Germination behaviour of the seeds of seven New Zealand vine species
New Zealand Journal of Botany
Germination rates, percentage germination success, and phenomena related to germination delay were determined for seeds from freshly collected fruit (summer-autumn) of Calystegia tuguriorum, Clematis foetida, Muehlenbeckia australis, Parsonsia heterophylla, Ripogonum scandens, Rubus cissoides, and Tetrapathaea tetrandra. The experimental treatments simulated natural conditions that the seeds might experience after dispersal. In the standard treatment (seeds cleaned, moist, well-lit) seeds of each species behaved differently. Ripogonum seeds germinated through autumn and winter; in late-collected fruit some had germinated viviparously. The large seeds have a very thin testa and are killed by drying. Some Muehlenbeckia seeds germinated in autumn, the rest did not do so until early spring. Clematis and Tetrapathaea seeds did not start germinating until late winter (when temperatures were rising) and all viable seeds had germinated within two months. A few Rubus and Parsonsia seeds germinated, respectively, in autumn and spring. Germination of the remaining seeds occurred at a slow, steady rate for Rubus, for two years, and during warm periods for Parsonsia, for three years. Sporadic germination of hard-coated Calystegia seeds occurred over five years. The amount of germination success was high (89-98%) for Clematis, Ripogonum, Muehlenbeckia, and Tetrapathaea, but only 18, 73, and 82%, respectively, for Calystegia, Parsonsia, and Rubus. In the dark treatment most Tetrapathaea and Parsonsia seeds germinated, but only moderate numbers of Ripogonum, Muehlenbeckia, and Rubus seeds and none of Clematis. In the soil treatment germination success was lower than in the standard treatment and germination rates were slower. The same applied to seeds in the in-fruit treatment for Muehlenbeckia, Parsonsia, and Rubus. No radicles emerged in the in-fruit treatment for Ripogonum, but the embryos of many developed, viviparously, to the immediate pre-emergence stage. Ripogonum, Calystegia, Clematis, Muehlenbeckia, and Tetrapathaea can all maintain short-term seed banks, in fruit, on the parents (for two months or more). Rubus, Parsonsia, and Calystegia seeds can persist in soil seed banks for more than a year. Ripogonum does not maintain soil seed banks. It is not known whether seeds of Clematis and Tetrapathaea can do so. Generally the seed germination phenomena accord well with the habitat preferences of the respective species.