Determining the moisture content of Acacia seeds.

In a recent paper in Southern Forests , Jaganathan and co-workers indicated that the low constant-temperature drying method (LCTDM) (103°C for 17 h) is satisfactory for determining moisture content (MC) in seeds with physical dormancy (PY). Would this recommendation apply to Acacia , a large genus (1000+ species) with a seed coat so strong that seeds in the soil can maintain high viability for many decades? MC was assessed, using the LCTDM, in six Australian Acacia species by comparing intact seeds with those cut in half. Halved seeds of all species lost moisture rapidly and their mass had largely stabilised after about 2–3 h. Intact seeds had a wide variation in moisture-loss patterns. In some species, the testa was morphologically unchanged after 24 h at 103°C and this was associated with a relatively slow moisture loss. In other species, the testa had completely shattered after 8 h, leading to a rapid moisture loss. If the LCTDM is used to determine MC in Acacia species, it is advisable to employ a technique that substantially disrupts the testa. Moisture content (MC) is an important property of seeds, associated with many aspects of physiological seed quality. Acacias have very hard seed coats, which means that seeds can survive for decades in the soil, but in standard methods of determining MC (e.g. heating in an oven at 103°C for 17 h), the moisture in the seed might not be able to escape. The standard method can work for some Acacia species; however, to ensure accurate results, seeds should be halved before going into the oven. Image by Geoff Burrows. [ABSTRACT FROM AUTHOR]