Establishment growth in woody monocotyledons native to New Zealand

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Abstract
Larger monocotyledons without secondary thickening growth suffer mechanical and physiological deficiencies during early ontogeny which are over come by the development of an obconical axis during the establishment growth in the post-seedling phase of development. Diological specialisation commonly accompanies this phase. Larger monocotyledons native to New Zealand show an interesting range of adaptation to this establishment phase which relates to their adult habit. In three genera (Rhopalostylis, Freycentia, Ripogonum) the axis is produced entirely by primary growth. In the palm Rhopalostylis the seedling initially grows more or less vertically downward to a depth of about 20 cm and subsequently It turns through almost 180° and adopts its final. erect. position. The fre “saxophone” shape of the underground parts is very distinctive. In the axis is not self-supporting but develop into a root-climbmg liane with pronounced dimorphism of the aerial roots. The obconicaI stage of development is then very protracted. In Ripogomum the seedling axis remains underground. and increase to the adult size is largely the result of branching with successive branch orden of increasing size. The rhizome system is sympo dial with aerial axes of correspondingly increasing size. Cordyline species do produce secondary vascular tissues. The seedling axis undergoes gradual establishment growth to produce an obconical primary vascular cylinder which is supported by the secondary vascular system. Roots. however, lack thickening growth. In Cordyline australis and C. banksii the root-generating surface is largely provided by a lateral branch which Initiates a downwardly growing “vertical rhizome” which by means of ils secondary growth effectively functions as a “tap root”, although it is a stem. Attention is drawn to the differing ability of these plants to regenerate in the rost-seedling phase after damage.