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Turfgrass performance under drought stress is impeded by plant water deficit and oxidative damage, which might be improved by the external application of osmoprotectants. Creeping bentgrass (Agrostis stolonifera L.) is a valuable species for low-cut golf surfaces as a result of its high density and fine texture. However, weak tolerance to drought stress is a primary shortcoming. In this study, the effect of exogenous glycinebetaine (GB) pretreatment on mitigating the damage from drought stress in creeping bentgrass cultivar ‘T-1’ was evaluated. Pieces of creeping bentgrass sod were subjected to four treatments: 1) well-watered control, 2) well watered and sprayed with 100 mm GB, 3) drought stress, and 4) drought stress and sprayed with 100 mm GB. Drought stress resulted in a remarkable decrease in turf quality (TQ), relative water content (RWC), and chlorophyll content, with significant increases in superoxide anion content (O2 –), malondialdehyde (MDA) content, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activity. In contrast, pretreatment with 100 mm GB decreased the O2 – and MDA content in water-stressed plants, and increased turf quality, chlorophyll content, SOD, CAT, and POD activity. Meanwhile, the expression level of the psbA, SAMS4, CMO, and ACS1 genes in leaf samples collected during the drought-stress stage was elevated in GB pretreatment. Notably, SAMS4 gene expression in GB pretreatment was significantly greater than in the untreated GB groups subjected to water stress. These results suggested that GB could mitigate the adverse effect of water stress on creeping bentgrass. The amelioration related strongly to the maintenance of the antioxidant enzyme system, accumulated endogenous compatible metabolites, and the elevation of gene expression levels. These findings lead us to conclude that GB pretreatment could be used as an ameliorative agent for creeping bentgrass against the deleterious effects of water stress.
Off-season flowering in red pitaya (Hylocereus sp.), a long-day plant, can be achieved using night-breaking (NB) treatment. Among the stages of bud development, stage 0 referred to induced but not yet differentiate any bracteole and stage 3 was the stage right before emerging floral buds and the bracteole differentiation was completed. Unlike floral bud emergence, bracteole differentiation was independent of the daylength and strongly influenced by the environmental temperature. The buds of higher stages were more effective in response to NB treatment and more sensitive to chilling injury (CI). Consequently, off-season flowers in autumn and winter trials were derived mainly from stage 2 and 3 buds and from stage 0 and 1 buds, respectively. In southern Taiwan, low night temperature between 10 Jan. and 7 Feb. 2011 may be the major factor, which delay bud development in off-season production. Therefore, we conducted a heating experiment in winter off-season production to proof our hypothesis and concluded that NB treatment should be applied along with night temperature elevation or after mid-February when the minimum night temperature is increasing.
The uptake of water and nutrient in potted plants is greatly affected by irrigation conditions, and it influences the plant growth. This study aimed to examine the correlations between basic environmental parameters and plant growth in potted plants (kalanchoe) and to develop the models for adequate irrigation control. Growth chambers were developed for the experiments, and four levels of photosynthetic photon flux (PPF) were treated by using different numbers of shading films and lamps. Kalanchoe blossfeldiana cv. New Alter, grown in the nutrient-flow wick culture (NFW) system, was used. The 7-cm pots were filled with a 7:3 mixture of peat moss and perlite medium (v/v). The initial water content was set at about 26%. A total of 150 pots and plants with different growth stage were prepared for 4 weeks. A wick [12 × 1 cm (L × W)] was used in each pot. Leaf areas of plants and surface areas of the medium were analyzed by a plant image analysis system. For measuring the water losses of plants and pots during the growth stage, the initial water content of the substrates was maintained at about 55%. Water losses were measured at 9, 11, 13, 15, and 17 hours for all experiment periods by using an electron balance. Two models were developed for estimating water losses by evapotranspiration and water intake by water absorption. Finally, a model for estimating water content in the medium was tried. Growth and environment parameters showed high correlations with transpiration and evaporation, respectively. There was an interactive effect of VPD and PPF on the change of evapotranspiration. The amount of absorption was increased by time and decreased with increase of initial water content.
Leaf color mutants play an important role in our understanding of chlorophyll biosynthesis and catabolism. In this study, we obtained a yellow-green leaf mutant hy in an ethyl methanesulfonate mutagenized population of chinese cabbage (Brassica rapa ssp. pekinensis). The hy phenotype was controlled by a recessive allele at a single locus. The intrinsic photochemical activity of photosystem II (PSII) is impaired in hy, suggesting that absorbed light energy is not efficiently transferred from the light-harvesting complexes antenna to the PSII reaction centers and dissipated as heat or fluorescence. We measured chlorophyll content and chlorophyll precursors and analyzed the expression of key genes in the chlorophyll synthetic pathway in hy and wild type. The mutation phenotype was consistent with inhibited expression of chlorophyll a oxygenase (CAO) gene in the chlorophyll synthetic pathway. In mutant hy, CAO cDNA was cloned so that a C to T mutation at 1099 bp caused a conserved proline (Pro) to serine (Ser) mutation at the 367th amino acid in C-domain, which changed the secondary structure of CAO protein. We speculate that the mutation amino acid changed in the C-domain may affect the catalytic function in mutant CAO.
Denphal-type Dendrobium is the most popular orchid for cut flower and potted plant trade. To improve commercial traits, many novel cultivars have been produced through hybridization by commercial breeders. However, the genetic relationship of most cultivars is unclear, thus hindering the progress of Denphal-type Dendrobium breeding programs. Therefore, the development of molecular markers is encouraged to identify different cultivars. In this study, based on the transcriptome database of the Denphal-type Dendrobium ‘Red Bull’, the polymorphisms expressed sequence tag-derived simple sequence repeat (EST-SSR) were developed from 100 pairs EST-SSRs that were randomly selected from the EST-SSR database. The genetic relationship of 42 Denphal-type Dendrobium cultivars was analyzed according to the developed EST-SSRs. Then, the transferability of EST-SSRs was analyzed by performing a relationship analysis of 40 Dendrobium species. The results showed that a total of 5174 potential EST-SSR markers were identified with 4486 unigene sequences, and 5289 primer pairs were successfully designed. Of the selected 100 pairs of EST-SSRs, a total of 86 pairs produced the expected polymerase chain reaction products of the primary screening, 58 pairs produced the expected fragment size, and 20 pairs showed polymorphisms. Furthermore, the dendrogram of 42 cultivars showed that at a genetic distance of 0.15, the cultivars collected were grouped into five clusters of three major clusters and two minor clusters; all these clusters had the same characters of each cluster. The transferability analysis showed that 18 of the 20 EST-SSR markers among the 40 Dendrobium species were polymorphic. Overall, this study developed EST-SSR markers and will be valuable to facilitating genetic diversity in Denphal-type Dendrobium cultivars and Dendrobium species.
Denphal-type Dendrobium is the famous cut and potted flower in the world, and most cultivated in tropical and subtropical regions. However, it often suffers from cold in winter in subtropical regions. To verify the physiological response of Denphal-type Dendrobium under low temperature in this study, the mature and young plantlets of Dendrobium Udomsri Beauty were treated under 15, 10, and 5 °C, respectively. And then the electrical conductivity (EC), soluble protein, soluble sugar, free proline, malondialdehyde (MDA), chlorophyll content, and the rate of defoliation after regrowth were measured. The results showed that both mature plant and young seedlings of Dendrobium Udomsri Beauty, the EC, soluble protein, soluble sugar, free proline, MDA content, and defoliation rate were increased with the decrease of treatment temperature and the extension of treatment times. The content of chlorophyll decreased gradually with the decrease of treatment temperature and the extension of treatment times. The correlation analysis showed that soluble sugar, free proline, MDA, chlorophyll content, and defoliation rate were significantly correlated with the semi-lethal temperature. It is indicated that the content of free proline, MDA, chlorophyll, and defoliation rate could be used as the effective indexes for the comprehensive assessment of cold tolerance of Dendrobium Udomsri Beauty.
Red pitaya (Hylocereus sp.), which flowers between May and October and sprouts between November and May in Taiwan, has been confirmed to be a long-day plant. The areoles on the old shoots may be induced to flower after the March equinox naturally, and the floral bud formation occurs in two to three waves from May to October. We conducted experiments on photoperiodic regulation of floral bud formation from June to Dec. 2009 and tested the feasibility of off-season production in 2011. Shortening summer daylength to 8 h inhibited the areoles at the distal end of the shoots to develop into floral buds and promoted sprouting at the proximal ends of the shoots. Night-breaking treatment between the September equinox and the winter solstice led to floral bud formation. The critical daylength seemed to be ≈12 h, and night-breaking treatment would be applicable between the September and the next March equinoxes to produce off-season crops. The duration of night-breaking required for flower differentiation was longer in the cooler than in the warmer season. Four weeks of night-breaking treatment was sufficient to promote flowering in late fall (mid-October to mid-November), but 3 months were required to generate similar result in the winter and early spring (January to March) in southern Taiwan.
Soil polarization for 98 days in 1985 resulted in a 91% reduction of weeds present in collard greens (Brassica oleracea acephafa L.) plots during 1986. Soil solarization was more effective in controlling weeds in collard green plots when compared to an application of Dacthal-75W herbicide in nonsolarized plots. Collard green plants grown in solarized soil showed an increase in yield and other growth responses. Soil samples from the rhizosphere of plants grown in solarized soil showed higher population levels of bacteria and thermotolerant fungi than from nonsolarized soil. There were significant negative responses in marketable yield and root growth of collard greens and in soil microflora in solarized soil in response to Dacthal-75W herbicide application. Chemical name used: dimethyltetrachloroterephthalate (Dacthal-75W).