Information is lacking regarding the changes of endogenous soluble carbohydrates of saltgrass [Distichlis spicata (L.) Greene] during cold acclimation. The objective of this study was to quantify soluble carbohydrates and their relationships to freezing tolerance in six saltgrass accessions (A65, A29, C66, 32, 55, and 48). The study was performed at monthly intervals under natural acclimation in two consecutive winter seasons (October 1999–April 2000 and October 2000–April 2001) at Fort Collins, CO. Concurrent with LT50 (subfreezing temperature resulting in 50% mortality) assessment, soluble carbohydrates, including sucrose, fructose, glucose, raffinose, and stachyose were measured by gas chromatography (GC). Results indicated significant differences among accessions and sampling dates in LT50 and carbohydrate content. Sucrose was the predominant sugar, but did not show a clear seasonal trend and had no correlation with freezing tolerance. Fructose, glucose, raffinose, and stachyose exhibited clear seasonal changes, reaching highest concentrations during midwinter. In December of both seasons, higher concentration of fructose and glucose were observed in 48 and 55 as compared with other accessions. Accession A29 had the highest concentration of raffinose in December and January in both seasons. A29 also had the highest stachyose content in midwinter of 1999‐2000. Higher fructose, glucose, or raffinose concentrations were frequently observed in accessions of 48, 55, and A29, which coincided with their lower LT50 as compared with the other accessions. In contrast, C66 had the lowest sugar concentrations, which related to its sensitivity to low temperatures. These results indicate that fructose, glucose, raffinose, and stachyose may play important roles in saltgrass freezing tolerance.
Polyethylene glycol was added to the rooting medium of micropropagatedgrape shoots to induce water stress. At the end of the rooting stage, plantlets treated with 2% polyethylene glycol were compared with untreated control plantlets and greenhouse-grown plants. Leaves of treated plantlets had the highest deposition of epicuticular wax, followed by those of the greenhouse and control. Stomatal index did not vary among treatments. However, differences in leaf epidermal cell configuration were observed among treatments. The morphological changes of treated plantlets, including substantial deposition of epicuticular wax and modified leaf surface anatomy were associated with increased ex vitro survival after four weeks in the greenhouse.
Freezing tolerance is an environmental adaptation that significantly influences plant geographical distribution. Since differences in winter survival among saltgrass ecotypes have been observed in the field at Fort Collins, CO, the objective of this study was to determine the relative freezing tolerance, seasonal changes in the freezing tolerance, and winter survival of six accessions of saltgrass [Distichlis spicata var. stricta (L.) Greene]. Saltgrass accessions A65 and A29 were originally collected from Denver, CO, while C66 was from Humbolt Sink, NV, 32 from Wanship, UT, 55 from Hereford and 48 from Farmingdale, SD. These accessions were established in a field nursery at Fort Collins, CO. Rhizomes were sampled at monthly intervals from October 1999 through April 2000 and from October 2000 through April 2001 and subjected to laboratory freezing tests. Cold hardiness of the saltgrass accessions increased gradually during the fall with maximum hardiness occurring at midwinter. During midwinter, freezing tolerance was significantly different among accessions. Ranking of accessions for subfreezing temperature resulting in 50% mortality [LT50 (°C)] during January 2000 was A29 = 48 (−20.0) < 55 (−17.0) ≤ 32 (−15.5) ≤ A65 = C66 (−14.0). In January 2001, they were ranked with 48 = 55 (−26.0) < A65 = 32 (−23.0) < A29 (−20.0) = C66 (−18.5). In December and January sampling dates of the first season, accessions A29, 48, and 55 exhibited the highest relative regrowth when exposed to temperatures ≈ −20.0°C. In midwinter of the second season, accession 55 showed the highest regrowth after being subjected to temperatures ≈ −25.0°C. Accession C66 had the lowest regrowth potential after freezing treatments in both seasons. Winter survival in the field correlated negatively with LT50 value, with accessions 48, A29, and 55 demonstrating greater winter survival while C66 had the lowest percentage survival. The difference in freezing tolerance among accessions is in part associated with their origin‐inherited adaptation. This information is useful for defining the potential adaptation range of saltgrass and in saltgrass breeding projects to select and develop freezing tolerant saltgrass.
Relationships between current sc8son pknt production 8nd pknt mwsurcmcnts (crown width 8nd volume) were lnvcstlg8tcd for 4 South Texas shrubs collected during July, 1978. Shrubs lnvcstlg8tcd were bkckbrush (&a& &&fu&), gtmjlllo (A. bcriimdieri), shrubby blue srgc (S&&t ballotaqffora), and kidney wood (Eysenhmdtia texunu). R~iom of production 8v8ikbk to whltc-t8lkd deer on both crown width 8nd crown volume ykldcd cocfflcitnts of dctcrmbutlon of 25~37%. Log-log 8nd qtmdrrtlc cqtmtions provided bcttcr results th8n llnur, log8rlthmlc, or cxponcntkl cqu8tlons. One piant mc8suremcnt (m8xlmum crown width 8s M independent v8rkblc) produced results com-p8nbk to those from crown volume. R8ngt site (sandy lorm or gr8y sandy lorm) did not rffcct pknt productlompknt mcesurements rcktlonshlps, but mcch8nlal trertment (shrcddlng) did. Sclcctlng pknts reprcscntlng the full r8ngc of shrub sh8pcs 8nd sizes is critk8l to the proper use of this method, l d trutments which grc8tly modify piant fonn wiii probably require rcgrcssion quations scpar8tc from thoac for undisturbed vegetation.
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