Now showing 1 - 10 of 34
  • Publication
    Open Access
    Growth and photosynthetic characteristic of sweet potato (Ipomoea batatas) leaves grown under natural sunlight with supplement LED lighting in a tropical greenhouse
    (2020) ;
    Qin, Lin
    Leaf growth and photosynthetic characteristics of sweet potato (Ipomoea batatas var. Biru Putih) grown under different light quantities were studied in a tropical greenhouse. The stem cuttings of I. batataswith adventitious roots were grown hydroponically under (1) only natural sunlight (SL); (2) SL with supplemental LED at a PPFD of 150 μmol m−2 s–1 (SL + L-LED); and (3) SL with supplemental LED at a PPFD of 300 μmol m−2 s–1 (SL + H-LED). One week after emergence, all leaves had similar area and water content. However, leaf fresh weight and dry weight were significantly higher in plants grown under SL+L-LED and SL + H-LED than under SL due to their thicker leaves reflected by the lower specific leaf area. Plants grown under SL had significantly lower concentrations of total chlorophyll (Chl) and total carotenoids (Car) but higher Chl a/b ratio than under SL + L-LED and SL + H-LED. However, all plants had similar Chl/Car ratios. Although midday Fv/Fm ratio was the lowest in leaves grown under SL+ H-LED followed by SL + L-LED and SL, predawn Fv/Fm ratios of all leaves were higher than 0.8. Increasing growth irradiance with supplemental LED resulted in higher electron transport rate and photochemical quenching but lower non-photochemical quenching compared to those of plants grown under SL. Measured under their respective growth irradiance in the greenhouse, attached leaves grown under SL + L-LED and SL+H-LED had significantly higher photosynthetic CO2 assimilation rate and stomatal conductance than under SL. However, measuring the detached leaves at 25 °C in the laboratory, there were no significant differences in PS II and Cyt b6f concentrations although light- and CO2-statured photosynthetic O2 evolution rates were slightly higher in leaves grown under SL+ H-LED than under SL. Impacts of supplemental LED on leaf growth and photosynthetic characteristics were discussed.
    WOS© Citations 17Scopus© Citations 20  47  65
  • Publication
    Open Access
    A general best-fitting equation for the multimodal soil-water characteristic curve
    (2023)
    Zhao, Yan
    ;
    Harianto Rahardjo
    ;
    Satyanaga, Alfrendo
    ;
    Zhai, Qian
    ;
    The soil–water characteristic curve (SWCC) is one of the most crucial and fundamental soil properties in unsaturated soil mechanics. Many theories and equations have been developed to describe and best fit SWCC with unimodal or bimodal characteristics. In this study, a general best-fitting equation for SWCC with multimodal characteristics (bimodal and trimodal SWCC) is proposed. The parameters in the proposed equation are closely related to the properties of soil and variables in the SWCC. To evaluate the performance of the proposed equation in best-fitting multimodal SWCC that has more than two modalities, a trimodal SWCC soil mixture that consists of sand, kaolin and activated carbon has been prepared and tested in the laboratory in this study. The proposed equation has been evaluated with data from published literature and the newly developed soil mixture of trimodal SWCC. The proposed equation has shown high accuracy for best-fitting bimodal SWCC and trimodal SWCC.
    WOS© Citations 6Scopus© Citations 7  64  3
  • Publication
    Open Access
    Root-zone heat priming effects on maximum quantum efficiency of PSII, productivity, root morphology and nutritional quality of two aeroponically grown leafy greens in a tropical greenhouse
    (2022) ;
    Tan, Cassander
    ;
    Qin, Lin
    This study investigated the effects of root zone (RZ) heat priming on Eruca sativa (cv. Arugula) and Lactuca sativa (cv. Canasta) in a tropical greenhouse by exposing them to three different RZ temperatures (RZTs). For the first group, plants were grown at 25 °C-RZT for 36 days. The second group of plants was grown at 25 °C-RZT for 10 days before transferring to 38 °C-RZT for 10 days and then to 42 °C-RZT for another 16 days (primed). For the third group, plants were grown at 25 °C-RZT for 20 days and for the last 16 days were transferred to 42 °C-RZT (non-primed). RZ heat priming did not affect the leaf expansion of Arugula while the leaf expansion was slower in RZ heat primed Canasta compared to 25 °C-RZT plants. After transferring to 42 °C-RZT in the later stage, RZ heat primed Arugula had similar productivity but a larger root system with higher nutritional quality at harvest and during postharvest storage compared to those of 25 °C-RZT plants. After subjection to 42 °C-RZT, although RZ heat priming enhanced its nutritional quality, the productivity of Canasta was compromised. The results of this study suggest that it is feasible to enhance productivity and nutritional quality of leafy greens at lower production cost through RZT management.
    WOS© Citations 2Scopus© Citations 3  180  47
  • Publication
    Open Access
    LED spectral quality and NaCl salinity interact to affect growth, photosynthesis and phytochemical production of Mesembryanthemum crystallinum
    (2021) ;
    Koh, Dominic Jing Qun
    ;
    Qin, Lin
    The edible halophyte Mesembryanthemum crystallinum L. was grown at different NaCl salinities under different combined red and blue light-emitting diode (LED) light treatments. High salinity (500 mM NaCl) decreased biomass, leaf growth, and leaf water content. Interactions between LED ratio and salinity were detected for shoot biomass and leaf growth. All plants had Fv/Fm ratios close to 0.8 in dark-adapted leaves, suggesting that they were all healthy with similar maximal efficiency of PSII photochemistry. However, measured under the actinic light near or above the growth light, the electron transport rate (ETR) and photochemical quenching (qP) of M. crystallinum grown at 100 and 250 mM NaCl were higher than at 500 mM NaCl. Grown under red/blue LED ratios of 0.9, M. crystallinum had higher ETR and qP across all salinities indicating higher light energy utilisation. Crassulacean acid metabolism (CAM) was induced in M. crystallinum grown at 500 mM NaCl. CAM-induced leaves had much higher non-photochemical quenching (NPQ), suggesting that NPQ can be used to estimate CAM induction. M. crystallinum grown at 250 and 500 mM NaCl had higher total chlorophyll and carotenoids contents than at 100 mM NaCl. Proline, total soluble sugar, ascorbic acid, and total phenolic compounds were higher in plants at 250 and 500 mM NaCl compared with those at 100 mM NaCl. An interaction between LED ratio and salinity was detected for proline content. Findings of this study suggest that both salinity and light quality affect productivity, photosynthetic light use efficiency, and proline accumulation of M. crystallinum.
    WOS© Citations 16Scopus© Citations 16  291  56
  • Publication
    Open Access
    Effects of short light/dark cycles on photosynthetic pathway switching and growth of medicinal Dendrobium officinale in aeroponic cultivation
    (2019)
    Cheng, Yongsan
    ;
    He, Dongxian
    ;
    ;
    Niu, Genhua
    ;
    Ji, Fang
    Dendrobium officinale has high medicinal value but grows slowly in natural environment due to its special CAM photosynthetic pathway. In this study, D. officinale were grown aeroponically with light/dark cycles of 12 h/12 h, 4 h/4 h, and 2 h/2 h for 150 d. The photosynthetic electron transfer characteristics, photosynthetic CO2 fixation pathways, and accumulations of biomass and soluble polysaccharides in D. officinale leaves were studied. The results showed that the photosynthetic apparatus states of D. officinale in aeroponic cultivation under short light/dark cycles of 4 h/4 h and 2 h/2 h were better than that under 12 h/12 h. The dark net CO2 exchange percentages of D. officinale were negative in short light/dark cycles of 4 h/4 h and 2 h/2 h, and the daily net CO2 exchange amount and dry/fresh weight increases were doubled compared with those in 12 h/12 h light/dark cycle. High soluble polysaccharides content and the soluble polysaccharides yield of D. officinale were obtained in the shorter light/dark cycle of 2 h/2 h. Therefore, the photosynthetic pathway of D. officinale could be switched from CAM to C3 by short light/dark cycles of 4 h/4 h and 2 h/2 h, and its higher biomass accumulation and soluble polysaccharides yield could be obtained by the shorter light/dark cycle of 2 h/2 h in aeroponic cultivation.
    WOS© Citations 2  211  68
  • Publication
    Open Access
    Impacts of reduced nitrate supply on nitrogen metabolism, photosynthetic light-use efficiency, and nutritional values of edible mesembryanthemum crystallinum
    (2021) ;
    Qin, Lin
    Mesembryanthemum crystallinum (common ice plant), as a nutritious ready-to-eat salad in Singapore, has become popular in recent years. However, basic data about the impacts of NO₃⁻ supply on its NO₃⁻ accumulation and nutritional quality are lacking. In this study, all plants were first grown indoor hydroponically in 10% artificial seawater (ASW) with modified full-strength Netherlands Standard Composition nutrient solution for 11 days, before transferring them to different reduced NO₃⁻ solutions. All plants grew well and healthy after 7 days of treatment. However, plants grown with 3/4 N and 1/2 N were bigger with higher shoot and root fresh weight (FW), greater leaf number, and total leaf area (TLA) than those grown with full nitrogen (N), 1/4 N, and 0 N. Mesembryanthemum crystallinum grown with full N, 3/4 N, and 1/4 N had similar specific leaf area (SLA), while 0 N plants had significantly lower SLA. All plants had similar leaf succulence (LS). However, leaf water content (LWC) was lower, while leaf dry matter accumulation (LDMC) was higher in 0 N plants after 7 days of treatment. Compared with plants grown with full N, shoot NO₃⁻ concentrations in 3/4 N, 1/2 N, and 1/4 N plants were constant or slightly increased during the treatments. For 0 N plants, shoot NO₃⁻ concentration decreased significantly during the treatment compared with other plants. Shoot NO₃⁻ accumulation was associated with nitrate reductase activity (NRA). For instance, after 7 days of treatment, shoot NO₃⁻ concentration and NRA on a FW basis in 0 N plants were, respectively, 45 and 31% of full N plants. After transferring full N to 0 N for 7 days, all M. crystallinum had higher chlorophyll (Chl) content coupled with higher electron transport rate (ETR) and higher effective quantum yield of PSII, while full N plants had higher non-photochemical quenching (NPQ). The 0N plants had much higher concentrations of proline, total soluble sugar (TSS), and total ascorbic acid (ASC) than other plants. In conclusion, totally withdrawing NO₃⁻ from the growth media prior to harvest could be one of the strategies to reduce shoot NO₃⁻ concentration. Reduced NO₃⁻ supply further enhanced nutritional values as concentrations of proline, TSS, and ASC were enhanced markedly in M. crystallinum plants after transferring them from full N to 0 N.
    WOS© Citations 3Scopus© Citations 5  87  109
  • Publication
    Open Access
    LED quality impacts on plant growth and photosynthetic light use efficiency of halophyte vegetable Mesembryanthemum crystallinum grown under two saline conditions
    (2022) ;
    Qin, Lin
    There is very little study on the effects of LED quality on Mesembryanthemum crystallinum grown under different salinities. In this study, M. crystallinum was grown under red/blue (R/B) LED ratios of 0.9, 1.6. 2.0 and 2.8 with 100 and 500 mM NaCl and exposed to the same level of photosynthetic photon flux density, PPFD (290 µmol m‑2 s‑1, 12 h photoperiod). Fourteen days after transplanting, plants with 100 mM NaCl had significantly higher values of growth parameters including shoot and root fresh weight, total leaf area and specific leaf area than with 500 mM NaCl. Grown with 100 mM NaCl under R/B 0.9, M. crystallinum had significantly lower shoot FW and total leaf area than under other R/B ratios. However, LED quality did not seem to affect the growth parameters of M. crystallinum grown with 500 mM NaCl. All plants had similar higher leaf succulence and water content but lower leaf dry matter content with 100 mM NaCl than with 500 mM NaCl. Crassulacean acid metabolism (CAM) acidity of plants grown with 500 mM NaCl was about 4-fold higher than with 100 mM NaCl, indicating induction and stimulation of CAM photosynthesis. Chlorophyll fluorescence Fv/Fm ratios were greater than 0.8 for all plants, suggesting that maximum efficiency of PSII was unaffected by LED quality and salinity. M. crystallinum grown with 500 mM NaCl had lower electron transport rate, ETR but higher non-photochemical quenching, NPQ than with 100 mM NaCl, implying that photosynthetic light use efficiency was affected when switching C3 to CAM photosynthesis under high salt stress. M. crystallinum grown with100 mM NaCl had higher photochemical quenching, qP and ETR under R/B 0.9 than under R/B 2.8 and all plants with 500 mM NaCl. In conclusion, LED quality had different impacts on photosynthetic light-use efficiency of M. crystallinum grown under different salinities and thus resulting in different growth and productivity.
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  • Publication
    Open Access
    Integrated effects of root-zone temperatures and phosphorus levels on aeroponically-grown lettuce (Lactuca sativa L.) in the tropics
    (2009)
    Luo, Hong Yi
    ;
    Lee, Sing-Kong
    ;
    In this study, butterhead lettuce (Lactuca sativa L. cv. Baby Butter) plants were grown at three root-zone temperatures (RZTs): 25°C, 30°C and ambient-RZT (A-RZT) ranging from 26°C-42°C while their shoots were maintained at hot ambient temperature ranging from 26°C-42°C. Three phosphorus (P) concentrations: -25% P (minus P, 23.25ppm), control (31.00ppm) and +25% P (plus P, 38.75ppm) were supplied to the plants at each RZT using Netherlands Standard Nutrient Solution. Interactions between RZT and P concentrations on productivity, root morphology, maximum photosynthetic O2 evolution (Pmax), P uptake and its partitioning between shoot and root were studied. Lettuce plants grown with the plus P concentration at 25°C-RZT had the highest productivity, highest Pmax, highest shoot and root P concentrations. However, all the root morphological parameters studied were the greatest in plants grown with the minus P at 25°C-RZT. Higher P concentration in the solution and 25°C-RZT resulted in higher portion of the absorbed P partitioned to the shoots. Integrated effects of RZT and P concentration on the productivity, root morphology, photosynthesis and P uptake were discussed.
      428  217
  • Publication
    Open Access
    Productivity, photosynthetic light-use efficiency, nitrogen metabolism and nutritional quality of C4 halophyte Portulaca oleracea L. grown indoors under different light intensities and durations
    (2023) ;
    Gan, Shirin Jia Hui
    ;
    Qin, Lin
    Portulaca oleracea L. (known as purslane), is a nutritious facultative C4 halophyte. Recently, it has been successfully grown indoors under LED lightings by our team. However, basic understanding about the impacts of light on purslanes are lacking. This study aimed to investigate the effects of light intensity and duration on productivity, photosynthetic light use efficiency, nitrogen metabolism and nutritional quality of indoor grown purslanes. All plants were grown in 10% artificial seawater hydroponically under different photosynthetic photon flux densities (PPFDs) and durations and thus different daily light integrals (DLI). They are, L1 (240 µmol photon m-2 s-1, 12 h, DLI = 10.368 mol m-2 day-1); L2 (320 µmol photon m-2 s-1, 18 h, DLI = 20.736 mol m-2 day-1); L3 (240 µmol photon m-2 s-1, 24 h, DLI = 20.736 mol m-2 day-1); L4 (480 µmol photon m-2 s-1, 12 h, DLI = 20.736 mol m-2 day-1), respectively. Compared to L1, higher DLI promoted root and shoot growth and thus increased shoot productivity by 2.63-,1.96-, 3.83-folds, respectively for purslane grown under L2, L3, L4. However, under the same DLI, L3 plants (continuous light, CL) had significantly lower shoot and root productivities compared those with higher PPFDs but shorter durations (L2 and L4). While all plants had similar total chlorophyll and carotenoid concentrations, CL (L3) plants had significantly lower light use efficiency (Fv/Fm ratio), electron transport rate, effective quantum yield of PSII, photochemical- and non-photochemical quenching. Compared to L1, higher DLI with higher PPFDs (L2 and L4) increased leaf maximum nitrate reductase activity while longer durations increased leaf NO3 concentrations and total reduced nitrogen. There were no significant differences in leaf total soluble protein, total soluble sugar and total ascorbic acid concentrations in both leaf and stem regardless of light conditions. However, L2 plants had the highest leaf proline concentration but leaf total phenolic compounds concentration was higher in L3 plants instead. Generally, L2 plants had the highest dietary minerals such as K, Ca, Mg and Fe among the four different light conditions. Overall, L2 condition is the most suitable lighting strategy in enhancing productivity and nutritional quality of purslane.
    WOS© Citations 3Scopus© Citations 4  74  70