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  • Author or Editor: Margaret Mukami Gitau x
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Ao Liu, Jibiao Fan, Margaret Mukami Gitau, Liang Chen and Jinmin Fu

Bermudagrass [Cynodon dactylon (L.) Pers.] is a warm-season turfgrass that has the potential to improve saline and alkaline soils. However, its utilization is severely limited by high salinity. Therefore, it is urgent to enhance its tolerance to salt stress. Previous studies have proved that nitric oxide (NO) plays a vital role in various biological processes. However, the role of NO in bermudagrass response to salt is unknown. Our objective here was to investigate whether and how NO contributes to the protection of bermudagrass against salt stress in bermudagrass. In this study, sodium nitroprusside (SNP) served as the NO donor, while 2-phenyl-4,4,5,5-tetramentylimidazoline-l-oxyl-3-xide (PTIO) plus NG-nitro-L-arginine methyl ester (L-NAME) acted as the NO inhibitor. The treatment of bermudagrass with 400 mm salt solution occurred under different regimes: control, SNP, PTIO + L-NAME (PL). The results showed that 400 mm salinity caused significant toxicity to bermudagrass. However, SNP alleviated damage effect on plant growth and ionic balance as indicated by higher water content, chlorophyll content, higher chlorophyll a fluorescence (OJIP) curves and K+:Na+, Mg2+:Na+, and Ca2+:Na+ ratios. Also, lower levels of electrolyte leakage, malonaldehyde, H2O2, superoxide dismutase, peroxidase, and ascorbate peroxidase activities suggested that NO reduced the membrane injury and lipid peroxidation under salt treatment, while PL regime showed severe damage. In summary, our results suggest that NO has some beneficial effects on the maintenance of cell membrane stability, alleviation of oxidative damage and maintenance of ion homeostasis and plant photosythesis when bermudagrass is exposed to high salinity condition.

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Zhuangjun Zhao, Margaret Mukami Gitau, Tao Hu, Yan Xie, Longxing Hu and Jinmin Fu

Plants growing in salt-affected soils may have retarded growth and inhibited or altered metabolic processes. This study aims at investigating the impact of subsurface soil salinity on root growth and metabolic processes in perennial ryegrass (Lolium perenne). The seeds of perennial ryegrass (cv. Quick Start II) were planted in polyvinyl chloride (PVC) tubes (10 cm diameter × 42 cm long) for 2 months. The experiment consisted of three treatments: 1) control, 40 cm filled with sand–peat mixture (7 sand : 3 peat wt/wt); 2) T20, a 20-cm-deep layer of saline soil covered with a 20-cm-deep layer of sand–peat mixture; and 3) T30, a 30-cm-deep layer of saline soil covered with a 10-cm-deep layer of sand–peat mixture. Our study showed that soil salinity at the subsurface inhibited the growth of perennial ryegrass roots. Compared with the control, the root activity in saline soil layer decreased, whereas it remained high in the mixture-soil zone. The content of amino acids in the roots obtained from the surface soil (0–10 cm) in T30 was greater than that in both the T20 and the control regimes. The content of soluble sugars in the roots went up with the decrease of the depth of sand–peat mixture. The increased root activity and free amino acids content in the roots sampled from the upper soil layers coupled with the increased soluble sugars in the roots subjected to soil salinity stress in the bottom soil layer represents some adaptive responses and regulative mechanisms in perennial ryegrass.

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Zhengrong Hu, Erick Amombo, Margaret Mukami Gitau, Aoyue Bi, Huihui Zhu, Liang Zhang, Liang Chen and Jinmin Fu

Bermudagrass (Cynodon dactylon) is a typical and widely used warm-season turfgrass. Low temperature is one of the key environmental stress limiting its utility. However, little information is available about the differences of cold response between bermudagrass genotypes. Here, we analyzed antioxidant defense system and fatty acid composition in cold-resistant genotype WBD128 and cold-sensitive genotype WBDg17 exposed to chilling stress. Low temperature (4 °C) significantly decreased the relative water content, whereas increased the H2O2 and O2 contents, more profoundly for WBDg17. Under chilling condition, WBD128 had higher anti O2 activity than WBDg17. Besides, the contents of total glutathione, reduced glutathione (GSH) and its oxidized form (GSSG) were markedly increased by low temperature in both genotypes, whereas WBD128 had significantly higher values of GSH, total glutathione, and GSH/GSSG ratio than WBDg17. Moreover, chilling stress increased saturated fatty acids (SFAs) percentage (palmitic acid and stearic acid) in WBDg17. After chilling treatment, the proportion of linoleic acid decreased in both genotypes, particularly in WBDg17. As for unsaturated fatty acids (UFAs), the percentage of linolenic acid was increased in WBD128. In addition, chilling treatment decreased the values of double bond index (DBI), UFA/SFA ratio as well as degree of unsaturation in WBDg17. Finally, chilling stress altered the expression patterns of the genes, which encode one kind of late embryogenesis abundant proteins (LEA), superoxide dismutase (Cu/Zn SOD) C-repeat-binding factor/DRE-binding factor (CBF1), and peroxidase (POD-2). Collectively, our results revealed that natural variation of chilling tolerance in bermudagrass genotypes may be largely associated with the alterations of antioxidant defense system and fatty acid composition.