Golf Course Management

FEB 2019

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74 GOLF COURSE MANAGEMENT 02.19 Experimental design To assess the effects of nutrient limita - tion, two nutrient treatments were applied to all 34 genotypes (17 from putting greens and 17 from "native" habitats — that is, not from a putting green): nutrient-enriched — watered with a 30% strength of Hoagland's solution, which supplies all of the required inorganic nutrients for plants and no carbon compounds; and nutrient-deprived — watered with sterilized distilled water. Watering and nutrient application were by dropper bottles. All 34 genotype cultures were assigned to each treatment. Developmental phenological observations To assess the effects of habitat (native vs. green) and nutrient limitation, the time (days) when the following developmental events oc - curred was recorded: shoot regeneration (from protonema) and first shoot induction. (Note: A protonema — the plural is protonemata — is a thread-like chain of cells that forms the earli - est stage of the life cycle of mosses.) Life-history trait assessments To assess the effects of habitat (native vs. green) and nutrient treatment (nutrient-en - riched vs. nutrient-deprived), growth was as- sessed as: the maximum linear distance pro- tonemal filaments extended from the original planted shoot apex (in millimeters on day 21 of the experiment); the number of protonemal shoots (shoots produced directly from proto - nemal mats) on day 21; the height (in milli- meters) of the tallest shoot after five months in culture measured from media surface to shoot apex; and percent aerial rhizoid cover on day 50. Results and discussion Developmental phenology Shoot regeneration from protonema origi - nating from the original shoot axis occurred about one day earlier (day 5 vs. day 6) in geno - types from green habitats than in genotypes from native habitats, and was not affected by nutrient treatment (data not shown). Simi - larly, shoot induction occurred earlier in geno- types from green habitats but did not differ between the nutrient treatments. Allocation to life-history trait Growth was assessed through the number of protonemal shoots, shoot height and aerial rhizoid cover. Over the first 21 days of the ex - periment, protonemata from greens produced more than three times the number of shoots produced in native habitats (Figure 3), and there was no effect of nutrient treatment on shoot production. At the conclusion of the experiment (5 months), the shoots from the genotypes of green habitats were more than twice the length of the shoots from the native habitats (Figure 4). Similarly, high levels of nutrients resulted in shoots approximately two times taller than shoots produced under low- nutrient conditions (Figure 5). Among geno - types from green habitats, rhizoid cover aver- aged ~80% in the nutrient-enriched treatment when assessed on day 50 of the experiment. By contrast, among genotypes from native habi - tats, rhizoid cover was ~15% and greater in the nutrient-enriched treatment than in the low- nutrient treatment (Figure 6). Greens vs. natives In summary, silvery-thread moss collected from putting greens demonstrated diver - gent traits from those found in native habi- tats. Plants from putting greens were faster in reaching developmental time points and produced fewer specialized asexual structures (bulbils, gemmae) compared with plants from native habitats (data not shown). Further, plants from the greens regenerated protone - mata faster from detached shoot apices, and these protonemata extended laterally more rapidly from the original shoot apex than did genotypes collected from native habitats (data not shown). Shoot induction from the proto - nemal mat was quicker in plants from greens, and these colonies produced three times the number of shoots after 21 days compared with plants from native habitats (Figure 3). e tall - est shoot of colonies originating from greens was twice the height of the tallest shoot from native habitats at the conclusion of the ex - periment (150 days). e cultures from greens produced much more extensive aerial rhizoid cover than cultures from native habitats (Fig - ure 6), which could represent a trait favored in putting greens that improves competition with grasses. Unexpectedly, for germina - tion time, rhizoid cover and shoot number, genotypes from putting greens where nutri - ents were withheld exhibited more aggressive growth than genotypes from native habitats where nutrients were allowed, suggesting ad - aptation to the putting green environment. Results presented here suggest that put - ting green genotypes have been selected to be specialized on putting greens, either be - Number of shoots 35 30 25 20 15 10 5 0 Shoot number Nutrients Water Green Nutrients Water Native Figure 3. By day 21 of the experiment, the number of shoots produced by protonema was far greater for silvery-thread moss from a putting green than for silvery-thread moss from a native area under both treatments (nutrients or distilled water).

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