Physiological responses of C4 grasses to prolonged heat stress

C4 grasses are best adapted to the transition, warm-arid, and warm-humid climatic zones and have the ability to acquire thermotolerance by exposure to acute heat stress. Exposure to sub-lethal temperatures results in changes in physiological, biochemical, metabolic, and molecular processes. The response of two warm-season grasses to prolonged heat stress was investigated. Plants of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis ‘Tifway’) and Japanese lawn grass (Zoysia japonica Steud. ‘Meyer’) were exposed for 168 h to supraoptimal temperature conditions (47°C) in controlled-environment chamber. Compared with zoysiagrass, bermudagrass showed greater damage. Metabolite profi les were affected by prolonged heat exposure, with signifi cant differences between these species. Consistent differences were found in total soluble sugars accumulation over the study period and severity of plant organ senescence. Bermudagrass roots were more affected, as compared to leaves. Leaf proteins expression determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed an early degradation in zoysiagrass, as thermal exposure proceeded. A signifi - cant net decline in protein content was observed after 48 h of exposure, while in bermudagrass an analogous decline was not detected until 96 h of treatment. Although heat stress is not considered a detrimental factor to C4 grass species, the two species showed signifi cant differences in their physiological response to continuous high temperatures

Fructan metabolism in tall fescue calli under different environmental condition

Several grasses usually accumulate high levels of fructans at low temperature or in the presence of high sugar supply. Fructans enhance plant resistance in adverse environmental conditions thanks to their vacuolar  localization which allow osmotic adjustments. Tall fescue calli do not show mature vacuoles due to its  anatomic characteristics, and these in vitro cultures can provide more knowledge about the fructan rule in  unspecialized tissues especially during stress conditions. The aim of this study was to evaluate the sugar  metabolism in embryogenic calli of tall fescue fed with different sucrose concentrations (0, 50 or 100 mM)  during growth culture, kept at “control” or “cold” temperatures (23 or 4°C, respectively). In the presence of  sucrose (50 or 100 mM), embryogenic calli accumulated fructans under control conditions. On the other hand,  the accumulation is inhibited by the simultaneously sugar supply and cold treatment while invertase activity  increased. From our data, cold temperature and high sucrose concentration seemed to be negatively  correlated in the fructans biosynthetic pathway in tall fescue in vitro cultures.Key words: Cold, Festuca arundinacea, invertase, sucrose:sucrose fructosyltransferase (SST), sugars

Carbohydrate content, characterization and localization in bermudagrass stolons during establishment

Abstract Turfgrasses are continuously exposed to a wide range of detrimental stresses, such as mowing, traffic, low or high temperatures, salinity, drought, UV, hypoxia etc. Plant responses to stimuli involve nearly every aspect of plant physiology and metabolism. Carbohydrates, primary sucrose and starch, as principal metabolic products of photosynthesis, are stored in bermudagrass (Cynodon spp.) in stolons and rhizomes. Total nonstructural carbohydrates (TNC) levels have been used as indicators of health and physiological status in bermudagrass. TNC levels vary during the year and are weakly affected by N source. Establishment is a critical phase of bermudagrass management. The objectives of this research were to assess and characterize stolon carbohydrate content in nine bermudagrass cultivars during the full establishment phase in relation to establishment rates. Morphological and growth analyses showed distinct properties among the cultivars selected for this study. Significant differences in turf co..

Winter Colour Retention and Spring Green-Up of Zoysiagrass Genotypes in Southern Europe

Zoysiagrass (Zoysia spp. Wild.) is a sustainable choice for the Mediterranean area, being identified as grass species adapted to low-input environments (limited water requirements, no fertilizer or pesticides after establishment). A distinct drawback in the transition zone is winter dormancy, a temporary suspension of visible growth, followed by discoloration and loss of functionality. In order to investigate the genotype/species effect in relation with agro-meteorological conditions, 10 cultivars/experimental lines were screened for their ability to extend the winter colour retention. A two years field study was conducted on mature swards and evaluated during the onset of dormancy and spring green-up using digital image analysis. For both parameters, in both years, the Authors observed a wide range of cultivar responses. Zoysia japonica genotypes in our study provided significantly shorter dormancy period than fine-leaved genotypes. In some instances, there were as much as 35 and 20 d difference between entries in respect to the winter colour retention and spring onset, respectively. The identification of genotypes with shorter dormancy than 'Meyer' (industry standard) may reduce use of cultural practices, as late-season nitrogen or iron application, normally used to extend the winter colour retention of zoysiagrass in late fall or early spring, showing different levels of success

Hormonal Regulation in Different Varieties of Chenopodium quinoa Willd. Exposed to Short Acute UV-B Irradiation

Increased ultraviolet-B (UV-B) due to global change can affect plant development and metabolism. Quinoa tolerates extreme conditions including high UV levels. However, the physiological mechanisms behind its abiotic stress tolerance are unclear, especially those related to UV-B. We previously demonstrated that 9.12 kJ m−2 d−1 may induce UV-B-specific signaling while 18.24 kJ m−2 d−1 promotes a UV-B-independent response. Here, we explored the effects of these UV-B doses on hormonal regulation linked to plant morphology and defense among diverse varieties. Changes in fluorescence parameters of photosystem II, flavonoids and hormones (indoleacetic acid (IAA), jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA)) were surveyed under controlled conditions. Here, we showed that the sensitivity to short acute UV-B doses in varieties from different habitats is influenced by their parental lines and breeding time. UV-B sensitivity does not necessarily correlate with quinoa’s geographical distribution. The role of flavonoids in the UV-B response seems to be different depending on varieties. Moreover, we found that the extent of changes in JA and SA correlate with UV-B tolerance, while the increase of ABA was mainly related to UV-B stress.Peer reviewe

Hormonal Regulation in Different Varieties of Chenopodium quinoa Willd. Exposed to Short Acute UV-B Irradiation

Increased ultraviolet-B (UV-B) due to global change can affect plant development and metabolism. Quinoa tolerates extreme conditions including high UV levels. However, the physiological mechanisms behind its abiotic stress tolerance are unclear, especially those related to UV-B. We previously demonstrated that 9.12 kJ m−2 d−1 may induce UV-B-specific signaling while 18.24 kJ m−2 d−1 promotes a UV-B-independent response. Here, we explored the effects of these UV-B doses on hormonal regulation linked to plant morphology and defense among diverse varieties. Changes in fluorescence parameters of photosystem II, flavonoids and hormones (indoleacetic acid (IAA), jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA)) were surveyed under controlled conditions. Here, we showed that the sensitivity to short acute UV-B doses in varieties from different habitats is influenced by their parental lines and breeding time. UV-B sensitivity does not necessarily correlate with quinoa’s geographical distribution. The role of flavonoids in the UV-B response seems to be different depending on varieties. Moreover, we found that the extent of changes in JA and SA correlate with UV-B tolerance, while the increase of ABA was mainly related to UV-B stress

Hormonal Regulation in Different Varieties of Chenopodium quinoa Willd. Exposed to Short Acute UV-B Irradiation

Increased ultraviolet-B (UV-B) due to global change can affect plant development and metabolism. Quinoa tolerates extreme conditions including high UV levels. However, the physiological mechanisms behind its abiotic stress tolerance are unclear, especially those related to UV-B. We previously demonstrated that 9.12 kJ m−2 d−1 may induce UV-B-specific signaling while 18.24 kJ m−2 d−1 promotes a UV-B-independent response. Here, we explored the effects of these UV-B doses on hormonal regulation linked to plant morphology and defense among diverse varieties. Changes in fluorescence parameters of photosystem II, flavonoids and hormones (indoleacetic acid (IAA), jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA)) were surveyed under controlled conditions. Here, we showed that the sensitivity to short acute UV-B doses in varieties from different habitats is influenced by their parental lines and breeding time. UV-B sensitivity does not necessarily correlate with quinoa’s geographical distribution. The role of flavonoids in the UV-B response seems to be different depending on varieties. Moreover, we found that the extent of changes in JA and SA correlate with UV-B tolerance, while the increase of ABA was mainly related to UV-B stress

Carbohydrate Metabolism During Wintering Period in Four Zoysiagrass Genotypes

A key barrier to widespread use of warm-season grasses in the transition zone between the temperate and subtropical climates is represented by the winter dormancy, a temporary suspension of visible growth of any plant structure including the meristem. In this environment, species with different photosynthetic carbon cycle coexist, leading to asynchrony in growth among warm- and cool-season grasses. The objectives of the present study were (i) to assess the carbohydrate content in four representative zoysiagrasses Zoysia japonica 'El Toro', 'Meyer', Z. pacifica, and Z. matrella 'Zeon' during three successive phases of vegetation phenology, senescence, dormancy, and green-up, and (ii) to characterize the metabolic responses to phenological variations under natural acclimation. Japanese lawn grass genotypes 'El Toro' and 'Meyer' showed longer dormancy periods than fine-leaved Z. pacifica and 'Zeon'. In Japanese lawn grass genotypes, the progressive decline of photosynthetic pigments was similar to that observed in the color retention. Over the experimental period, a significantly greater amount of starch reserves was observed in sprigs (horizontal stems) in the Japanese lawn grasses than in the fine-leaved zoysiagrasses. In general, total soluble sugars (TSS) in leaves and sprigs did not show evidence of sugar starvation during the senescence phase. TSS increased significantly during cold acclimation, resulting in a higher metabolic activity at the onset of green-up to support spring regreening in all zoysiagrasses except 'Meyer' leaves

Warm-season turfgrass species generate sports surfaces with different playability

Synthetic sports surfaces are increasingly subject to standardization of athlete-surface and ball-surface interactions (playability parameters). Such standardizations have led to an increase in the level of the engineering and predictability of these surfaces, and as such may be beneficial also for natural turf. In warm and temperate climates, many natural turf sports surfaces are established with warm-season (C4) turfgrass species due to their suitability to the environment in such areas. This study was aimed at evaluating the Féderation Internationale de Football Association (FIFA)-standard playing characteristics of different sports turf surfaces obtained from three commonly used C4 turfgrass species: 1) ‘Tifway 419’ hybrid bermudagrass (Cynodon dactylon var. dactylon × C. transvaalensis), 2) ‘Zeon’ manilagrass (Zoysia matrella), and 3) ‘Salam’ seashore paspalum (Paspalum vaginatum) for factors concerning leaf tissue (silica, lignin, water content) and canopy structure (shoot density, leaf architecture, stolon density, etc.). Results showed that surfaces of different C4 turfgrass species generate different playability parameters, with seashore paspalum being a harder faster surface, manilagrass being a softer slower surface, and hybrid bermudagrass showing intermediate characteristics. These playing quality results were associated with certain specific canopy biometrical/morphological parameters such as shoot density, horizontal stem density (HSD), leaf section, and, to a lesser extent, to certain plant tissue compounds (lignin, silica)