Jm. Mjwara et al., PHOTOSYNTHESIS, GROWTH AND NUTRIENT CHANGES IN NONNODULATED PHASEOLUS-VULGARIS GROWN UNDER ATMOSPHERIC AND ELEVATED CARBON-DIOXIDE CONDITIONS, Physiologia Plantarum, 97(4), 1996, pp. 754-763
The response of Phaseolus vulgaris L. cv. Contender grown under contro
lled environment at either ambient or elevated (360 and 700 mu mol mol
(-1), respectively) CO2 concentrations ([CO2]), was monitored from 10
days after germination (DAG) until the onset of senescence. Elevated C
O2 had a pronounced effect on total plant height (TPH), leaf area (LA)
, leaf dry weight (LD), total plant biomass (TB) accumulation and spec
ific leaf area (SLA). All of these were significantly increased under
elevated carbon dioxide with the exception of SLA which was significan
tly reduced. Other than high initial growth rates in CO2-enriched plan
ts, relative growth rates remained relatively unchanged throughout the
growth period. While the trends in growth parameters were dearly diff
erent between [CO2], some physiological processes were largely transie
nt, in particular, net assimilation rate (NAR) and foliar nutrient con
centrations of N, Mg and Cu. CO2 enrichment significantly increased NA
R, but from 20 DAG, a steady decline to almost similar levels to those
measured in plants grown under ambient CO2 occurred. A similar trend
was observed for leaf N content where the loss of leaf nitrogen in CO2
-enriched plants after 20 DAG, was significantly greater than that obs
erved for ambient-CO2 plants. Under enhanced CO2, the foliar concentra
tions of K and Mn were increased significantly whilst P, Ca, Fe and Zn
were reduced significantly. Changes in Mg and Cu concentrations were
insignificant. In addition, high CO2 grown plants exhibited a pronounc
ed leaf discoloration or chlorosis, coupled with a significant reducti
on in leaf longevity.