Bermudagrass (Cynodon sp.) greens are overseeded annually with rough bluegrass (Poa trivialis L.) in the coastal southeastern United States, where irrigation water is often saline. Salinity may slow seed germination and delay turf establishment. Cultivar and seed lot differences in sensitivity to salinity may be substantial. Our objective was to determine the effects of salinity on germination of commercially available rough bluegrass cultivars and seed lots. To accomplish this, we examined the effects of salinity (0, 1.8, 3.4, and 5.0 dS·m-1 established with NaCl in deionized water) on germination of 33 cultivars/seed lots of rough bluegrass in vitro. Fifty seeds of each cultivar/seed lot were placed on pre-moistened germination paper in petri dishes, sealed with parafilm, and placed in growth chambers with 12-hours light/12-hours dark at 20/10 °C, respectively. Germination was scored from 4 to 25 days after seed placement. Rough bluegrass germination rate varied among cultivars/seed lots, ranging from less than three seeds/day to nearly seven seeds/day. Salinity slowed rough bluegrass germination rate from about six seeds/day at 0 dS·m-1 to five seeds/day at 5 dS·m-1. Increasing salinity reduced early germination of some cultivar/seed lots more than that of others. Impact was substantial in three cultivar/seed lots, where early germination at 5.0 dS·m-1 was less than 15% of that at 0 dS·m-1. For most cultivar/seed lots, the reduction in early germination with salinity at 5.0 dS·m-1 was about 50% of that at 0 dS·m-1. Final germination was reduced only 3% by increasing salinity. In view of differences in germination rate and response to salinity among seed lots of rough bluegrass cultivars, we suggest the planting of multiple cultivars and seed lots of rough bluegrass to insure rapid establishment.
project include Donald Avery, Vanessa Lampke, Jennifer Martin, Jim Murray, Kim Turner, and Jessica Picucci. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby
In vitro germination of freshly collected pollen and pollen stored 1, 10, 11, 12, and 13 years in liquid nitrogen was examined for `Desirable' pecan [Carya illinoinensis (Wangenh.) C. Koch]. Viability of pollen stored in liquid nitrogen for 1, 10, 11, 12, and 13 years was not diminished in comparison to that of fresh pollen. Morphology of stored pollen grains and the germ tube was normal. Thus, liquid nitrogen may offer a means of haploid preservation of pecan.
Osmotic agents used to prevent apple pollen grain germination were studied in vitro by applying 10 μL of solutions to germinating apple pollen on germinating and growth media. Seven concentrations (0%, 0.25%, 0.5%, 1%, 2%, 5% and 10%) of the solution were prepared for each chemical and the characteristics of pH, EC, and osmotic potential were measured. Apple pollen was dispersed onto the media in petri dishes. Micro drops of solution were then applied to marked areas. Dishes were then placed in germination cabinets at 25 °C. Cumulative percentage pollen germination was calculated 4, 8, 12, and 24 h after treatment by microscopic observation. Generally, the cumulative percentage pollen germination decreased asymptotically with increasing chemical concentration. The most effective chemicals for restricting pollen germination and growth were CuSO4 (0.25%), CH3 COOH (0.25%), CaCl2 (10%), K2 S2 O5 (0.25%), Methyl Jasmonate (2%). The effect of these chemicals has also been tested on pistil viability both in vitro and on excised limbs.
The effects of high-temperature stress on pollen viability and in vitro and in vivo germinability were studied in two facultative, short-day strawberries (Fragaria ×ananassa Duch.), `Nyoho' and `Toyonoka.' Plants were exposed to two day/night temperature regimes of either 23 °C/18 °C (control) or 30 °C/25 °C (high temperature) from when the first inflorescence became visible until anthesis. Pollen viability in `Nyoho' was only slightly affected at 30 °C/25 °C when compared with pollen from plants grown at 23 °C/18 °C. In `Toyonoka', however, pollen viability was significantly lower at 30 °C/25 °C than at 23 °C/18 °C. The in vitro germination percentages were significantly lower in pollen from plants grown at 30 °C/25 °C and germinated at 30 °C than from plants grown at 23 °C/18 °C and germinated at 23 °C in both cultivars. But the percentages were much lower in `Toyonoka' than in `Nyoho', particularly at the 30 °C germination temperature. Pollen from plants grown at 23 °C/18 °C also extended longer pollen tubes than pollen grown at 30 °C/25 °C in both cultivars, but `Nyoho' had longer pollen tubes than `Toyonoka' at 30 °C/25 °C. Fluorescence microscopy revealed that most of the `Nyoho' pollen germinated on the stamen, elongated through the style and reached the ovule regardless of temperature treatment. In `Toyonoka', pollen germination and elongation were greatly inhibited at 30 °C/25 °C, resulting in unfertilized ovules. These results suggest that certain strawberry cultivars produce heat-tolerant pollen, which in turn could result in higher fruit set.
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Kiwifruit (Actinidia deliciosa) is a functionally dioecious plant where fruit size is dependent on number of seeds set. Pollen fertility was estimated in 1990 and 1991 by percentage stainability and percentage germinability in vitro. Profiles of the isozymes AAT, GPI and PGM were used to assess if any large differences in pollen fertility could be attributed to genotypic variation. Based on these three isozymes, eight different genotypes were discovered. Although significant differences were found among vines within orchards and among orchards, all vines can be considered good pollenizers (stainability > 87%). A positive correlation was found in 1991 between percentage stainability and percentage germination.
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The genus Aesculus (buckeyes and/or horsechestnuts) is composed of 13 species and a number of interspecific hybrids. Pollen from 11 genotypes from five Aesculus species and the hybrid Aesculus ×carnea were used to develop an in-vitro germination test to evaluate pollen viability under various storage treatments. This test was optimized using samples of both fresh pollen and pollen that had been stored up to 1 year. The most effective medium contained 20% sucrose, 100 mg·L-1 H2BO3, 150 mg·L-1 Ca(NO3)2, and 1% agar. The highest germination percentage was observed at 15 °C across all storage treatments. Fresh pollen germinated in excess of 80% over a wide range of germination temperatures. Based on this, all specimens studied would be good pollen parents. The differences in pollen germination between storage at -20 and -80 °C were nonsignificant, but the duration of the storage period was highly significant. At 3 months, viability remained above 60% for four of the six species/hybrid tested. However, at 12 months, all pollen tested dropped below the threshold for good fruit set based on in-vitro pollen germination. Based on these observations, short-term pollen storage may permit crosses between parents with temporally separate flowering phenologies. However, conventional storage procedures are inadequate to maintain pollen collected from a male parent for crosses in subsequent growing seasons.