Agriculture Reference
In-Depth Information
for 72 h provided the most consistent correlation with stand emergence at three planting dates for sorghum
[
Sorghum bicolor
(L.) Moench] (Ibrahim et al., 1993). Recent recommendations for AA of corn suggests
the use of 45°C for 72 h instead of 42°C for 96 h (TeKrony, 1996, personal communication; Goggi, 1996,
personal communication). Until recently, present AA test recommendations utilized water to achieve a
100% RH aging environment. For most small-seeded crops, this results in rapid water uptake and seed dete-
rioration. To retard moisture uptake, Zhang and McDonald (1996) recommended that saturated salt solu-
tions be substituted for water to reduce the relative humidity of the AA environment thereby delaying seed
deterioration. Such a procedure not only permitted AA testing of small-seeded crops but reduced the inci-
dence of storage fungi on seeds during AA that altered results (Moreno and Ramirez, 1985; Kononkov and
Dudina, 1986; Onesirosan, 1986; Gupta et al., 1993; Shekaramurthy et al., 1994). Future AA test research
will continue to deine the optimum temperature, duration, and relative humidity conditions for speciic
crops.
Accelerated aging test results have been correlated with stand establishment for a wide range of crops,
including soybean (Hamman et al., 2002), wheat (Meriaux et al., 2007), ield corn (Woltz and TeKrony,
2001), sweet corn (Zhao et al., 2007), canola (Elliott et al., 2007), and cucumber (Demir et al., 2004). When
soybean and corn seeds were planted under stressful ield conditions, AA germination provided a higher
correlation predictability of ield emergence than did standard germination (Egli and TeKrony, 1995, 1996;
Woltz and TeKrony, 2001). The primary emphasis of early investigations of the AA test was predicting the
seed storage potential ability of different crops. This has been repeatedly demonstrated for crops such as
peanut (Perez and Aguello, 1995), soybean (Fabrizius et al., 1997), cotton (Freitas et al., 2002), corn (Shaw
et al., 2002) and slash pine (Singh and Singh, 1997).
When conducting an AA test, speciic temperatures of aging and duration of the test for a number of
crops have been presented (Hampton and TeKrony, 1995). It is important to be aware of the variables in the
test and the precautions that should be taken to ensure results are appropriate and reproducible. Some of
these include (TeKrony, 1995):
1. Use water-jacketed type of accelerated aging chamber;
2. Precisely monitor aging temperature and maintain at ± 0.3°C of the desired temperature;
3. Weigh (do not count) seeds and place a constant weight of seeds in the inner chamber;
4. Do not open the door of outer aging chamber during aging period;
5. Prevent water (from condensation) from dripping onto lids of inner chamber boxes if alternative
AA chamber (not water-jacketed types) is used;
6. Record time at start of aging period and remove seed from outer chamber at the exact number of
hours speciied and plant within ± 1.0 h after removal; and
7. Determine seed moisture of check sample after aging.
Conductivity Test
The conductivity test is a valuable seed vigor test for many crops and is a recommended ISTA vigor test
for peas (Hampton and TeKrony, 1995). Excellent reviews of this vigor test have been provided by Powell
(1986), Pandey (1992), and Hampton (1995). A comprehensive study of conductivity test variables was
reported by Loefler et al. (1988). Low quality seeds have poor membrane structure that allows the outward
diffusion of ions during imbibition that are detected by monitoring the electrolytes present in the steep
water (Simon and Mills, 1983). Usually, conductivity test results are obtained by soaking the prescribed
number of seeds (usually 25-50) in water for a speciied time (usually 24 hr) at 20 or 25°C and the leach-
ate conductivity determined with a conductivity meter (Fig. 8.3). The leakage from soybean seeds may be
controlled by three recessive genes (Verma and Ram, 1987). Mechanical damage leading to split seed coats
in soybean was also detected by the conductivity test (Oliveira et al., 1984).
