Germination behaviour of the seeds of the New Zealand species Aristotelia serrata, Coprosma robusta, Cordyline australis, Myrtus obcordata, and Schefflera digitata

Abstract

Seeds from freshly collected fruit from two provenances each of Aristotelia serrata, Coprosma robusta, and Schefflera digitata and one each of Cordyline australis and Myrtus obcordata were tested in an unheated, partially shaded glasshouse in Christchurch, to discover germination rates, percentage germination success, and phenomena related to germination delay. The treatments were designed to simulate conditions that the seeds might experience after dispersal (normally after being consumed by birds). In the standard treatment (cleaned, moist, well-lit), from collections made in summer (Aristotelia) and autumn (the other four species), most of the seeds of each species germinated in late summer, or autumn — mid winter. A small proportion of Aristotelia and Cordyline seeds overwintered and germinated in the following spring. Overall success was high for all species (90–100%). Seeds of each species placed in the dark, or on soil, germinated at similar rates and with similar success but only for Cordyline were the rate and success as high as for the standard treatment. Seeds left in the fleshy pericarp tissues always germinated slowly and with low percentage success. A tetrazolium viability test was moderately reliable for Coprosma, Cordyline, and Myrtus seeds, but not for the other two species. The factors causing germination delay permit temporal spread of germination, but, even for Aristotelia and Cordyline, are insufficiently strong to permit development of long-term seed banks.

The habitat preferences of adult plants of the respective species can be explained in terms of their germination capabilities both in light and dark and also the degree of intolerance of their juveniles to shading.

Keywords:

• seeds
• fleshy fruit
• germination
• standard treatment
• high percentage success
• juveniles
• shade intolerance