The effects of light quality emitted by light-emitting diodes (LEDs) on the growth and morphogenesis, and concentrations of endogenous phenolic compounds of Protea cynaroides L. plantlets in vitro, were investigated. Plantlets were cultured under four light treatments: conventional fluorescent lamps (control), red LEDs (630 nm), blue LEDs (460 nm), and red + blue LEDs (1:1 photosynthetic photon flux). Four phenolic compounds extracted from the plantlets were analyzed: 3,4-dihydroxybenzoic acid, gallic acid, caffeic acid, and ferulic acid. The highest rooting percentage was observed in plantlets cultured under red LEDs (67%) compared with 7% under conventional white fluorescent light, 13% under blue LEDs, and 13% under red + blue LEDs. The highest number of roots per plantlet was also found under red LEDs, whereas a significantly lower number of roots per plantlet was obtained under the other light treatments. Furthermore, red light promoted the formation of new leaves in P. cynaroides plantlets. However, the highest leaf dry weight (53.8 mg per plantlet) was found in plantlets irradiated by the combination of red and blue LEDs. Phenolic analyses showed that the lowest concentrations of 3,4-dihydroxybenzoic acid (4.3 mg·g−1), gallic acid (7.0 mg·g−1), and ferulic acid (7.4 mg·g−1) were detected in plantlets exposed to red light, whereas those irradiated by white fluorescent light contained the highest concentration. A significant inverse correlation (r = –0.419) was established between 3,4-dihydroxybenzoic acid and rooting percentage. Strong inverse correlations were also established between 3,4-dihydroxybenzoic acid and number of roots per plantlet (r = –0.768) as well as between ferulic acid and number of roots per plantlet (r = –0.732). These results indicate that the stimulation of root formation in P. cynaroides plantlets under red LEDs is the result of the low endogenous concentrations of 3,4-dihydroxybenzoic acid and ferulic acid.
How-Chiun Wu and Chun-Chih Lin
The effects of CO2 enrichment on the in vitro growth and acclimatization of Protea cynaroides L. plantlets were investigated. Three CO2 enrichment concentrations were used: 0 (control), 1000, 5000, and 10000 μmol·mol−1. Plantlets in the control treatment were cultured on half-strength Murashige and Skoog (MS) medium supplemented with sucrose, whereas those enriched with different CO2 concentrations were grown on sucrose-free MS medium. Compared with the control, significant improvements were observed in the growth of plantlets enriched with CO2 irrespective of the concentration. Plantlets enriched with 5000 μmol·mol−1 CO2 produced the highest number of leaves and the largest leaf area. In addition, the photosynthetic ability of plantlets enriched with CO2 was enhanced, which resulted in significant increases in shoot growth and dry matter accumulation. In particular, the shoot dry weight of plantlets cultured in 5000 μmol·mol−1 CO2 and 10000 μmol·mol−1 CO2 were, respectively, 2.1 and 4.2 times higher than those without CO2 enrichment. During acclimatization, the survival percentage, rooting percentage, and leaf number of plantlets grown in elevated CO2 were, respectively, up to 4.5, 1.8, and 2.7 times higher than plantlets without CO2 enrichment. The improvements in survival percentage and ex vitro growth of these plantlets were the result of their enhanced photosynthetic ability in vitro, which resulted in the production of high-quality plantlets. Significant improvements in the overall growth of P. cynaroides plantlets were achieved through the use of photoautotrophic micropropagation with CO2 enrichment.
Furn-Wei Lin, Kuan-Hung Lin, Chun-Wei Wu, Yu-Sen Chang, Kuan-Hung Lin, and Chun-Wei Wu
Plant biostimulants have received increasing attention in recent years because of their positive effects on crop performance and contribution to agro-ecological sustainability. The aim of this study was to determine the influence of betaine and chitin treatments, alone and in combination, on lettuce plants by changes in the morphology and physiology of plants exposed to regulated deficit irrigation (RDI). Plants were subjected to full irrigation (FI; no water deficiency treatment, field capacity >70%) and RDI (field capacity <50%) conditions until the end of each experiment. We recorded plant yield–related traits, net photosynthesis, and water use efficiency (WUE) values weekly for 4 weeks and carried out three individual experiments to assess the efficacy of biostimulant and irrigation treatments. Betaine (0, 50, and 100 mm/plant) was foliar-treated every 2 weeks during Expt. 1, whereas chitin (0, 2, and 4 g/kg) was applied to the soil at the beginning of Expt. 2. We then applied the optimal concentration of each chemical alone or in combination to the plants as Expt. 3. Compared with negative control, the application of 50 mm betaine and 2 g/kg chitin significantly increased leaf area (LA) per plant by 48.5% and 25.6%, respectively. Furthermore, 50 mm betaine and 2 g/kg chitin treatment showed a clearly protective effect in RDI plants, enhancing their total fresh weights by 26.10% and 75.0%, respectively, in comparison with control. Comparing WUEyield and WUEbiomass, chemical-treated plants had higher values than control. Betaine (50 mm) or chitin (2 g/kg) treatments alone significantly elevated LA, fresh shoot weight, total fresh and dry weights, net photosynthesis, and WUE values, and boosted the water stress tolerance of lettuce under RDI compared with controls. However, a combined treatment of 50 mm betaine and 2 g/kg chitin did not increase the levels of all yield traits under RDI compared with individual chemical treatment. Most leaves appeared healthy, green, and had visually less leaf chlorosis when treated with chitin or betaine under RDI compared with untreated plants subjected to RDI. Our study indicates that applying betaine and chitin improves plant performance against water supply limitations and highlights their potential for the sustainable production of lettuce.
Fure-Chyi Chen, Wan-Ling Wu, Chun-Hua Pan, Irwin Yau-Yuan Chu, and Yau-Wen Yang
Molecular markers by random amplified polymorphic DNAs were used to evaluate the genetic variation among different Oncidium accessions. It is possible to distinguish different registered Oncidium hybrids, including Gower Ramsey, Sweet Sugar, and Taka using nine random primers. Furthermore, variation was also detected within different cultivars derived from same hybrids. For example, several cultivars of Gower Ramsey could be distinguished based on molecular markers. Based on dendrogram, the investigated cultivars were clustered into several groups. Onc. Gower Ramsey and its selected cultivars were in one group. Onc. Sweet Sugar, Onc. Taka and Onc. Sharry Baby `Sweet Fragrance' were clustered in separate groups.
Wenlei Guo, Li Feng, Dandan Wu, Chun Zhang, and Xingshan Tian
Widespread herbicide-resistant weeds and severe insect pest infestations pose a challenge to the preplant pest management (PPPM) strategy currently in use in leaf vegetable fields in southern China. The aim of this study was to develop a new weed and insect control method for use before planting leaf vegetables in southern China. Two flaming machines (a tractor mounted and a trolley flaming machine) were designed, and their efficacies for the control of insect and weed pests were evaluated and compared in two field trials. With liquefied petroleum gas (LPG) at 101 kg·ha−1, flaming machines reduced plant numbers by 86.7% to 98.8% 2 days after treatment (DAT), which was equal to or higher than the reduction after application of paraquat at 900 g·ha−1. Some weed species, especially awnless barnyard grass (Echinochloa colona) and goosegrass (Eleusine indica), regrew at 7 DAT, resulting in a decrease in control efficacy. Flaming machines also reduced the number of diamondback moth (Plutella xylostella) larvae by 83.0% to 88.2% and the number of adult striped flea beetles (Phyllotreta striolata) by 64.9% to 80.9%. This is the first report on flaming treatment in China to show that this method is a promising alternative to chemical pesticides for PPPM in leaf vegetable fields.
Kuan-Hung Lin, Shao-Bo Huang, Chun-Wei Wu, and Yu-Sen Chang
Exogenous application of either salicylic acid (SA) or calcium chloride (CaCl2) to alleviate heat stress has been extensively studied. However, the effects of combined SA and CaCl2 treatment on the heat tolerance of poinsettia have been poorly studied. This study investigated the role of a foliar spray comprising SA and CaCl2 in managing heat tolerance of three poinsettia (Euphorbia pulcherrima Willd.) cultivars, Noel, Winter Rose (WR), and Ice Punch’ (IP). Plants were pretreated with SA, CaCl2, or combined SA and CaCl2 and then exposed to a temperature of 42 °C for 1 hour. Changes in the relative injury (RI) percentage, malondialdehyde (MDA) content, and antioxidant enzyme activities were determined. All plants were then placed in an environment-controlled greenhouse for 14 days and evaluated. Lateral bud sprouting (%), new leaf numbers, and phenotypic appearance were recorded. Results revealed that the three poinsettia cultivars varied in their appearance, morphological growth patterns, and ability to tolerate high-temperature stress. Plant growth of ‘Noel’ was more robust than that of ‘WR’ and ‘IP’, which were considerably affected by heat stress, resulting in brown, withered leaves and defoliation. In general, the effects of the combined application of SA and CaCl2 on heat-tolerant ‘Noel’ were superior to those of individual applications and no treatment (for control groups) in terms of the RI percentage, lateral bud sprouting (%), and appearance under heat stress. Application of combined SA and CaCl2 for ‘Noel’ plants was more beneficial for enhancing catalase activity and resulted in the effective alleviation of decreased malondialdehyde content under heat stress. Treatment including 200 μΜ SA and 10 mm CaCl2 may alleviate heat stress and may prove useful in breeding programs focused on improving poinsettia cultivars.
Yingchao Lin, Dejun Kong, Zhihong Wang, Yi Chen, Zhixiao Yang, Chun Wu, Hui Yang, and Lili Chen
Tobacco is traditionally an industrial crop that is used for manufacturing cigarettes. However, due to health concerns and global tobacco control movements, alternative uses of tobacco are urgently needed to support tobacco farmers and vendors. Tobacco is also an oilseed crop with an oil yield ranging from 30% to 40 of its dry weight. However, there is still no information on the effects of nitrogen application on tobacco seed yield and seed oil production. The objective of this study was to evaluate the effects of N fertilization (90, 120, 150, and 180 kg·ha−1 N) on the seed yield, oil content, fatty acid composition, and seed germination characteristics of tobacco plants at two locations. The results showed that applying increasing amounts of N to tobacco plants significantly increased their total seed yields and oil content. Nitrogen application also modified the fatty acid composition of the seed oil, as more unsaturated fatty acids were produced under the increasing N application rate treatments than under the control. Moreover, increasing the N application rate generally significantly increased the yields of individual fatty acids as well. Nevertheless, the increased seed oil content and altered fatty acid composition did not affect seed germination traits, as the seed germination potential and rate showed no obvious change among treatments or the control. The height and size of the tobacco plants also increased with the increasing N application rate, which would be beneficial for increasing biomass production for bioenergy. This study shows for the first time the feasibility of increasing the seed and oil yields and modifying the fatty acid composition of tobacco plants by increasing N addition.