REGULATION OF GERMINATION OF SEED OF ANIGOZANTHOS-MANGLESII

Germination of seed of Anigozanthos (Haemodoraceae) species is usually low and unreliable which hinders the propagation of sexually generate d progeny, impedes plant breeding activities and their use in horticul ture. This study was undertaken to investigate the basis of these germ ination problems. Seeds of cultivated Anigozanthos manglesii D. Don. w ere shown to possess two mechanisms for regulating seed germination, b oth of which were external to the embryo. Embryos germinated freely on excision and culture on nutrient agar. This first barrier is a physic o-chemical barrier and can be eliminated by a brief treatment with 5 M KOH and less effectively by physical abrasion with 50% H2SO4 or 0.7% NaOCl. Release of this barrier was correlated with permeability to flu orescein diacetate (FDA) and this proved to be a more useful indicator of seed viability than 2,3,5-triphenyl tetrazolium chloride (TTC). Th e other barrier was physiological and could be eliminated by treatment with GA(3) or KNO3. Treatment of A, viridis Endl., A. humilis Lindley and A, flavidus DC. with KOH or H2SO2 with or without GA(3) elicited a small, a nil or negative response showing that mechanisms of control of germination may differ between taxa. Observations on the effects o f temperature and duration of storage suggest mechanisms which may be significant in natural systems: moist stratification at 5 degrees C ca used reduced germination but sustained viability (as assessed by FDA) while dry seed stored at room temperature, showed increased germinatio n with increasing duration of storage. The chilling response may indic ate the capacity to initiate secondary dormancy under unfavourable ger mination conditions.