Equations for predicting seed longevity in storage have been improved so that they now take into account variations within a species in initial seed quality—which is affected by genotype and pre-storage environment—and so that they are more accurate over a wider range of storage environments These improvements have been incorporated into a seed viability nomograph for barley (Hordeum distichum L.) which may be used to predict percentage viabihty of any seed lot after any time in any storage environment within the range −20 to 90 °C and 5–25 per cent moisture content. Applications of the improved equations to seed drying and to long-term seed storage for genetic conservation are discussed.

Spring wheat ( Triticum aestivum L., ‘Chablis’) was grown under field conditions from sowing until harvest maturity, except for a 12-d period [70–82

Seeds of four cultivars of arabica coffee (Coffea arabica L.) were tested for germination following hermetic storage for up to 12 months at several different combinations of temperatures between −20 °C and 15 °C and moisture contents between 5% and 10% (wet basis). Most of the seeds from one cultivar withstood desiccation to between 5% and 6% moisture content, a seed water potential of approximately −250 MPa, but those of the remaining three cultivars were much more sensitive to desiccation damage. Moreover, in all four cultivars, seed longevity at cool and sub-zero temperatures, and at low moisture contents did not conform with orthodox seed storage behaviour: viability was lost more rapidly under these conditions than at either warmer temperatures or higher moisture contents. The results confirm that coffee seeds fail to satisfy the definitions of either typical orthodox or recalcitrant seed storage behaviour. These results, therefore, point to the possibility of a third category of storage behaviour intermediate between those of orthodox and recalcitrant seeds. One of the main features of this category is that dry seeds are injured by low temperatures.

For a single seed population of each of four species of grain legume positive linear relationships were shown between temperature and rate of germination for different fractions (G) of each population, from a base temperature, T_b(G), at which germination rate is zero, to an optimum temperature, T_o(G) at which germination rate is maximal. At constant temperatures warmer than T_o(G) there were negative relations (probably linear) between temperature and rate of germination to the maximum temperature for germination, T_m(G), Within each population T_b(G) did not differ, but it did vary between species, viz.0.0°C, 0.25°C, 4.and 8.5°C for chickpea (Cicer arietinum L.), lentil (Lens culinaris Medic.), soyabean (Glycine max [ Merr.) and cowpea (Vigna unguiculata [L.] Walp.), respectively. In contrast, T_o(G) varied both within each population and also between the four species: 80% of seeds in each population had T_o(G) values within the range 31.8°C to 33.8 °C, 24.0°C to 24.4°C, 34.0°C to 34.5°C and 33.2°C to >40°C, respectively. Values of T_m(G) were much more vanable: the 80% population range was 48 .0°C to 60.8°C for chickpea, 31.8°C to 34.4°C for lentil and 46.8°C to 55.2°C for soyabean; reliable estimates could not be made for cowpea, but the results suggest higher and more variable values of T_m(G) than in the other three species. At sub-optimal temperatures the distribution of thermal time for the different fractions of each population was normal, except for lentil where it was log-normal. A single equation is proposed to describe the influence of sub-optimal temperatures on rates of germination for whole seed populations. At supra-optimal temperatures, variation in thermal time for the different fractions of each population was only slight. The implications of these findings for the adaptation of grain legume crops to different environments, and for the screening of germplasm, are discussed.