The investigation was carried out at the Outreach building, at the Bangladesh Sheikh Bujibur Rahman Agricultural University (BSMRAU), Gazipur during October to December, 2008. Brinjal seeds used in this experiment were supplied by the Agronomy Department of (BSMRAU). After recording the initial moisture content and germination percentage, seeds were kept in three containers: tin container, polythene bag and cloth bag and stored at room temperature (25°C) and RH for two months. Germination test and recording the moisture content (wet basis) was performed every 15 days interval beginning from collection of seeds up to 60 days to observe the rate of natural ageing in different containers.
Moisture content: Moisture content was determined by using high constant temperature oven method following International Rules for Seed Testing (Anonymous, 1999) in the seed technology laboratory of BSMRAU. Five (5.0) grams of seeds from each 3 containers were taken. The seeds were poured in a small container with cover and kept in an oven maintained at a temperature of 1030C±2 for a period of 17 hours. The moisture content of seeds (wet basis) was determined by the following formula.
Moisture content (%) = {(M2-M3)/(M2-M1)}X100
M1=Weight of container+ cover
M2=Weight of container + cover+ Brinjal seeds before drying.
M3= Weight of container + cover+ Brinjal seeds after drying.
Germination test: Germination test was conducted by following sand method. For germination, test seeds were soaked in water for overnight and placed in plastic tray with moist sand. 400 seeds were taken randomly from the seed samples of each container. 100 seeds of each sample were placed top of the paper in plastic box. For each test, four plastic boxes were used. The four plastic boxes were placed in room temperature for 15 days for germination. Seedlings were counted every day up to the completion of germination at 15 days. A seed was considered to be germinated as coat ruptured, plumule come out up to 5 mm in the following formula (Krishnasamy and Seshu, 1990).
Germination (%)=(Number of seeds germinated/Number of seeds tested) X 100
Seeds were stored at room condition in different containers and germination test performed at 27 October, 2008. Initial, 11 and 23 November and 22 December, 2008 were observed. Seedlings obtained from standard germination test were used for seedling evaluation. Normal or abnormal seedling, Fresh and Dead seeds were classified according to the rules of ISTA (1993).
Seedling vigor: Seed vigor is the sum total of all those properties in seed which, upon planting, result in rapid and uniform production of healthy seedlings under a wide range of environments including both favorable and stress conditions (Association of Official Seed Analysts, USA). However, the technique of vigor index (VI) includes following formula given by Maguire (1962).
VI={Number if seeds germinated (First count)/Number of days to first count} X 100
+ ...............+ {Number if seeds germinated (Last count)/Number of days to Last count} X 100
Seedling evaluation: Seedlings obtained from standard germination test were used for seedling evaluation. Normal or abnormal seedlings were classified according to the rules of ISTA. Seedling root and shoot length was measured on day 15 of the germination test. Ten plant samples from each plastic pot were harvested and root and shoot length of individual plant was recorded and their wet weight and dry weight were measured. After taking fresh weight, samples were kept in a drying oven for 72 hours at 70ºC temperature.
Insects and diseases: For observation of biotic factor that influence seed quality, 20 g of Brinjal seeds were taken and observed the numbers and kind of insects or pathogen were present. No biotic factors like insects and pathogen was observed during the storage period in all the containers. It might be due to the storage period was short (around 2 months) and the storage climate was not favorable for insects and pathogen activity for Brinjal seeds.
Recording of weather data: Reading of dry bulb and weight bulb temperature and relative humidity of inside the room and outside the room was recorded in 9.00 AM and 5.00 PM a day. Maximum and minimum temperatures were recorded from outreach room conditions of BSMRAU.