To clarify the physiological responses and compare the resistance intensities of two Ardisias pecies to the treatments of cadmium stress

hydroponic experiment was carried out with 2 years old seedlings of Ardisia crenata Sims. and Ardisia mamillata Hance. In the experiment

the cadmium concentrations were designed as 0

0.025

0.05

0.1

0.2

and 0.4 mmol/L. Several physiological indicators including plant height

superoxide dismutase (SOD)

peroxidase (POD)

and catalase (CAT) activities

proline (Pro)

content malondialdehvde (MDA) content

photosynthetic characteristics

and fluorescence characteristics were measured. The following results were obtained: (1) Plant height

SOD

POD

and CAT activities of A. crenata and A. mamillata first increased with the increase of incubation time

and then the first two indicators decreased significantly; (2) After 20 days treatment

the accumulation of Pro content in the two plant species was induced for low cadmium concentration treatment (T2)

especially significant for A. mamillata

which was up to 149.24%; (3) After 20 days treatment

MDA contents increased

with the highest increases of 169.07% and 122.70%

respectively; (4) An obvious increase of photosynthetic electron transfer efficiency (ETR) of A. mamillata was observed for low cadmium concentration treatment (T2)

while qP (photochemical quenching coefficient) had no significant change

indicating that A. crenata startes the energy dissipation pathways sufficiently to avoid the damage of photosynthetic mechanism; (5) Both ETR and qP of A. mamillata decreased significantly after treatment with high concentration of cadmium (T4)

indicating that PSII of A. mamillata has been hurt under the high concentrations of cadmium stress with the increasing of SOD and the damage of chloroplast structure; (6) ETR fluorescence parameters of A. crenata descended even in early stage of cadmium stress

and the decrease was much more significant in the later stage. After comprehensive analyses

it is supposed that both A. crenata and A. mamillata increase their antioxidant enzyme activities to resist stress for treatments with low cadmium concentrations

whereas high concentrations of cadmium destroye antioxidant enzyme and photosynthetical systems and thus decrease plant resistance. It is found that A. mamillata had higher resistance to cadmium than Ardisia crenata Sims

and has high potential for cultivation under the environment with high concentrations of cadmium.