); (4) GA 3 10 -3 M in acetone for 1 h (0, 19,33); (5) GA 3 10 -3 M + kinetin 5 × 10 -4 M + ethephon 3.4 × 10 -3 M (0, 12, 31); (6) fusicoccin 10 -s M in acetone for 1 h (0, 7, 23); (7) fusicoccin 10 -s M in H20 for 3 h (0, 14, 33); (8) as (7) + germinated on filter paper moistened with fusicoccin (0, 14, 30); (9) PEG in concentration as (1) for 7 days at 15°C (0, 38, 44); (10) untreated control (0, 22, 34).
DISCUSSION The results from Experiment 1 reveal that several seed pretreatment methods can promote tomato seed germination under cool conditions. High effectiven e s s w a s o b s e r v e d in t h e 3 p r e t r e a t m e n t s w i t h p r i m i n g o f s e e d s , w h e r e P E G w i t h f u s i c o c c i n ( T r e a t m e n t 3) w a s b e s t , P E G a l o n e ( T r e a t m e n t 2) w a s s e c o n d a n d K N O 3 + K3PO4 ( T r e a t m e n t 4) w a s t h i r d in a c t i v i t y . T h e c o m b i n a t i o n o f P E G a n d f u s i c o c c i n ( T r e a t m e n t 3) m i g h t b e a u s e f u l a d d i t i o n t o t h e p r i m i n g t e c h n i q u e s w i t h P E G ( H e y d e c k e r e t al., 1 9 7 3 ) a n d w i t h s a l t s o l u t i o n s (Ells, 1 9 6 3 ) in w o r k o n e s t a b l i s h m e n t o f d r i l l e d t o m a t o crops under cool conditions. P E G a l o n e a n d t h e s a l t s o l u t i o n s o f K N O 3 + K3PO4 c o m p a r e d in s i m i l a r
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work on tomatoes (Bussell and Gray, 1976) significantly reduced the germination time also, b u t the order of effect was opposite and the salt solution appeared to have a better influence on time to germination than PEG. These authors, however, used a different PEG pretreatment than reported here (with soaking of seeds at 10 and 15°C) and this might be responsible for the lower effect of PEG. The other seed pretreatments had relatively low effects and therefore seem to have no practical value. The results from Experiment 2 point o u t that pretreatment of t o m a t o seeds n o t only promotes the germination in laboratory conditions, b u t also increases the seedling emergence in the field. All 3 seed pretreatment methods resulted in similar effects in increasing the seedling emergence. These results for PEG or salt pretreatments are in agreement with earlier reports (Bussell and Gray, 1976), b u t do n o t fully confirm the results from Experiment 1 and the greenhouse test on emergence, where the best results were obtained with PEG combined with fusicoccin, whereas PEG alone and salt solution were in second and third place, respectively. The lack of differences in the effects of these treatments seems to be related to the abnormal weather conditions in the time from sowing to the last recording. Therefore, work on this problem is continued. Nevertheless, our results suggest that proper t o m a t o seed pretreatment can play an important role in early and uniform seedling emergence of drilled tomato culture under cool temperature conditions. ACKN OWLEDGEMENTS
The authors are grateful to Dr. A. Ballio, Professor at the University of Rome, Dept. of Biological Chemistry, for providing us with a sample of fusicoccin.
REFERENCES Ballio, A., Brufani, M., Casinovi, C.G., Cerrini, S., Fedeli, W., Pellicciari, R., Santurbano, B. and Vaciago, A., 1968. The structure of fusicoccin A. Experientia (Basel), 24: 631--635. Braun, J.W., Rao, V.S. and Khan, A.A., 1976. Release of lettuce seed thermodormancy by plant growth regulators applied in organic solvent. HortScience, 11 (1): 29--30. Bussell, W.T. and Gray, D., 1976. Effects of pre-sowing seed treatments and temperatures on tomato seed germination and seedling emergence. Scientia Hortic., 5 : 1 0 1 - - 1 0 9 . Ells, J.E., 1963. The influence of treating tomato seed with nutrient solutions on emergence rate and seedling growth. Proc. Am. Soc. Hortic. Sci., 83: 684--687. Heydecker, W., 1975. Seed priming -- the treatment of the future. Grower, Sept. 27. Heydecker, W., Higgins, J. and Guliver, R.L., 1973. Accelerated germination by osmotic seed treatment. Nature (London), 246: 42--44. Heydecker, W., Higgins, J. and Turner, Y.J., 1975. Invigoration of seeds? Seed Sci. Technol., 3: 881--888. Lado, P., Rasi Caldogno, F. and Colombo, R., 1974. Promoting effect of fusicoccin on seed germination. Physiol. Plant., 31: 1 4 9 - 1 5 2 . Michel, B.E. and Kaufman, M.R., 1973. The osmotic potential of polyethylene glycol "6000". Plant Physiol., 51: 914--916.
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Elsevier Scientific P u b l i s h i n g C o m p a n y , A m s t e r d a m - - P r i n t e d in T h e N e t h e r l a n d s
THE INFLUENCE OF PRE-SOWING SEED TREATMENTS ON GERMINATION AND EMERGENCE OF TOMATO 'NEW YORKER' AT LOW TEMPERATURES
J. R U M P E L a n d I D A L I A S Z U D Y G A
Research Institute of Vegetable Crops, Shierniewice (Poland) (First received 5 J a n u a r y 1 9 7 8 ; in revised f o r m 18 April 1 9 7 8 )
ABSTRACT R u m p e l , J. a n d Szudyga, I., 1978. T h e i n f l u e n c e o f pre-sowing seed t r e a t m e n t s o n germinat i o n a n d e m e r g e n c e o f t o m a t o ' N e w Y o r k e r ' at low t e m p e r a t u r e s . Scientia Hortic., 9: 119--125. F r o m several seed p r e t r e a t m e n t s s t u d i e d , the h i g h e s t r e d u c i n g e f f e c t o n t i m e t o germinat i o n at 8, 12 a n d 15°C was o b t a i n e d t h r o u g h s o a k i n g t h e seeds in a s o l u t i o n c o n t a i n i n g p o l y e t h y l e n e glycol ( P E G ) a t - 7 . 5 bars p o t e n t i a l + f u s i c o c c i n 10 -s M for 7 days at 20°C. N e x t was P E G alone, a n d a s o l u t i o n of 1.5% each o f K N O 3 a n d K3PO , for 5 days at 24°C was t h i r d in effectiveness. T h e t i m e r e q u i r e d t o 50% g e r m i n a t i o n for t h e a b o v e p r e t r e a t m e n t s at 8°C was 15.7, 19.7 a n d 28.0 days, respectively, as c o m p a r e d t o 52.7 days for t h e unt r e a t e d c o n t r o l . These t i m e d i f f e r e n c e s decreased w i t h t h e increase o f t h e g e r m i n a t i o n temperatures. P r e t r e a t m e n t w i t h fusicoccin in H 2 0 r e s u l t e d in a c o m p a r a t i v e l y l o w e r e f f e c t o n t i m e to g e r m i n a t i o n . G A 3 a l o n e or w i t h k i n e t i n a n d e t h e p h o n applied via a c e t o n e at 8 ° C h a d o n l y a small r e d u c i n g e f f e c t o n t i m e t o g e r m i n a t i o n . No e f f e c t o n t i m e t o g e r m i n a t i o n was o b s e r v e d f r o m f u s i c o c c i n applied via a c e t o n e . P r e t r e a t m e n t o f seeds w i t h PEG, P E G + fusicoccin or K N O 3 + K3PO , as above, r e s u l t e d in h i g h e r seedling e m e r g e n c e in field c o n d i t i o n s as c o m p a r e d to t h e u n t r e a t e d seeds. H o w e v e r , n o significant d i f f e r e n c e s b e t w e e n t h e pret r e a t m e n t s were observed. T h e field e x p e r i m e n t was severely a f f e c t e d b y a b n o r m a l w e a t h e r conditions.
INTRODUCTION
Work at the Research Institute of Vegetable Crops in Skierniewice has shown the possibility for successful t o m a t o culture from direct sowing in the conditions of Southern and Central Poland. However, frequent low temperatures in May can reduce the germination rate and final emergence, thus causing problems with the establishment of the uniform and dense plant stands required for concentrated fruit maturity. A possibility of hastening the germination and emergence under cool weather conditions would have a significant value for introduction of the drilled t o m a t o culture. Our paper presents results of work on differe~lt pre-sowing treatments for increasing the seed germination and seedling emergence of t o m a t o under cool conditions. The work was aimed at getting physiologically active, but n o t ger-
120
minated, seeds which could be sown out in the dry state. The treatments in laboratory conditions included "priming" with polyethylene glycol (Heydecker et al., 1973, 1975; Heydecker, 1975 and personal communication; Bussell and Gray, 1976) and in dilute salt solution {Ells, 1963), soaking in fusicoccin (Lado et al., 1974; Ballio, personal communication), soaking in growth regulators {Braun et al., 1976) and priming in polyethylene glycol with fusicoccin. The best treatments from the laboratory work were tested for emergence under field conditions. MATERIALS AND METHODS
For both experiments seeds of cultivar 'New Yorker' were used. In the laboratory germination experiment {Experiment 1) the pretreatment was performed by soaking the seeds in one of the following solutions: (1) untreated control, dry; (2) polyethylene glycol " 6 0 0 0 " (PEG) a t - 7 . 5 bars potential, for 7 days at 20°C; (3) PEG as above with fusicoccin 10 -s M, at 20 ° C; (4) 1.5% KNO3 + 1.5% K3PO4, for 5 days at 24°C; (5) fusicoccin 10 -s M in H20, for 3 h; (6) fusicoccin as above and later germinated on filter paper moistened with the same solution; (7) fusicoccin 10 -s M dissolved in acetone, for 1 h; (8) gibberellic acid 10 -3 M (GA3) dissolved in acetone, for 1 h; (9) a combination of solutions: GA3 10 -3 M + kinetin 5 × 10 -4 M + ethephon 3.5 X 10 -3 M, dissolved in acetone, for 1 h. PEG is a chemical reagent known also under the trade name "Carbowax". PEG solution o f - 7 . 5 bars potential was made as reported {Michel and Kaufman, 1973) by dissolving 242.5 g "Carbowax 6 0 0 0 " in 1 litre of distilled water. Fusicoccin, a diterpene glucoside with molecular weight = 680 (Ballio et al., 1968), was prepared by dissolving the substance in a minute a m o u n t of ethanol and then making up to volume with distilled water (Ballio, 1976, personal communication). Seeds in Treatments 2, 3 and 4 were incompletely covered with the solution to ensure adequate aeration. Liquid lost by evaporation was mado up with water. After treatment, seeds were washed with distilled water and dried in an airflow at 20 ° C. All groups of seeds, including untreated control, were then placed for germination on 2 layers of filter paper in petri dishes. Each dish contained 100 seeds. Germination t o o k place in darkness at 8, 12 or 15 ° C. Seeds were considered to have germinated when radicles were about 1 mm long. Germination was recorded daily until no more radicles occurred for 3 consecutive days. There were 3 replicates of each treatment. In the field experiment {Experiment 2) a preliminary study was made on the influence of seed pretreatment on seedling emergence in natural growingconditions. Three seed pretreatments from the laboratory work were tested in
121
the field: (2) PEG alone; (3) PEG + fusicoccin; (4) 1.5% of both KNO3 and K3PO4. The experiment was located on a medium heavy podsolic soil, fertilized prior to sowing with 112 kg N, 115 kg P2Os and 200 kg K20 ha -~. Seeds were sown in clumps of 10 seeds/clump on 2 May 1977. The distance between the clumps in the row was 25 cm and the spacing between the double rows was 100 + 35 cm. There were 24 clumps per plot of 4.05 m 2. Each treatment was replicated 4 times in a randomized block design. Seedlings were considered to have emerged when the cotyledons were fully unfolded. The weather conditions after sowing were unfavourable. High precipatation caused run-off and temporary water-logging prior to emergence on the experimental site. Late spring frosts occurred on 26, 27 and 28 May with temperatures of - 0.1, -2.1 and - 1.0 ° C, respectively. The mean air temperature in May was 12.5°C and that of soil at a depth of 5 cm was 14.8°C. Statistical analysis. -- The values for germination from Experiment 1 and those
for emergence in Experiment 2 were subject to analysis of variance. In Experiment 1 a single classification m e t h o d was used, individually for the 3 temperatures 8, 12 or 15°C. The analysis of Experiment 2 was made as for a randomized block design, separately for each of the determination times after 16, 21 or 29 days from sowing. The percentage of emergence was transformed before analysis into Bliss angles. The border differences were calculated with the use of the Student test by the significancy level o f P = 0.01 for Experiment 1 and P = 0.05 for Experiment 2. RESULTS E x p e r i m e n t I. E f f e c t s o f p r e - s o w i n g seed t r e a t m e n t s and t e m p e r a t u r e s on germination. -- As shown in Table 1, pretreatment of seeds had different ef-
fects on the time to 50% germination. Most effective was pretreatment 3, PEG with fusicoccin, which significantly reduced the time to germination compared to the untreated check and to all other treatments except for PEG alone at 12 ° C. The next best pretreatment was 2, PEG alone, whereas 4, KNO3 + K3PO4, was the third best pretreatment. KNO3 + K3PO4 was, compared to PEG alone, significantly less active in accelerating the germination at 8 and 12°C. At 15°C the effects of both pretreatments were equal. The effect of these 3 pretreatments was most pronounced at the lowest germination temperature and, as shown in Fig.l, at 8 ° C this was observed with increasing intensity with the increase in germination from 25 to 75%. Pretreatment 5, with fusicoccin in H20, resulted in a significant reduction in the time to 50% germination also, but to a much smaller e x t e n t than the
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above mentioned pretreatments. From both fusicoccin in H:O treatments (5 and 6) the latter was the most effective. Permeation of seeds with fusicoccin via acetone (7) had no effect. Pretreating with GA3 alone (8) or with GA3 combined with kinetin and ethephon (9) resulted, at 8 ° C, in a small stimulating effect on germination, but compared to other pretreatments, with the exception of fusicoccin in acetone (7), the effect was small. The percentage of final germination of the untreated seeds (1) had a tendency to increase with the germination temperature. All treated seed lots showed higher final germination at 8°C than the control seeds. These differences, however, were statistically non-significant. Experiment 2. Seedling emergence in the field after different pre-sowing seed treatments. -- Data presented in Table 2 indicate that all pretreatments improved the seedling emergence, as compared to the untreated control. The differences were significant at recordings after 16 and 29 days from sowing. All pretreatments under field conditions affected the emergence to a similar degree and none of the 3 pretreatments was superior to another, as was observed in Experiment 1 with germination, and also in a test for emergence conducted in the greenhouse (Fig.2). The lack of expected differences between the pretreatments might be due to the unfavourable growing-conditions mentioned earlier. This is evidenced by the decrease in the n u m b e r of seedlings in the time between the second and third recording and also by a relatively high experimental error. TABLE 1 Effect o f seed pretreatment~ and temperatures on seed germination of t o m a t o cultivar ' N e w Y o r k e r ' Treatment
(1) (2)
Untreated control PEG-7.5 bars for 7 d a y s a t 2 0 ° C (3) As above + fusicoccin 1 0 -s M (4) 1.5% KNO~ + 1.5% K3PO 4 f o r 5 d a y s at 2 4 ° C (5) F u s i c o c c i n 10 -~ M in H 2 0 f o r 3 h (6) As a b o v e + germinated on filter p a p e r moistened with fusicoccin (7) F u s i c o c c i n 1 0 -s M in acetone for 1 h (8) G A 3 10 -3 M in acetone for 1 h (9) GA 3 10 -3M+kinetin5x 10-4M + e t h e p h o n 3.5 x 10 -~ M in acetone for 1 h LSD, P = 0.01
Time to 50% germination (d a y s )
Percentage of final germination
8°C
12°C
15°C
8°C
12°C
15°C
52.7
22.0
9.3
80.7
94.0
97.0
19.7 15.7
8.0 7.0
4.0 3.0
92.9 91.4
98.0 93.9
95.3 96.7
28.0 46.0
12.3 20.0
4.0 7.3
93.3 92.5
92.6 96.3
94.6 95.8
40.0 53.3
17.7 20.7
7.7 9.3
83.8 82.5
92.7 92.9
93.7 94.2
45.7
21.3
9.0
92.2
93.3
93.7
45.3 2.33
20.3 1.74
10.0 0.92
92.5 NS
99.1 NS
98.4 NS
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TABLE 2 E f f e c t o f pre-sowing seed t r e a t m e n t s o n seedling e m e r g e n c e o f t o m a t o c u l t i v a r ' N e w Y o r k e r ' in field c o n d i t i o n s . S o w n o n 2 May 1977. M e a n air t e m p e r a t u r e in May 12.5°C. M e a n soil t e m p e r a t u r e in May a t 5 c m 14.8°C. Last spring frosts: o n 26.5, - 0 . 1 ° C ; o n 27.5, - 2 . 1 ° C ; o n 28.5, - 1 . 0 ° C Treatment
P e r c e n t a g e of seedling e m e r g e n c e a f t e r 16 days
Untreated control P E G - 7 . 5 bars for 7 days a t 20°C (3) As a b o v e + fusicoccin 10 -s M (4) 1.5% K N O , + 1.5% K3PO 4 for 5 days a t 24°C LSD, P = 0.05
21 days
29 days
4.8
18.3
12.8
12.9 15.7
25.7 24.4
20.4 19.9
15.6 7,3
21.4 NS
18.1 6.2
(1) (2)
60 L [ b
j
Control
4o} KNO3÷ K3PO4
un E 2
~
PEG PEG * Fus
[ 25
50
75
Percentage germination
Fig.1. E f f e c t o f t o m a t o seed p r e t r e a t m e n t o n d a v s f r o m sowin~ t o 2 5 . 5 0 a n d 75% ~erminat i o n a t 8°C. C o n t r o l = u n t r e a t e d ; K N O 3 + K~PO, = 1.5% o f each KNO~ + K3PO 4 for 5 days at 24°C; P E G = P E G - 7 . 5 bars p o t e n t i a l , for 7 days a t 20°C; P E G + Fus. = P E G - 7 . 5 bars p o t e n t i a l + fusicoccin 10 - s M for 7 days at 20°C.
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Fig. 2. Results of a greenhouse test on emergence of tomato seedlings after different presowing seed treatments. Number of seedlings emerged out of 50 seeds after 10, 14 and 17 days from sowing for each pretreatment, respectively, is given in parentheses. (1) PEG - 7 . 5 bars for 7 days at 20°C (2, 35, 40); (2) as (1) + fusicoccin 10 -s M (13, 40, 45); (3) 1.5% KNO 3 + 1.5% K3PO 4 for 5 days at 24°C (7, 36, 39); (4) GA 3 10 -3 M in acetone for 1 h (0, 19,33); (5) GA 3 10 -3 M + kinetin 5 × 10 -4 M + ethephon 3.4 × 10 -3 M (0, 12, 31); (6) fusicoccin 10 -s M in acetone for 1 h (0, 7, 23); (7) fusicoccin 10 -s M in H20 for 3 h (0, 14, 33); (8) as (7) + germinated on filter paper moistened with fusicoccin (0, 14, 30); (9) PEG in concentration as (1) for 7 days at 15°C (0, 38, 44); (10) untreated control (0, 22, 34).
DISCUSSION The results from Experiment 1 reveal that several seed pretreatment methods can promote tomato seed germination under cool conditions. High effectiven e s s w a s o b s e r v e d in t h e 3 p r e t r e a t m e n t s w i t h p r i m i n g o f s e e d s , w h e r e P E G w i t h f u s i c o c c i n ( T r e a t m e n t 3) w a s b e s t , P E G a l o n e ( T r e a t m e n t 2) w a s s e c o n d a n d K N O 3 + K3PO4 ( T r e a t m e n t 4) w a s t h i r d in a c t i v i t y . T h e c o m b i n a t i o n o f P E G a n d f u s i c o c c i n ( T r e a t m e n t 3) m i g h t b e a u s e f u l a d d i t i o n t o t h e p r i m i n g t e c h n i q u e s w i t h P E G ( H e y d e c k e r e t al., 1 9 7 3 ) a n d w i t h s a l t s o l u t i o n s (Ells, 1 9 6 3 ) in w o r k o n e s t a b l i s h m e n t o f d r i l l e d t o m a t o crops under cool conditions. P E G a l o n e a n d t h e s a l t s o l u t i o n s o f K N O 3 + K3PO4 c o m p a r e d in s i m i l a r
125
work on tomatoes (Bussell and Gray, 1976) significantly reduced the germination time also, b u t the order of effect was opposite and the salt solution appeared to have a better influence on time to germination than PEG. These authors, however, used a different PEG pretreatment than reported here (with soaking of seeds at 10 and 15°C) and this might be responsible for the lower effect of PEG. The other seed pretreatments had relatively low effects and therefore seem to have no practical value. The results from Experiment 2 point o u t that pretreatment of t o m a t o seeds n o t only promotes the germination in laboratory conditions, b u t also increases the seedling emergence in the field. All 3 seed pretreatment methods resulted in similar effects in increasing the seedling emergence. These results for PEG or salt pretreatments are in agreement with earlier reports (Bussell and Gray, 1976), b u t do n o t fully confirm the results from Experiment 1 and the greenhouse test on emergence, where the best results were obtained with PEG combined with fusicoccin, whereas PEG alone and salt solution were in second and third place, respectively. The lack of differences in the effects of these treatments seems to be related to the abnormal weather conditions in the time from sowing to the last recording. Therefore, work on this problem is continued. Nevertheless, our results suggest that proper t o m a t o seed pretreatment can play an important role in early and uniform seedling emergence of drilled tomato culture under cool temperature conditions. ACKN OWLEDGEMENTS
The authors are grateful to Dr. A. Ballio, Professor at the University of Rome, Dept. of Biological Chemistry, for providing us with a sample of fusicoccin.
REFERENCES Ballio, A., Brufani, M., Casinovi, C.G., Cerrini, S., Fedeli, W., Pellicciari, R., Santurbano, B. and Vaciago, A., 1968. The structure of fusicoccin A. Experientia (Basel), 24: 631--635. Braun, J.W., Rao, V.S. and Khan, A.A., 1976. Release of lettuce seed thermodormancy by plant growth regulators applied in organic solvent. HortScience, 11 (1): 29--30. Bussell, W.T. and Gray, D., 1976. Effects of pre-sowing seed treatments and temperatures on tomato seed germination and seedling emergence. Scientia Hortic., 5 : 1 0 1 - - 1 0 9 . Ells, J.E., 1963. The influence of treating tomato seed with nutrient solutions on emergence rate and seedling growth. Proc. Am. Soc. Hortic. Sci., 83: 684--687. Heydecker, W., 1975. Seed priming -- the treatment of the future. Grower, Sept. 27. Heydecker, W., Higgins, J. and Guliver, R.L., 1973. Accelerated germination by osmotic seed treatment. Nature (London), 246: 42--44. Heydecker, W., Higgins, J. and Turner, Y.J., 1975. Invigoration of seeds? Seed Sci. Technol., 3: 881--888. Lado, P., Rasi Caldogno, F. and Colombo, R., 1974. Promoting effect of fusicoccin on seed germination. Physiol. Plant., 31: 1 4 9 - 1 5 2 . Michel, B.E. and Kaufman, M.R., 1973. The osmotic potential of polyethylene glycol "6000". Plant Physiol., 51: 914--916.