Kinetin is an important growth hormone used for in vitro propagation, but its dynamic and temporal effects on Dioscoreaalata have not been thoroughly evaluated. In this study, surface response models were developed to...Kinetin is an important growth hormone used for in vitro propagation, but its dynamic and temporal effects on Dioscoreaalata have not been thoroughly evaluated. In this study, surface response models were developed to better elucidate the effects ofkinetin on D. alata propagated in vitro. Nodal segments were obtained from Akaaba, an important D. alata cultivar in Ghana, andpropagated in vitro under five kinetin rates （0, 2.5, 5, 7.5 and 10 μM）. The models were developed using segmented multipleregression with time and kinetin as the predictors. The effects on plant height, the number of leaves, shoots and roots were assessedwith three-dimensional figures for better observation of temporal trends. The model fit was very good with normalized root meansquared error （NRMSE） = 0.1, R-squared = 0.83 and adjusted R-squared = 0.82, averaged across the different growth parameters.Different kinetin levels elicited the maximum shoot, leaf and root formation, as well as the growth rates over time. Moderate kinetinlevels （2-4 μM） provided better growth at early culturing period. Higher kinetin levels （5-10 μM） suppressed the growth of theplantlets at early stages, but the plantlets recovered from the stress and resumed normal growth thereafter. After 4-5 weeks, thegrowth rates of the moderate kinetin levels （2-4 μM） declined much faster and were lower compared to the higher kinetin levels,except plant height and the number of roots which were still higher at the moderate kinetin level even after eight weeks of culturing.Thus, kinetin requirements vary depending on the growth parameters of interest.展开更多
The results observed in the literature raise the hypothesis according to which cytokinin plays important roles in photosynthetic metabolisms and antioxidant enzymes. Thus, the study aimed to evaluate the effect of fol...The results observed in the literature raise the hypothesis according to which cytokinin plays important roles in photosynthetic metabolisms and antioxidant enzymes. Thus, the study aimed to evaluate the effect of foliar application of the isolated cytokinin kinetin at the production cycle, seeking to analyze its effects on enzyme activity and photosynthetic parameters. The plants treated with CK presented reduction of leaf CO_2 assimilation rate(Pn) and stomatal conductance(Gs), while that transpiration rate(Tr) was unaffected. The internal CO_2 concentrations decreased with the increase in cytokinin levels, but were maintained under CK 50 mg·L^(-1). The plants treated with CK 75 mg·L^(-1) was verified higher carboxylation efficiency(Pn/Ci), which was associated to values of CO_2 assimilation and transpiration unaltered. Apparent electron transport rate showed variations in the concentration of 25 mg·L^(-1). Considering the study of enzyme activity, on the other hand, it cannot be stated that kinetin has an effective action in delaying oxidative damage. It presents mixed results, since an efficiency in the application of cytokinin was not observed, presenting induction levels of ascorbate peroxidase activity. Thus, further research is needed to determine more precisely the effects of kinetin on gas exchange and antioxidant enzymes in anthurium plants.展开更多
文摘Kinetin is an important growth hormone used for in vitro propagation, but its dynamic and temporal effects on Dioscoreaalata have not been thoroughly evaluated. In this study, surface response models were developed to better elucidate the effects ofkinetin on D. alata propagated in vitro. Nodal segments were obtained from Akaaba, an important D. alata cultivar in Ghana, andpropagated in vitro under five kinetin rates （0, 2.5, 5, 7.5 and 10 μM）. The models were developed using segmented multipleregression with time and kinetin as the predictors. The effects on plant height, the number of leaves, shoots and roots were assessedwith three-dimensional figures for better observation of temporal trends. The model fit was very good with normalized root meansquared error （NRMSE） = 0.1, R-squared = 0.83 and adjusted R-squared = 0.82, averaged across the different growth parameters.Different kinetin levels elicited the maximum shoot, leaf and root formation, as well as the growth rates over time. Moderate kinetinlevels （2-4 μM） provided better growth at early culturing period. Higher kinetin levels （5-10 μM） suppressed the growth of theplantlets at early stages, but the plantlets recovered from the stress and resumed normal growth thereafter. After 4-5 weeks, thegrowth rates of the moderate kinetin levels （2-4 μM） declined much faster and were lower compared to the higher kinetin levels,except plant height and the number of roots which were still higher at the moderate kinetin level even after eight weeks of culturing.Thus, kinetin requirements vary depending on the growth parameters of interest.
基金National Counsel of Technological and Scientific Developmen-CNPq and Fundacao de Amparo a Ciencia e Tecnologia de Pernambuco(FACEPE/DCR-0093-5.01/13:APQ-0053-5.01/14 and APQ-0532-5.01/14)for the financial support to this work
文摘The results observed in the literature raise the hypothesis according to which cytokinin plays important roles in photosynthetic metabolisms and antioxidant enzymes. Thus, the study aimed to evaluate the effect of foliar application of the isolated cytokinin kinetin at the production cycle, seeking to analyze its effects on enzyme activity and photosynthetic parameters. The plants treated with CK presented reduction of leaf CO_2 assimilation rate(Pn) and stomatal conductance(Gs), while that transpiration rate(Tr) was unaffected. The internal CO_2 concentrations decreased with the increase in cytokinin levels, but were maintained under CK 50 mg·L^(-1). The plants treated with CK 75 mg·L^(-1) was verified higher carboxylation efficiency(Pn/Ci), which was associated to values of CO_2 assimilation and transpiration unaltered. Apparent electron transport rate showed variations in the concentration of 25 mg·L^(-1). Considering the study of enzyme activity, on the other hand, it cannot be stated that kinetin has an effective action in delaying oxidative damage. It presents mixed results, since an efficiency in the application of cytokinin was not observed, presenting induction levels of ascorbate peroxidase activity. Thus, further research is needed to determine more precisely the effects of kinetin on gas exchange and antioxidant enzymes in anthurium plants.
