Phyllotaxis diversity in Lycopodium clavatum L. and Lycopodium annotinum L.

Abstract

In shoots of Lycopodium microphyllous phyllotaxis is extremely diverse. 24 various patterns were found in anisotomous L. clavatum and "only" 11 in isotomous L. annotinum. Spiral patterns expressed by k:(k+1 ) parastichy numbers were present together with typically whorled k:k patterns. In both species k number was higher in plagiotropic shoots than in orthotropic. It was also higher in L. clavatum than in L. annotinum. In the first species phyllotactic spectrum was wider with many patterns almost equally frequent, whereas narrow spectrum of L. annotinum showed clear dominance of only one pattern. The patterns, which are the most frequent in other plants, such as Fibonacci or Lucas, were uncommon in studied Lycopodium species. Discontinuous phyllotactic transitions occurred typically in two locations on the shoot: just below the dichotomic branching or above the borders, that separate the annual increments of the axis. Transitions were moderately frequent occurring in more than 7% of developmentally independent shoot segments. Dichotomous branching, resulting in variable shoot diameter, seasonal fluctuations of growth as well as a small size of microphylls relative to the shoot circumference are proposed to be the main factors contributing to the high phyllotactic diversity in studied species.