Environmental control of flowering in some northern Carex species

Abstract

The environmental control of flowering in some arctic-alpine Carex species has been studied in controlled environments. Care x nigra, C. brunnescens, C. atrata, C. norwegica and C. serotina all had a dual induction requirement for flowering. In all except C. nigra either low temperature (12 °C or lower) or short days (SD) over a wider range of temperatures were needed for primary floral induction and inflorescence formation. In C. nigra primary floral induction took place in SD only (9-21 °C), 8-10 weeks of exposure being required for a full response. In all these species long days (LD) were required for, or strongly promoted, culm elongation and inflorescence development (secondary induction). Quantitative ecotype differences in both primary and secondary induction were demonstrated. Unlike the other species, C. bicolor proved to be a regular LD plant which required LD only for inflorescence initiation and development. In all species leaf growth was strongly promoted by LD, especially in the higher temperature range (15-21 °C). In SD and temperatures below 15 °C the leaves became senescent and the plants entered a semi-dormant condition which was immediately reversed by LD. The results are discussed in relation to growth form and life history of shoots.