FACTORS AFFECTING THE GERMINATION AND ESTABLISHMENT OF MONOGERM SUGAR BEET
3.1.3 Germination and Emergence Tests
The purpose of Experiment 1 was to test all five seedlots under conditions similar to those defined by the International Seed Testing Association (ANON 1966), as described in Section 2.3.3.
Germination counts were taken at intervals to determine the final germination percentages, and mean germination time (M.G.T.).
The procedure used for this test was as follows:-
1. Four groups of fifty seeds were counted out from each of the rubbed seed lots. Small, damaged and multigerm seeds were excluded as it was assumed further processing would also have removed them.
2. Four groups of fifty pelleted seeds were counted out from the commercial seed lots (without selection). The pelleting material was removed by washing.
3. All seeds were soaked in tap water for approximately l½ hours.
4. After a short period of air drying, each lot was placed in a 9 cm petri-dish containing three Whatmans' grade 181 filter papers and 5 ml of distilled water. The dishes were covered and placed in a temperature controlled incubator without illumination. The temperature was maintained at 20°C for 16 hours and 25°C for 8 hours per day (standard temperatures).
5. In this test germination counts were made initially at 2 day intervals, but the counting interval increased as germination approached completion.
6. Seeds were counted as having germinated when the radicle had forced the seed cap open and could be seen emerging from it.
7. As some of the selected seeds contained more than one true seed, despite the attempt to exclude them, they were considered to have germinated if one or more radicles appeared.
This procedure was chosen after considering the observations of Chetram and Heydecker (1967), Perry and Harrison (1974), and Hibbert and Woodwark (1969). Five ml of distilled water on three filter papers was known not to be excessive for germination. Experiment 1 was repeated at the end of the experimental period, (October 1980 - February 1981) to test for changes in germination performance in any of the seed lots.
The aim of Experiment 2 was to test seed germination at a lower temperature than the standard recommendation. It was suggested by Brown (1980) that spring-sown seed experiences seed bed temperatures well below those recommended for the standard test (ANON 1966). The procedure used was the same as in Experiment 1 except that the incubator was maintained at a constant 7.5 C, and also seed lots 2 & 5 were started two days before the others. This was because it was anticipated that these lots would take longer to reach the period when most seeds germinate. The temperature was selected to be low enough to allow germination, but not so low as to considerably prolong the duration of the experiment (Brown 1980).
The petri-dishes used in Experiment 2 which still contained ungerminated seeds after 30 or 32 days for Lots 1, 3 & 4, and 2 & 5 respectively were transferred to a cabinet at standard temperatures as germination at 7.5°C was considered to have been complete.
Germination counts were taken to assess the proportion of seeds which would germinate under standard conditions but not at 7.5°C. After a further 19 days germination at standard temperatures was considered complete.
The remaining ungerminated seeds were dissected to determine qualitatively if the true seeds were shrivelled or absent, or apparently normal.
Experiment 3 was a repeat of both Experiments 1 and 2 with advanced seed. The aim was to test the effect of advancing as a seed treatment, on germination performance at both standard and low temperatures. The advancing procedure used was as follows (Longden 1971):-
1. Samples from the pelleted seed lots were washed to remove the pelleting material.
2. Approximately 1000 seeds from each of the rubbed seed lots were weighed and placed in a 9 cm petri-dish.
3. Stage 2 was repeated with the de-pelleted seeds.
4. Tap water was added to each dish in an amount approximately equal to the weight of each seed sample in each dish.
5. The dishes were covered for 24 hours at room temperature, then uncovered with the contents spread out to dry for a further 48 hours.
6. Stage 5 was repeated twice, so that each seed sample received a total of three advancing cycles.
The seeds were then counted and set up as for Experiments 1 & 2, except that the 1½ hour pre-soak was omitted. The test at standard temperature was named Experiment 3 (i), and the low temperature test Experiment 3 (ii). It was noticed that during the advancing procedure some seeds germinated, and seed caps became detached from others, particularly in the de-pelleted samples. This was also observed by Longden (1971, 1973). However, only seeds entirely intact after the advancing treatment were selected for testing, and in Experiment 3 (i) seed Lots 3 & 4 were not used as there were too few intact seed left in the advanced seed stocks.
The aim of Experiment 4 was to test germination performance with a solution of Gibberellic acid (GA3) in place of distilled water. The procedure used was therefore the same as in Experiment 1 except that 5 ml of a 100 ppm solution of GA3 was placed in the petri-dishes, and germination counts were initially made at daily intervals. The concentration used had earlier been found to be optimal for improving germination performance if used in a 24 hour steep before testing (Scott et al 1972).
Experiment 5 was a repeat of Experiment 3 (i) (advancing and testing at standard temperature) except that, the tap water used for advancing was replaced by a 100 ppm GA3 solution. The aim of this experiment was to test the effects of advancing with GA3 on germination performance. As Experiment 5 was also effectively a treatment combination test, either additive effects or interactions may be observed.
The final test (Experiment 6) was an emergence test. Four replicates of 100 seeds or pellets from each seed lot were sown 2 cm deep in trays containing John Innes number 3 compost. The trays were placed in an illuminated (16 hour photo-period) glass house at approximately 16°C. The aim of this experiment was to examine the relationship between germination and emergence from compost, of the seed lots.
After 16 days seedlings were counted and cut off at soil level. The dry weights of the cut seedlings were assessed after oven drying for 24 hours at 90°C. A final count was made 27 days after sowing for slower emerging seedlings but no dry weights were recorded.
FACTORS AFFECTING THE GERMINATION AND ESTABLISHMENT OF MONOGERM SUGAR BEET
[Introduction & Contents] [Chapter One] [Chapter Two] [Chapter Three] [Chapter Four] [Chapter Five] [Chapter Six] [Chapter Seven]
[3.1] [3.1.1] [3.1.2.] [3.1.3] [3.1.4]
