This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and...This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and assimilation of lettuce plants at different root-zone temperatures (RZT). Elevated RZ [CO<sub>2</sub>] stimulated root development, root and shoot growth compared to ambient RZ [CO<sub>2</sub>]. The greatest increase in root growth was observed in plants grown under elevated RZ [CO<sub>2</sub>] of 50,000 ppm. However, RZ [CO<sub>2</sub>] of 10,000 ppm was sufficient to achieve the maximal leaf area and shoot productivity. Lettuce plants exhibited faster shoot and root growth at 20°C-RZT than at ambient (A)-RZT. However, under elevated RZ [CO<sub>2</sub>], the magnitude of increased growth was greater at A-RZT than at 20°C-RZT. Compared to RZ [CO<sub>2</sub>] of 360 ppm, elevated RZ [CO<sub>2</sub>] of 10,000 ppm increased NO<sub>3</sub>-</sup> accumulation and nitrate reductase activity (NRA) in both leaves and roots. NO<sub>3</sub>-</sup> concentrations of leaf and root were higher at 20°C-RZT than at A-RZT in all plants. NRA was higher in root than in leaf especially under A-RZT. The total reduced nitrogen (TRN) concentration was significantly higher in plants grown under elevated RZ [CO<sub>2</sub>] of 10,000 ppm than under ambient RZ [CO<sub>2</sub>] of 360 ppm with greater concentration in 20°C-RZT plants than in A-RZT plants. These results imply that elevated RZ [CO<sub>2</sub>] significantly affected root morphology, root and shoot growth and N metabolism of temperate lettuce with greater impacts at A-RZT than at 20°C-RZT. These findings have practical significance to vegetable production by growing the vegetable crops at cool-RZT with elevated RZ [CO<sub>2</sub>] to enhance its productivity.展开更多
Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its ro...Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its root-zone. In this paper, a cool Meditteranean vegetable, Eruca sativa, was studied to understand how different RZTs can impact its shoot productivity, photosynthesis and nutritional quality. All plants were cultivated using aeroponic systems in a tropical greenhouse under hot ambient conditions where roots were subjected to four different root-zone temperatures (RZTs) of 20°C-RZT, 25°C-RZT, 30°C-RZT and fluctuating ambient temperatures ranged from 25°C to 38°C [25°C/38°C (ambient)]-RZT. Parameters studied include shoot fresh weight (FW), photosynthetic gas exchange, midday chlorophyll (Chl) fluorescence F<sub>v</sub>/F<sub>m</sub> ratio, Chl fluorescence photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate (ETR), total phenolic compounds and mineral content such as potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe). Among the 4 different RZT treatments, E. sativa plants grown under ambient-RZT (25/38°C-RZT) had the lowest shoot and root FW while those plants grown under 20°C-RZT had highest productivity of shoot and root. However, there were no significant differences in shoot and root FW in plants grown at 25°C- and 30°C-RZT. Compared to plants grown under 25°C/38°C (ambient-RZT), light-saturated photosynthetic CO<sub>2</sub> assimilation rate (A<sub>sat</sub>) and stomatal conductance (g<sub>ssat</sub>) were similarly higher in 20°C-, 25°C- and 30°C-RZT. All plants had midday Chl fluorescence F<sub>v</sub>/F<sub>m</sub> ratio lower than <0.8 ranged from 0.785 to 0.606 with the highest and lowest ratios recorded in 20°C-RZT and ambient-RZT plants, respectively. These results indicate that cooling the RZ of E. sativa plants protected their PS II from photoinactivation during midday in the greenhouse. There were no significant differences observed in photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate among plants grown under 20°C-, 25°C- and 30°C-RZT. However, plants grown under ambient-RZT had lower qP, qN and ETR compared to all other plants. E. sativa at 20°C-RZT with the best developed roots had the highest dietary mineral (K, Mg, Ca and Fe) contents but lower total phenolics content. In contrast, ambient-RZT, plants with poorly developed roots had the lowest mineral content but highest total phenolic content. The results of this study suggest that cooling of roots is a feasible method for the cultivation of E. sativa in the tropic, which enhances the content of dietary minerals in shoots.展开更多
Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology. A comprehensive knowledge of the distribution and movement of soil water in root zone is ess...Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology. A comprehensive knowledge of the distribution and movement of soil water in root zone is essential for the design and management of irrigation regimes. Simulation models have been proved to be efficient methods for this purpose. In this study, the numerical model Hydrus-2D was used to simulate the temporal variations of soil water content in a drip irrigated cotton field under mulching. A concept of partitioning coefficient, calibrated to be 0.07, was introduced to describe the effect of plastic mulch on prevention of evaporation. The soil hydraulic parameters were optimized by inverse solution using the field data. At the optimized conditions, the model was used to predict soil water content for four field treatments. The agreements between the predictions and observations were evaluated using coefficient of determination （R2） and root mean square error （RMSE）. The results suggested that the model fairly reproduced the variations in soil water content at all locations in four treatments, with R2 ranging from 0.582 to 0.826 and RMSE from 0.029 to 0.050 cm3 cm-3, indicating that the simulations agreed well with the observations.展开更多
文摘This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and assimilation of lettuce plants at different root-zone temperatures (RZT). Elevated RZ [CO<sub>2</sub>] stimulated root development, root and shoot growth compared to ambient RZ [CO<sub>2</sub>]. The greatest increase in root growth was observed in plants grown under elevated RZ [CO<sub>2</sub>] of 50,000 ppm. However, RZ [CO<sub>2</sub>] of 10,000 ppm was sufficient to achieve the maximal leaf area and shoot productivity. Lettuce plants exhibited faster shoot and root growth at 20°C-RZT than at ambient (A)-RZT. However, under elevated RZ [CO<sub>2</sub>], the magnitude of increased growth was greater at A-RZT than at 20°C-RZT. Compared to RZ [CO<sub>2</sub>] of 360 ppm, elevated RZ [CO<sub>2</sub>] of 10,000 ppm increased NO<sub>3</sub>-</sup> accumulation and nitrate reductase activity (NRA) in both leaves and roots. NO<sub>3</sub>-</sup> concentrations of leaf and root were higher at 20°C-RZT than at A-RZT in all plants. NRA was higher in root than in leaf especially under A-RZT. The total reduced nitrogen (TRN) concentration was significantly higher in plants grown under elevated RZ [CO<sub>2</sub>] of 10,000 ppm than under ambient RZ [CO<sub>2</sub>] of 360 ppm with greater concentration in 20°C-RZT plants than in A-RZT plants. These results imply that elevated RZ [CO<sub>2</sub>] significantly affected root morphology, root and shoot growth and N metabolism of temperate lettuce with greater impacts at A-RZT than at 20°C-RZT. These findings have practical significance to vegetable production by growing the vegetable crops at cool-RZT with elevated RZ [CO<sub>2</sub>] to enhance its productivity.
文摘Although tropical high ambient temperature and humidity severely reduced the productivity of temperate plants, temperate vegetable crops such as lettuce have been successfully grown in Singapore by only cooling its root-zone. In this paper, a cool Meditteranean vegetable, Eruca sativa, was studied to understand how different RZTs can impact its shoot productivity, photosynthesis and nutritional quality. All plants were cultivated using aeroponic systems in a tropical greenhouse under hot ambient conditions where roots were subjected to four different root-zone temperatures (RZTs) of 20°C-RZT, 25°C-RZT, 30°C-RZT and fluctuating ambient temperatures ranged from 25°C to 38°C [25°C/38°C (ambient)]-RZT. Parameters studied include shoot fresh weight (FW), photosynthetic gas exchange, midday chlorophyll (Chl) fluorescence F<sub>v</sub>/F<sub>m</sub> ratio, Chl fluorescence photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate (ETR), total phenolic compounds and mineral content such as potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe). Among the 4 different RZT treatments, E. sativa plants grown under ambient-RZT (25/38°C-RZT) had the lowest shoot and root FW while those plants grown under 20°C-RZT had highest productivity of shoot and root. However, there were no significant differences in shoot and root FW in plants grown at 25°C- and 30°C-RZT. Compared to plants grown under 25°C/38°C (ambient-RZT), light-saturated photosynthetic CO<sub>2</sub> assimilation rate (A<sub>sat</sub>) and stomatal conductance (g<sub>ssat</sub>) were similarly higher in 20°C-, 25°C- and 30°C-RZT. All plants had midday Chl fluorescence F<sub>v</sub>/F<sub>m</sub> ratio lower than <0.8 ranged from 0.785 to 0.606 with the highest and lowest ratios recorded in 20°C-RZT and ambient-RZT plants, respectively. These results indicate that cooling the RZ of E. sativa plants protected their PS II from photoinactivation during midday in the greenhouse. There were no significant differences observed in photochemical quenching (qP), non-photochemical quenching (qN) and electron transport rate among plants grown under 20°C-, 25°C- and 30°C-RZT. However, plants grown under ambient-RZT had lower qP, qN and ETR compared to all other plants. E. sativa at 20°C-RZT with the best developed roots had the highest dietary mineral (K, Mg, Ca and Fe) contents but lower total phenolics content. In contrast, ambient-RZT, plants with poorly developed roots had the lowest mineral content but highest total phenolic content. The results of this study suggest that cooling of roots is a feasible method for the cultivation of E. sativa in the tropic, which enhances the content of dietary minerals in shoots.
基金Supported by the Special Fund of Industrial(Agriculture) Research for Public Welfare of China(No.200903001)the Special Fund of Industrial(Marine) Research for Public Welfare of China(Nos.201105020-3 and 201105020-4)+2 种基金the Jiangsu Provincial Science and Technology Support Program,China(No.BE2010313)the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KZCX2-YW-359)the National Natural Science Foundation of China(No.41171181)
文摘Drip irrigation under plastic mulch has been widely applied in arid Northwest China as a water-saving irrigation technology. A comprehensive knowledge of the distribution and movement of soil water in root zone is essential for the design and management of irrigation regimes. Simulation models have been proved to be efficient methods for this purpose. In this study, the numerical model Hydrus-2D was used to simulate the temporal variations of soil water content in a drip irrigated cotton field under mulching. A concept of partitioning coefficient, calibrated to be 0.07, was introduced to describe the effect of plastic mulch on prevention of evaporation. The soil hydraulic parameters were optimized by inverse solution using the field data. At the optimized conditions, the model was used to predict soil water content for four field treatments. The agreements between the predictions and observations were evaluated using coefficient of determination （R2） and root mean square error （RMSE）. The results suggested that the model fairly reproduced the variations in soil water content at all locations in four treatments, with R2 ranging from 0.582 to 0.826 and RMSE from 0.029 to 0.050 cm3 cm-3, indicating that the simulations agreed well with the observations.
