To test the effects of seed production environment and post harvest
management on seed yield and quality of peas and flax, a series of experiments were conducted over the three years 1998, 1999 and 2000, at Henfaes Research Centre, University of Wales, Bangor. Seed crops were grown in pots in a glasshouse and in the open air outside the glasshouse and in the field to test a range of sowing dates, different plant densities, and harvesting seed crops at different seed moisture contents to look at the effect of plant growing environment and different stages of seed development on seed yield and quality (viability and vigour). Experiments were also performed on post-harvest management of seeds. Seeds were dried for different amounts of time and at different temperatures, and using different drying methods (floors) and their germination and vigour tested.
The availability of quality seed is one of the major constraints in Bangladesh.
This thesis reports research conducted with the aim to increase seed yield and to
improve seed quality. The crops used for the purpose were combining pea (Pisum sativum L.), cv. Baccara and dual purpose linseed-flax (Linum usitatissimum L.), cvs. Tomba and Alice.
A series of experiments were performed to increase seed yield and to develop
seed quality testing techniques and to produce high vigour seeds. In this thesis,
Chapter 1 introduces the research and its background and comments on the seed quality problems of Bangladesh. Chapter 2 is a review of the literature on which this research is based. Chapter 3 describes some initial research experiments conducted to develop seed quality (vigour) testing techniques. Accelerated ageing and controlled deterioration were both compared. It was found that controlled deterioration was preferable to accelerated ageing as after accelerated ageing due to high humidity especially flax seeds became sticky and were difficult to separate and count for other tests without causing damage. Electrical conductivity was unsuitable for flax as the conductivity per seed and the increase in conductivity after ageing was much lower than in peas and the large decreases in emergence that occurred with 24 hours ageing
were associated with only small increases in conductivity. It was concluded that pea seeds should be placed in sealable containers at a seed moisture content around 19% and at temperature of 50°C for 8 days and flax seeds should be placed in sealable small vials at similar seed moisture content and at a temperature of 50°C for 36 hours for controlled deterioration.
Research was conducted to test a range of sowing dates, between 01.03.99 and
07.06.99 and in this way covering a wide range of environmental situations. Seed yield and seed quality of two species i.e. peas and flax were measured and compared. It was found that seed yield and seed vigour generally decreased in both species by delayed sowing and flax was more affected than peas. In both species the decrease in yield due to delayed sowing was due to decreases in all yield components. In peas the effects were significant for number of seeds per m2, number of seeds per plant and number of seeds per pod but not for number of pods per m2 and per plant. In flax the effects were significant for number of seeds per m2, number of capsules per plant, number of seeds per plant and number of seeds per capsule but not for number of capsules per m2. In peas sowings made between 15.03.99 and 25.04.99 had similar vigour but in flax sowing made on 12.04.99 had the highest vigour.
Sowing density studies were performed in a glasshouse and under field
conditions. They provided evidence that high density produced seeds of poorest
quality for both species under both environmental conditions (glasshouse and field). For seed yield the two species performed differently. As density increased in glasshouse seed yield per plant decreased in both species but in the field as density increased seed yield per plant decreased but seed yield per unit area increased in peas up to the highest density and decreased in flax from the lowest density. In peas as density increased, number of pods per plant, number of seeds per plant, number of seeds per pod, seed weight per plant, straw dry weight per plant and 1000 seed weight decreased, but number of pods per m2, number of seeds per m2, seed weight per m2 and straw dry weight per m2 increased as there were more plants at higher densities. In flax as density increased, number of capsules per plant and per m2, number of seeds per plant and per m2, number of seeds per capsule, seed weight per plant and per m2,
1000 seed weight and straw dry weight per plant decreased. Only straw dry weight per m2 increased as there were more plants at higher densities. In peas the effects were significant for number of pods per m2, seeds per m2, number of seeds per plant and number of pods per plant but not for number of seeds per pod. In flax the effects were significant for number of capsules per plant, number of seeds per plant and number of seeds per capsule but not for number of capsules per m2 and number of seeds per m2. It was found that intermediate density produced highest vigour seeds, though the effects of density on seed vigour were not significant.
Harvesting seed crops at different moisture content provided evidence that in
both species seed vigour appeared after physiological maturity and continued until some time after physiological maturity and then declined as harvesting was delayed. It was observed that seed vigour was highest when seed moisture content was lowest. The results of the present study provided contrasting evidence against Harrington's hypothesis about seed longevity and deterioration as maximum seed quality was not attained at physiological maturity and this did not start deteriorating after physiological maturity.
Post harvest management i.e. drying seed crops at different drying times,
temperatures and methods (floors) studies showed that peas were most sensitive to either high drying temperatures or longer drying times, but flax was more sensitive to the use of different drying floors. Drying temperatures of 40°C, 60°C, 80°C and 100°C were tested. It was found that only 40°C was suitable for peas and both 40°C and 60°C were suitable for flax. Seeds were also air dried on different floors, made of concrete, cowdung and soil. It was observed that concrete drying floor was suitable for both species.