The impact of mild drought stress (3 weeks at 40 % field water capacity) on yield, physiological processes, accumulation of proline and phenolic compounds and forage quality parameters in forage grasses was evaluated in pot experiments. During four different growing periods, the effects of water deficit were assessed in nine varieties from five species (Lolium perenne, Lolium multiflorum, Festuca pratensis, Festuca arundinacea and Festulolium braunii). All measured parameters were affected by drought stress in the different cuts. Photosynthesis, transpiration rate, stomatal conductance and dry matter yield were significantly lower in drought stress than under well‐watered conditions in all varieties. Higher water‐use efficiency was only observed during the first and fourth drought period, while this was not the case in the second and third. Mild drought stress significantly increased the content of proline, phenolic acid, flavonoids, water‐soluble carbohydrates and protein. All tested grasses showed also an increase of organic matter digestibility and cell wall digestibility under drought stress conditions. 相似文献
The use of saline waters is an option for the irrigation of salt tolerant ornamentals as competition for high quality water increases. However, despite the importance of ornamental shrubs in Mediterranean areas, salt tolerance of such species has received little attention. The aims of our investigation were to quantify the growth response and any injury symptom of 12 widely cultivated ornamental shrubs to irrigation with saline water and to investigate any possible relation with the concentration of Na+ and Cl− in the plants. Species were irrigated with different salinities (10, 40, and 70 mM NaCl) for a 120-day period. At the end of salt treatment, plants were sampled and dry biomass recorded; the relative growth rate (RGR) was also calculated. Root and leaf samples from each species were used to evaluate Na+, K+ and Cl− concentrations. Growth rates were significantly reduced in Cotoneaster lacteus, Grevillea juniperina and Pyracantha ‘Harlequin’, which also showed the highest percentage of necrotic leaves. The increasing external NaCl lead to an increase of Na+ and Cl− in roots and leaves of the different species, although less Na+ was accumulated than Cl−: growth reduction well correlated with the concentration of Cl− and/or Na+ in the leaves. The most sensitive species (i.e. C. lacteus, G. juniperina and Pyracantha ‘Harlequin’) had high concentrations of Na+ and/or Cl− in their leaves and also showed a decrease in their leaf K+/Na+ ratios. Even though other species (i.e. Bougainvillea glabra, Ceanothus thyrsiflorus,Leptospermum scoparium, Leucophyllum frutescens and Ruttya fruticosa) demonstrated a high ion concentration in their leaves, they could be considered relatively salt tolerant as there was little growth reduction and few symptoms of injury in the leaves. In some other cases (i.e. Cestrum fasciculatum, Escallonia rubra and Viburnum lucidum) the observed tolerance was related to higher ion concentration in the roots compared to the leaves, probably indicative of a limited transport to the shoots. Only in Eugenia myrtifolia was the absence of symptoms associated with a limited Na+ and Cl− uptake from the rhizosphere. 相似文献
Labor costs of guppy growers and breeders are largely those of manual sorting (by strain, quality and gender) and counting fish. In most farms, female and male fish are grown together and sold either separately or together. Sorting fish according to gender is important for marketing as well as for breeding programs, so that a device for sorting and counting fish can potentially reduce production costs and improve quality.
A project aiming to develop sorting and counting technologies for ornamental fish growers included development and testing of image-processing algorithms for sorting guppy fish (Poecilia reticulata) by gender. The algorithms are derived from shape and color differences between female and male guppies. An algorithm for the determination of landmarks on fish contours was developed and found to be accurate in accordance with human judgment, enabling extraction of specific shape and color features of the tail and the body.
The algorithms were applied to three sets of images of guppies of the “Red-Blond” strain. Gender identification accuracy was approximately 90% using shape features, approximately 96% using color features and was slightly improved when both color and shape features were used.
Some of the components used are essential for future development of a computer vision based system for sorting and grading ornamental fish by strain and quality. 相似文献
We tested the inter‐specific variability in the ability of three dominant grasses of temperate grasslands to take up organic nitrogen (N) in the form of amino acids in soils of differing fertility. Amino acid uptake was determined by injecting dual labeled glycine‐2‐13C‐15N into the soil, and then measuring the enrichment of both 13C and 15N in plant tissue after 50 hours. We found enrichment of both 13C and 15N in root and shoot material of all species in both soils, providing first evidence for direct uptake of glycine. We show that there was considerable inter‐specific variability in amino acid uptake in the low fertility soil. Here, direct uptake of amino acid was greater in the grass Agrostis capillaris, which typically dominates low fertility grassland, than Lolium perenne, which inhabits more fertile sites. Direct uptake of amino acid for Holcus lanatus. was intermediate between the above two species. Unlike in the low fertility soil, there was no difference in uptake of either 13C or 15N by grasses in the high fertility soil, where uptake of mineral N is thought to be the major mechanism of N uptake of these grasses. Overall, our findings may contribute to our understanding of differences in competitive interactions between grasses in soils of different fertility status. 相似文献