Consider the characteristics of moss and fern life cycles.
Which of the following sets of statements is true?
In mosses, the gametophyte is the dominant stage of the life cycle; in ferns, the sporophyte is the dominant stage of the life cycle. Ferns require moisture for sperm to reach the egg, but mosses do not.
In mosses, the sporophyte is the dominant stage of the life cycle; in ferns, the gametophyte is the dominant stage of the life cycle. In both mosses and ferns, moisture is required for sperm to reach the egg.
The gametophyte is the dominant stage of the life cycle in both mosses and ferns. Mosses require moisture for sperm to reach the egg, but ferns do not.
In mosses, the gametophyte is the dominant stage of the life cycle; in ferns, the sporophyte is the dominant stage of the life cycle. In both mosses and ferns, moisture is required for sperm to reach the egg.
The gametophyte is the dominant stage of the life cycle in both mosses and ferns. In both mosses and ferns, moisture is required for sperm to reach the egg.
MB 2 - Chapters 31-33Due: 8:00am on Wednesday, January 28, 2015You will receive no credit for items you complete after the assignment is due. Grading PolicyItem 1Can mycorrhizae help plants cope with high-temperature soils?The great majority of vascular plant species benefit from underground associations with mycorrhizal fungi. The branching hyphae of arbuscular mycorrhizal(AM) fungi extend through the cell walls of host plants, bringing water and inorganic nutrients into the plant roots in exchange for sugars. Researchersinvestigated the role of AM fungi in the growth of Dichanthelium lanuginosum, a grass that grows only in the high temperature thermal soils found in volcanicallyactive areas. Rooting zone temperatures in thermal soils are 45C or above.The researchers collected D. lanuginosumseeds from geothermal areas of Yellowstone National Park. After the seeds germinated, 27 seedlings weretransferred to a greenhouse, where they were grown in heated pots. Temperatures in the pots mimicked conditions in thermal soils, ranging from 30C at thesoil surface to 50C at the base of the pot.The pots were divided into three treatment groups:Nine pots were notinoculated with AM fungi.Nine pots were inoculated with nonthermalAM fungi (fungi collected from grassland soil).Nine pots were inoculated with thermalAM fungi (fungi collected from high-temperature geothermal areas of Yellowstone National Park).All seedlings received the same amount of light and water. After 80 days, the researchers harvested all plants, dried and weighed the shoots, and measured thetotal length and diameter of the roots.The bar graph shows the mean dry weight of shoots in each treatment group.The table shows the mean total root length and mean root diameter of plants ineach treatment group.Mean total root length (cm)Mean root diameter (mm)No AM fungi1,8000.19Nonthermal AM fungi4,8000.23Thermal AM fungi4,3000.22Part A - Interpreting the dataConsider the results shown in Figure 1 and the table.How do AM fungi affect D. lanuginosumplants grown at high temperatures?ANSWER:CorrectPart BHow do thermal and nonthermal AM fungi affect D. lanuginosumplants grown at high temperatures?∘∘∘D. lanuginosumplants show decreased shoot and root growth in pots inoculated with AM fungi.D. lanuginosumplants show similar shoot and root growth in pots with and without AM fungi.D. lanuginosumplants show increased shoot and root growth in pots inoculated with AM fungi.
. 2009 May;90(5):1378-88.
doi: 10.1890/07-2080.1.
Affiliations
- PMID: 19537557
- DOI: 10.1890/07-2080.1
Arbuscular mycorrhizal fungi ameliorate temperature stress in thermophilic plants
Rebecca Bunn et al. Ecology. 2009 May.
Abstract
Biotic interactions can affect the distribution of species across environmental gradients, and as air and soil temperatures increase, plant community response may depend on interactions with symbionts. We measured the effect of elevated soil temperatures on mycorrhizal function and on the response of both plant and fungal symbionts, using fungal inoculum isolated from either high-temperature thermal or nonthermal grassland soils. Our source for thermal soils was Yellowstone National Park, USA, where plants experience rooting zone temperatures of 45 degrees C or more. In the greenhouse, we grew three plant species (Dichanthelium lanuginosum, Agrostis scabra, and Mimulus guttatus) with three arbuscular mycorrhizal fungal (AMF) treatments (no AMF, nonthermal AMF, thermal AMF) and two soil temperatures (ambient, elevated). Biomass of the facultative thermal plants Agrostis scabra and Mimulus guttatus decreased by 50% in elevated-temperature soils, and AMF had no effect on measured plant traits. In contrast, the biomass and total root length of the obligate thermal plant Dichanthelium lanuginosum were greater at elevated soil temperatures, but only when mycorrhizal. Both mycorrhizal colonization levels and length of extraradical hyphae (ERH) increased with soil temperature across all host species. The source of the AMF inoculum, on the other hand, did not affect colonization level, ERH length, host plant biomass, or flowering for all host species in either temperature treatment, suggesting that AMF from thermal soils are not specifically adapted to higher temperatures. In the field we collected soil cores to measure in situ depth distributions of D. lanuginosum roots and ERH, and to determine which AMF species were active in plants growing in thermal soils. Roots were limited to soils with an average temperature < or =30 degrees C, while ERH existed in the hottest soils we sampled, averaging 35 degrees C. Molecular analyses of roots indicated that thermal AMF communities were composed of both generalist and possibly unique fungal species. The increase in host plant allocation to AMF, apparent lack of temperature adaptation by AMF, and differential host response to AMF suggest that AMF could be significant drivers of plant community response to increased soil temperature associated with global change.
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