Are Mycorrhiza Always Beneficial?

In this work we evaluate whether the effect of ectomycorrhiza in the early developmental stages of symbiosis establishment is detrimental or beneficial to plant productivity and whether this effect is dependent on either N nutrition or plant age. Groups of Pinus pinaster L. plants with different ages and nutritional status were inoculated with alive or dead Pisolithus tinctorius. The plants were fed with either 1.9 mM or 3.8 mM ammonium as N source. Ectomycorrhiza establishment was monitored until 1 month after the inoculation through daily chlorophyll a fluorescence measurements and the analysis of fast fluorescence kinetics O-J-I-P, biomass increment and photosynthesis. Our results show that plants react differently to ectomycorrhiza formation depending on their age (stage of development, leaf area), their initial nutritional status, and the amount of nitrogen supplied. Mycorrhiza formation was found to constitute a stress depending on the plants’ age. Increased availability of N softened or eliminated the negative impact of mycorrhiza formation. Only younger plants eventually developed a higher net photosynthesis rate when mycorrhizal. It is concluded that ectomycorrhiza formation may have a detrimental rather than a beneficial effect on plants’ productivity during their establishment and early developmental stages, and that this depends on the amount of N available to the plant, on the nutritional status and on the age of the plant. Chlorophyll a fluorescence measurements proved to be a non-destructive, non-invasive and reliable tool able to identify the first signals of plant-mycorrhiza fungi interactions.     

Easy projection of stereo movies

A method is described of showing colour stereo movies with arbitrary movie projectors by means of a small portable adapter. The beam from an ordinary movie projector is passed through a linear polarizer and then a crystal, which rotates the angle of polarization under voltage control so that alternating left and right images are polarized 90° apart. A photodiode and a sensing circuit synchronize the polarization shift to the flicker of the projector shutter. The adapter is small and self contained and needs only to be placed in the path of the projected beam.     

Mycorrhiza and root-associated fungi in Spitsbergen

Summary Roots of 76 plant species collected in West Spitsbergen (Svalbard), in the middle-northern Arctic zone, were examined for mycorrhiza and root-associated fungi. Dryas octopetala, Pedicularis dasyantha and Salix polaris were ectomycorrhizal and Cassiope tetragona and Empetrum hermaphroditum ericoid mycorrhizal. Pedicularis dasyantha was only slightly infected. Structures resembling vesicular-arbuscular mycorrhizal (VAM) fungi were not found in the roots, and soil samples screened for VAM fungi contained only one spore. Root endophytic fungi commonly occurred in Spits-bergen, but only Olpidium brassicae, Pleospora herbarum, Papulaspora, Microdochium bolleyi and Rhizoctonia solani were identified with reasonable certainty. A sterile endophytic dark-septate fungus (DSF) was in 39.5% of the flowering-plant species examined, especially in the Brassicaceae, Caryophyllaceae, Saxifragaceae and Poaceae. DSF were categorized into four slightly overlapping groups. Sterile endophytic hyaline septate fungi were rare. In the literature it is suggested that at least some of the DSF species or the hyaline septate fungi are functionally mutualistic rather than saprophytic or pathogenic. The literature on ectomycorrhizal fungi and plants in Spitsbergen is reviewed, including about 50 species, mainly of the genera Cortinarius, Hebeloma, Inocybe, Laccaria, Lactarius and Russula. These are symbiotic with the above-mentioned ectomycorrhizal plants. Four further ectomycorrhizal plants (Betula nana, Salix spp.) are very rare in the area.     

Mycorrhiza in floriculture: difficulties and opportunities

Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with the roots of about 80% of plant species. The arbuscular mycorrhizal (AM) symbiosis benefits the growth and development of plants, among them a variety of ornamental horticulture (floriculture) plants. AMF have been shown to benefit plants that suffer from stunted growth, including that stemming from abiotic stress. Many floriculture crops are grown in the semi-arid environment of the Mediterranean region, and therefore AMF application may be implemented in floriculture practices to significantly promote crop growth and yield. However, for successful commercial utilization of the AM symbiosis and its introduction into ornamental floriculture practices, several considerations must be taken into account. These are highlighted and examined in the present review. They include the prerequisite of availability of high quantities of good-quality AMF inocula, the need to use different types and dosages of AMF inocula, at different times of inoculation, and the agricultural crop growth practices that are best-suited for integration with AMF inoculation. The difficulties and opportunities in AMF usage in floriculture are discussed and suggestions on different ways to solve the encountered difficulties are made, to promote cost-effective use of AMF in floriculture.