CONTROLLED DETERIORATION TEST

The controlled deterioration test was carried out according to Matthews and Powell ( l 987a) w i t h s o m e m od i fications. For e a c h treatment, fou r rep l ic ates o f 20 g o f s e e d s , w i t h m o i s ture c o n te n t d e t e r m i n e d b y internationally recom mended procedures (1ST A, 1 985), were placed i n 1 2 cm x 1 8 cm aluminium foil packs for the controlled deterioration test. The volume of water required to raise the moisture content of each seed sample to 20% was calculated lIsing the formula:

V(cm3) =

r-�-:-��?

J

where MCO is the original moi stu re content of the seeds and W is the weight of seeds (g) in each sample.

The required volume of water was carefully added to the seeds in each foil pack with the use of a pipelte, and the packets were heat sealed leaving as small an air gap as possible, using a r ibbon sealer. The aluminium foi l packets were stored for 2 4 h i n a 5°C room to allow the seeds to equilibrate to 20% seed moisture conte nt.

The packets were then transferred to a germinator set at 40°C and left for the required number of days for controlled deterioration. Three controlled deterioration times were used; 1 , 2 and 4 day (24, 48, 96 h). Immediately after removing the samples from the 40°C treatment, seed moisture content and standard germination tests were done as described in Section One.

3. 10. DATA A NALYSIS

The 1 988- 1 989 season included three experiments (population density, row width and time of sowing experiment) which at harvest were further divided into time of harvest and pod position effec ts. These were treated as factorial experiments, rather than a nested split plot design, in order to estim ate the second order interaction effects. Thus in the population density experiment, there were two times of harvest, three population densities and two pod positions (a 2 x 3 x 2 factorial experiment) and similarly with the row width experiment. For the time of sowing experiment, the two harvests, with two sowings, and two pod positions were analysed as a 2 x 2 x 2 factorial experiment.

More factors were examined in the 1989- 1990 experiments, i.e. there were three harvests and three pod positions. The population density and row width experiments were therefore analysed as 3 x 3 x 3 factorial experiments, i.e. the population density experiment had three harvests, three population densities and three pod positions while the row width experiment had three harvests, three row widths and three pod positions. The time of sowing was a 3 x 2 x 3 factorial experiment with three times of harvest, two times of sowing and three pod positions. The time and method of harvest conducted in 1 9 89- 1 990 season had three methods of harvest and three times of harvest which was a 3 x 3 factorial experiment. In all experiments the two cultivars (pania and Princess) used were analysed separately.

Analysis of variance was used to determ ine the significance of differences between treatments for germination, hollow heart, conductivity, controlled deterioration, and thousand seed weight. Individual effects of population density, pod position and time of harvest were also analysed, including the combined

effects of any two or the three parameters (population density, pod position and time of harvest). Least significant differences (LSD's) was used to compare the means.

Due to the voluminous data obtained from these experiments, only selected analysed data which show the appropriate response of the seeds from a factor and combined factors without hidden interactions have been presented. Complete data are kept at the Seed Technology Centre, M assey University, New Zealand for reference.

3. 1 1. CANOPY ENVIRONMENT EXPERIMENT

3 . 1 1 . 1 . FIELD EXPERIMENT CANOPY ENVIRONMENT

The temperatu re within the c anopy of the crop was measured using thennometers (minimum / maximum) for all treatments in both the 1 988- 1 989 and 1 989- 1990 seasons. In each treatment, the thennometers (two in the 1 988- 1 989 season and three in the 1 989- 1990 season) were each tied to a bamboo stick which was set beside specific pods at given pod positions describ e d previously (Seed Moisture C ontent Determ ination 3 . 7 ) . Temperature readings were taken between 10:00 a.m. to 4:00 p.m. (high temperatures in the day) at one hour intervals daily from 10 days before the last harvest.

3 . 1 1 .2. ENVIRONMENT READ FROM DATA LOGGER

Seeds of cv. Princess were hand sown on 5 November 1989 in three 1 m x 2

m plots. Each plot consisted of 100 kg super pack potting mix (Smith Potting Mix, Smith Soil Industries Ltd., Auckland, New Zealand). For each plot, six rows 20 cm apart were sown with seeds at approximately 3 cm depth. Two seeds per position were sown at 10, 5 and 2.5 cm intrarow spacings in separate plots . These were then thinned to one plant per intrarow space upon establishment to obtain a population density of 50, 1 00

Tem perature and rel a tive h u m i dity within the c anopy of each pea population density were monitored using a data logger (current monitor) with automatic print out system (Current Monitor, Measumeter II, Analogic AN25MOO, Electric Measurement and Control Ltd., A uckland, New Zealand) at one hour intervals from 9:00 a.m. to 5:00 p.m. each day from 20 days after pod setting until m aturity. The temperature and relative humidity were monitored from probes tied on bamboo sticks and set beside the third podding truss.

Temperature in di fferent parts of the canopy was monitored using a multipoint recorder (Honeywell Versaprint Single-pen and Multipoint Recorder, Yamatake, Model J 1 5 3 X 8 9C-52). For e ac h plot, three temperature probes tied to a bamboo stick were set beside a pod classified either as a top , m iddle or bottom pod as described previously (Seed Moisture Content Determination 3.7).

For 1990- 199 1 , a high population density of 200 plants m-2 of cv. Pania and cv. Princess were each sown in 1 m x 2 m plots on 29 October 1 990 following the methods used in 1 989- 1 990. The temperature and relative humidity within the canopy were monitored from pod development to maturity with the same data logger used in 1989- 1 990.

CHAPTER FOUR RESULTS