Growth and net photosynthetic rates of Hosta ‘blue vision’ during acclimatization in bright, natural light with CO2 enrichment

Abstract

Hosta ‘Blue Vision’, a shade-adapted perennial, was successfully acclimatized in high, natural light conditions in the research AcclimatronTM at Clemson University, Clemson, SC during the summer of 2000. The supplemental CO2 levels achieved during acclimatization were 710±113, 2396±121, and 5641±119 μmol mol−1, approximately 2×, 6×, and 15× ambient CO2. Plants were maintained in H2O-saturated atmospheres and protected from temperature increases associated with high light intensity. In the 5 wk following ex vitro transfer, plantlet roots grew at the 2× CO2 level, but shoot biomass was unaffected. Results for the 6× and 15× CO2 levels were comparable and provided the best plantlet growth. The “doubling time’ that is characteristic of exponential growth was 10.8 and 9.8 d for root and shoot dry weights, respectively. There was no indication of light saturation of net photosynthetic rate (NPR) over the photosynthetic photon flux density (PPFD) range of 100–1200 μmolm−2s−1 experienced during this study. An interaction between CO2 and light intensity levels was detected for NPR of Hosta ‘Blue Vision’ with CO2 saturation occurring at approximately 2800 μmol mol−1. regardless of light level. Furthermore, at the optimal CO2 level, NPR increased quadratically as light intensity increased, and NPR was greatest at the maximum light intensity (PPFD: 1200 μmol m−2s−1).