TITLE:
The Effect of Wide-Range Photosynthetic Active Radiations on Photosynthesis, Growth and Flowering of Rosa sp. and Kalanchoe blossfeldiana
AUTHORS:
Leiv M. Mortensen
KEYWORDS:
Ait Temperature, Carbon Dioxide Exchange Rate, Flowering, Growth, Kalanchoe blossfeldiana, Miniature Rose, Photon Flux Density, Photosynthetic Active Radiation
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.11,
May
14,
2014
ABSTRACT: Miniature
roses (Rosa sp.) and Kalanchoe blossfeldiana were grown at photon flux
densities (PFD) ranging from 60 to 670 μmol·m-2·s-1 (associated with a temperature gradient from 20.0°C to 24.0°C [TEMP1]) and from
50 to 370μmol·m-2-s-1 (associated with a temperature gradient from 22.5°C to 26.5°C [TEMP2]).
The experiment was conducted in a greenhouse compartment at latitude 59° north
in mid-winter. The daily photosynthetic active radiations (PAR) ranged from 4.3
to 48.2 and 3.6 to 26.6 mol·m-2·day-1 in the TEMP1 and
TEMP2 treatments, respectively. Time until flowering in miniature roses
decreased from about 50 to 35 days in the TEMP1 treatment and from 50 to 25
days in the TEMP2 treatment, when the PFD increased from 50 to 370μmol·m-2·s-1. In Kalanchoe
time until flowering was decreased to the same extent (about 15 days) in both
temperature treatments when PFD increased from 50 to 370 μmol·m-2·s-1. The
number of flowers and the plant dry weight in miniature roses increased up to
300 – 400 μmol·m-2·s-1 PFD (21.6 - 28.8 mol·m-2 day-1 PAR), while flower stem
fresh weight and plant dry weight in Kalanchoe increased up to 200 – 300 μmol·m-2·s-1 at TEMP1.
Measurements of the diurnal carbon dioxide exchange rates (CER) in daylight in
small plant stands of roses in summertime showed that CER was saturated at
about 300 μmol·m-2·s-1 PFD at 370 μmol·mol-1 CO2 and at 400 – 500 μmol·m-2·s-1 PFD at 800
μmol·mol-1 CO2. For Kalanchoe similar results were
obtained. Increasing the CO2 concentration from 370 to 800 μmol·mol-1 increased the CER in roses (48%) as well in Kalanchoe (69%). It was concluded
that 15 to 20 mol·m-2·day-1 combined with about 24°C air
temperature and high CO2 concentration will give a very good growth
with lot of flowers within a short production time in miniature roses. For Kalanchoe 10 to 15 mol·m-2·day-1 combined with about 20°C and high CO2 produced a similar result.