Physiological acclimation of seashore paspalum and bermudagrass to low light

Physiological responses play an important role in low light tolerance in plants. The acclimations of photosynthetic activities, total soluble protein, and antioxidant enzyme were characterized in low light-tolerant 'Sea Isle 1' seashore paspalum (Paspalum vaginatum Swartz) and intolerant 'TifSport' hybrid bermudagrass (Cynodon dactylon L. x Cynodon transvaalensis Burtt-Davy) grown under high light control (HL, 500-900 mu mol m(-2) s (-1)),low light (LL, 60-100 mu mol m(-2) s(-1)), and LL to HL transfer in the greenhouse. Shade cloth was used to create the LL treatment. Sea Isle I maintained higher turf quality and normalized difference vegetation index (NDVI) than that of TifSport under LL. Chlorophyll a (Chl a) and chlorophyll b (Chl b) content were reduced by 34-36% in Sea Isle I and by 51-63% in TifSport at day 35 of LL, respectively, relative to their HL levels. Chlorophyll a[b ratio (Chl a/b) generally was not affected by LL for Sea Isle 1, but the values under LL increased to above HL level in TifSport. Photochemical efficiency (Fv/Fm) remained constant under LL in both species. Total soluble protein content (SPC), water-soluble carbohydrate content (WSC), catalase (CAT) activity, and ascorbate peroxidase (APX) activity decreased 22% and 55%, 52% and 66%, 68% and 77%, and 40% and 66% under LL for Sea Isle I and TifSport, respectively. After grasses were transferred from LL to HL, Chl a, Chl b, SPC, WSC, and CAT activity increased, but to a higher extent in Sea Isle 1. A short-term reduction in Fv/Fm was exhibited in both species after light transfer but a further decrease was found in TifSport. The results indicated that the relative higher levels of Chl, SPC, WSC, and antioxidant enzyme activities under LL contributed to better LL tolerance in grass species. More rapid recovery of these parameters from LL to HL was a characteristic of the tolerant Sea Isle 1 seashore paspalum relative to the intolerant TifSport bermudagrass. (c) 2004 Elsevier B.V. All rights reserved.