Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: Hongmei Wang x
Clear All Modify Search

Heat stress may limit the growth of turfgrasses through the induction of oxidative stress, causing cellular and physiological damage. The objective of the study was to examine the association of heat and oxidative stresses between warm-season (C4) and cool-season (C3) turfgrasses. Plants of zoysiagrass (Zoysia matrella L. Merr. cv. Manila) (C4) and tall fescue (Festuca arundinacea Shreber cv. Barlexus) (C3) were exposed to optimal temperature conditions (24 °C for tall fescue and 34 °C for zoysiagrass) or heat stress (10 °C above the respective optimal temperature for each species) in growth chambers. Zoysiagrass exhibited less severe decline in turf quality and photochemical efficiency and less severe oxidative damage in cellular membranes as demonstrated by lower membrane electrolyte leakage and lipid peroxidation compared with tall fescue when both were exposed to heat stress. The activities of superoxide dismutase (SOD) and peroxidase (POD) declined with heat stress for both species, but to a lesser extent in zoysiagrass than in tall fescue, whereas catalase activity did not change significantly under heat stress and did not exhibit species variation. Our results demonstrate that the superior heat tolerance in zoysiagrass in comparison with tall fescue was associated with greater oxidative scavenging capacity as a result of the maintenance of higher SOD and POD activities.

Free access

The objective of this study was to compare differential nutrient responses to heat stress in relation to heat tolerance for warm-season (C4) common bermudagrass [Cynodon dactylon (L.) Pers.] and cool-season (C3) kentucky bluegrass (Poa pratensis L.). Both species were exposed to two temperature regimes in growth chambers: optimal day/night temperature conditions (24/20 °C for kentucky bluegrass and 34/30 °C for bermudagrass) or heat stress (10 °C above the respective optimal temperature for each species). Heat injury in leaves was evaluated and the concentrations of several major macronutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] in both grass species were measured at 0, 7, 14, 21, and 28 days of treatment. Heat stress reduced leaf photochemical efficiency and cellular membrane stability in both species, but bermudagrass leaves exhibited less damage in these parameters than kentucky bluegrass. Heat stress caused a significant decline in N, P, and K concentration, beginning at 7 days in kentucky bluegrass, but had no significant effects on N, P, and K concentration in bermudagrass during the 28-day treatment period. The concentration of Ca and Mg increased under heat stress in both kentucky bluegrass and bermudagrass, but there were no significant differences between the species under optimal or high-temperature conditions, suggesting they were not involved in heat responses in either species. The differential responses of N, P, and K to heat stress could at least partially account for the differences in heat tolerance between the two species and demonstrate the importance of sufficient N, P, and K in turfgrass adaptation to heat stress.

Free access

The accumulation of different types of metabolites may reflect variations in plant adaptation to different severities or durations of drought stress. The objectives of this project are to examine changes in metabolomic profiles and determine predominant metabolites in response to short-term (6 days) and long-term (18 days) drought stress with gas chromatography–mass spectrometry analysis in a C4 perennial grass species. Plants of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis cv. Tifdwarf) were unirrigated for 18 days to induce drought stress in growth chambers. Physiological responses to drought stress were evaluated by visual rating of grass quality, relative water content, photochemical efficiency, and electrolyte leakage (EL). All parameters decreased significantly at 6 and 18 days of drought stress, except EL, which increased with the duration of drought stress. Under short-term drought stress (6 days), the content did not change significantly for most metabolites, except methionine, serine, γ-aminobutyric acid (GABA), isoleucine, and mannose. Most metabolites showed higher accumulation under long-term drought stress compared with that under the well-watered conditions, including three organic acids (malic acid, galacturonic acid, and succinic acid), 10 amino acids (proline, asparagine, phenylalanine, methionine, serine, 5-hydroxynorvaline, GABA, glycine, theorine, valine), seven sugars (sucrose, glucose, galactose, fructose, mannose, maltose, xylose), one nitrogen compound (ethanolamine), and two-sugar alcohol (myo-inositol). The accumulation of those metabolites, especially malic acid, proline, and sucrose, could be associated with drought adaptation of C4 hybrid bermudagrass to long-term or severe drought stress.

Free access

Fritillaria crassicaulis S. C. Chen is a precious traditional Chinese medicine, but the number of populations has declined rapidly due to overexploitation. An artificial rapid propagation system was established to screen the suitable plant regeneration method and to explore the efficient propagation method, useful for propagation technology or for further research and development of F. crassicaulis. This study selected scale as the experimental material, set Murashige and Skoog (MS) medium as the basic medium, and optimized the types and proportions of plant growth regulator (PGR) suitable for callus induction, bulblet differentiation and proliferation, and plant regeneration by means of single-factor, full-factorial, and L9 (3)4 orthogonal experiments. Results demonstrate that in the experiment with single exogenous PGR, the high concentration of 6-benzylaminopurine (6-BA) was significantly better than kinetin (KT) to induce bulblets, 2, 4-dichloroacetic acid (2, 4-D) had a significant effect on callus induction, and a higher concentration of naphthaleneacetic acid (NAA) was beneficial to the occurrence and growth of bulbs, but the rooting effect promoted by indole butyric acid (IBA) was preferable to that by NAA. In MS medium with 0.5 mg/L 2, 4-D and 1.5 mg/L 6-BA, a large number of yellowish-green compact calli could be induced from the scales with the calli induction frequency at 93.3%, and about 11.4% materials directly differentiated bulblets. In the subsequent orthogonal experiment, after the scales were cultured in MS medium with 2.0 mg/L 6-BA, 0.5 mg/L 2, 4-D, and 0.1 mg/L NAA for 20 days, the small yellow and white globular protuberances formed near the incision, but no callus appeared, and many protuberances appeared on the surface of the scales. After 60 days, the protuberances at the incision developed into bulblets directly, while protuberances on the surface of the scales developed into few bulblets but crowded “leaf spines,” which gradually died and disappeared in the later culture; the proliferation coefficient was ∼6.30 then. Experimental results indicate that the optimal rooting medium for bulblets was 1/2MS medium with 2.0 mg/L IBA and 1.0 mg/L activated carbon (AC), with the rooting rate at 95.6%. This study identifies bulblet regeneration of F. crassicaulis, and an efficient direct organogenesis method was established: regenerated bulblets could be induced from scales in one step, so a large number of regenerated plants with the same genotype could be obtained in a short time.

Open Access

Fatty acid metabolism may be involved in plant adaptation to drought stress. The objective of this study was to identify saturated and unsaturated fatty acids associated with leaf dehydration tolerance by comparing fatty acid composition and unsaturation levels at equivalent leaf water status of two bermudagrass genotypes contrasting in drought resistance. A drought-resistant hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) genotype (‘Tifway’) and a drought-sensitive bermudagrass (C. dactylon) genotype (‘C299’) were maintained under well-watered (control) or water-withheld (drought) conditions. Drought treatment was imposed until soil water content decreased to 5% or leaf relative water content (RWC) dropped to 28% to 29%. ‘Tifway’ maintained higher RWC and lower electrolyte leakage (EL) at 5 and 10 days of drought stress. Leaves of ‘Tifway’ maintained lower EL when RWC of both genotypes declined to the same level of water deficit (28% to 29%) by the end of drought periods. The degree of fatty acid unsaturation, expressed as the double bond index, decreased in both genotypes during drought stress, which was mainly associated with the decline in linoleic (C18:2) and linolenic acids (C18:3) and an increase in palmitic (C16:0) and stearic acids (C18:0). A lipid composition characterized by a greater amount of unsaturated fatty acids was detected in ‘Tifway’ relative to ‘C299’ exposed to the same level of water deficit, mainly as a result of a greater content of C18:2 and a lower content of C16:0 and C18:0. Our results suggest that the ability to maintain a greater composition of unsaturated fatty acids in membrane lipids may contribute to superior leaf dehydration tolerance in bermudagrass.

Free access

Salinity is a detrimental abiotic stress for plant growth in salt-affected soils. The objective of this study was to examine photosynthetic responses to salinity stress in two warm-season turfgrasses differing in salinity tolerance. Salt-tolerant species seashore paspalum (Paspalum vaginatum) and salt-sensitive species centipedegrass (Eremochloa ophiuroides) were exposed to salinity at three NaCl concentrations (0, 300, and 500 mm) in a growth chamber. Turf quality, relative water content (RWC), and leaf photochemical efficiency (Fv/Fm) declined, whereas electrolyte leakage (EL) increased under the two NaCl regimes for both grass species, and the changes were more dramatic in centipedegrass than that in seashore paspalum as well as in the higher salinity concentration. Two grass species showed different phytosynthetic responses to salinity stress. The earlier inhibition of photosynthesis in seashore paspalum was mainly associated with stomatal closure. As salinity increased and salinity stress prolonged, the inhibition of photosynthesis in seashore paspalum was mainly associated with non-stomatal factors. The inhibition of photosynthesis in centipedegrass was associated with both stomatal closure and non-stomatal factors at both salinity levels. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated the Rubisco large subunit had no obvious decrease during the whole stress period under the 300-mm and 500-mm treatments in seashore paspalum, whereas it significantly decreased in centipedegrass under both the 300-mm and 500-mm treatments. The results indicated that the superior salinity tolerance in seashore paspalum, compared with centipedegrass, could be attributed to its maintenance of Rubisco stability, chlorophyll content, photochemical efficiency as well as photosynthetic rate (Pn) capacity under salinity stress.

Free access

Sucrose phosphate synthase [SPS (EC 2.4.1.14)] is thought to play a critical role in sucrose accumulation in muskmelon (Cucumis melo L.) fruit. A full-length cDNA clone encoding sucrose phosphate synthase was isolated from muskmelon by reverse transcriptase–polymerase chain reaction and rapid amplification of cDNA ends. The clone, designated CmSPS1, contains 3377 nucleotides with an open reading frame of 3162 nucleotides. The deduced 1054 amino acids sequence showed high identities with other plant sucrose phosphate synthases. Northern blot analysis indicated that CmSPS1 was expressed in leaves, stems, and mature fruit, but was not detected in roots or flowers. Moreover, the mRNA accumulation of CmSPS1 started at 25 days after pollination (DAP) and reached highest level in mature fruit. Interestingly, both sucrose content and SPS activity increased dramatically between 20 and 30 DAP during fruit development, suggesting that sucrose accumulation may be linked to the CmSPS1 transcript level in muskmelon fruit.

Free access

Stony hard (SH) peach (Prunus persica) fruits produce no ethylene and clingstone-type SH peaches have a crispy flesh texture; however, freestone-type SH peach fruits ripen to a soft, mealy state. During this study, we compared and analyzed changes in the microstructure, cell wall polysaccharides, and candidate cell wall-related genes of freestone-type SH ‘Zhongtao 14’ (‘CP14’), ‘Zhongtao White Jade 2’ (‘CPWJ2’), clingstone-type SH ‘Zhongtao 13’ (‘CP13’), and ‘Zhongtao 9’ (‘CP9’) during fruit ripening. The parenchyma cells of mealy freestone-type SH peaches became detached, were single, dried, and irregularly arranged, and remained intact in comparison with the nonmealy clingstone-type SH peaches. Methyl-esterified homogalacturonan was strongly immunolabeled in the cell wall of clingstone SH peaches; however, nonmethylated homogalacturonan was weakly immunolabeled in freestone SH peaches. A transcriptome analysis was performed to investigate the molecular mechanism of the mealiness process. A principal component analysis indicated that ‘CP14’ S4 III (mealy) could be distinguished from the samples of ‘CP13’ (S4 I, S4 II, S4 III) and ‘CP14’ (S4 I, S4 II). The highly coexpressed gene modules linked with firmness were found using a weighted gene coexpression network analysis; 189 upregulated genes and 817 downregulated genes were identified. Six upregulated cell wall-related genes (PpPG1, PpPG2, PpAGP1, PpAGP2, PpEXT1, and PpEXP1) and one downregulated cell wall-related gene (PpXET2) were involved in the mealiness process during freestone-type SH fruit ripening. These findings will improve our understanding of the relationship between clingstone, freestone, and stony hard fruits and lay the foundation for further exploration of the mechanisms underlying the softening of peach fruits.

Open Access