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- Author or Editor: Stuart L. Warren' x
- Journal of the American Society for Horticultural Science x
Fraser fir [Abies fraseri (Pursh) Poir.] and Norway spruce [Picea abies (L.) Karst.] were grown in seven vegetation management programs ranging from 100% cover of grass-dominated vegetation to bare soil on opposing north and south aspects. Concentrations of 13 nutrients were determined at three growth stages during 2 years: active terminal growth, cessation of terminal expansion, and dormancy. Aspect did not affect nutrient concentrations. Vegetation management programs bad a significant impact on nutrient concentration for both species. Nitrogen, Ca, B, Fe, and Mn concentrations during dormancy were negatively correlated with herbaceous biomass. In contrast, N during active growth and P and Mg concentrations during all stages were positively correlated with herbaceous biomass. Vegetation management only affected the seasonal trend of Mo. Seasonal trends varied by nutrient in both species.
Temperature sensitivity of net photosynthesis (PN) was evaluated among four taxa of rhododendron including Rhododendron hyperythrum Hayata, R. russatum Balf. & Forr., and plants from two populations (northern and southern provenances) of R. catawbiense Michx. Measurements were conducted on leaves at temperatures rauging from 15 to 40C. Temperature optima for PN ranged from a low of 20C for R. russatum to a high of 25C for R. hyperythrum. At 40C, PN rates for R. hyperythrum, R. catawbiense (northern provenance), R. catawbiense (southern provenance), and R. russatum were 7.8,5.7,3.5, and 0.2 μmol·m-2·s-1, respectively (LSD0.05 = 1.7). Rhododendron catawbiense from the southern provenance did not appear to have greater heat tolerance than plants from the northern provenance. Differences in dark respiration among taxa were related primarily to differences in tissue weight per unit leaf surface area. Temperature coefficients (Q5) for respiration did not vary in temperature response among taxa. Differences in heat tolerance appeared to result from a combination of stomatal and nonstomatal limitations on PN at high temperatures.
Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 mg·liter-1 to rooted stem cuttings of `Spectabilis' forsythia (Forsythia ×intermedia Zab.) potted in calcined clay. Plants were harvested 0, 40, 80, 120, and 369 days after treatment (DAT). Treatment with uniconazole at 90 to 210 mg·liter suppressed leaf area and dry weight an average of 16% and 18%, respectively, compared to the nontreated controls when averaged over all harvest periods. Stem and root dry weight suppression was greatest at 80 DAT, 47% and 37%, respectively. Uniconazole suppressed root length from 15% to 36% and root area from 15% to 33% depending on harvest date. Internode length and stem diameter of uniconazole-treated plants were suppressed at all harvests except 369 DAT. Uniconazole resulted in increased and decreased root: shoot ratios 40 and 80 DAT, respectively; while root: shoot ratios were not affected for the remainder of the study. Relative growth rates of leaves, stems, and roots decreased with increasing uniconazole concentration; however, no relative growth rates were suppressed beyond 80 DAT. Generally, mineral nutrient concentrations increased as a result of uniconazole application. The proportion of mineral nutrients allocated to leaves and roots was not affected while the proportion of nutrients allocated to stems decreased with uniconazole application compared to the controls. Chemical name used: (E)-1-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (uniconazole).
Abstract
Seven vegetation management programs ranging from 100% cover of grass-dominated vegetation to bare soil were created on opposing north and south aspects. Nutrient contents of the herbaceous vegetation and soil were effected significantly by management programs, location in the plot (row and interrow), and time. The presence or absence of vegetation influenced vegetative uptake and leaching losses, resulting in differences among the vegetation management programs. In general, the upper soil (0- to 15-cm depth) with 100% vegetative cover contained more exchangeable Mg and less NO3 and available P than under bare soil. Exchangeable Ca was not affected by the management programs. Differences in growth form (grass or forb), perennial or annual vegetation, and percent bare soil accounted for the majority of differences in the nutrient content of the noncrop vegetation. Aspect did not affect any of the plant and soil parameters measured.
Seedlings of flame azalea [Rhododendron calendulaceum (Michx.) Torr] were grown for 12 weeks under long-day conditions with days at 18, 22, 26, or 30C for 9 hours in factorial combination with nights at 14, 18, 22, or 26C for 15 hours. Total plant dry weight, top dry weight, leaf area, and dry weights of leaves, stems, and roots were influenced by day and night temperatures and their interactions. Dry matter production was lowest with nights at 14C. Root, leaf, top, and total dry weights were maximized with days at 26C in combination with nights at 18 to 26C. Stem dry weight was maximized with days at 26 to 30C and nights at 22C. Leaf area was largest with days at 18 and 26C in combination with nights at 18 or 26C. Within the optimal, day/night temperature range of 26 C/18-26C for total plant dry weight, there was no evidence that alternating temperatures enhanced growth. Shoot: root ratios (top dry weight: root dry weight) were highest with days at 18 and 30C. Leaf area ratio (total leaf area: total plant dry weight) was highest and specific leaf area (total leaf area: leaf dry weight) was largest when days and nights were at 18C and were lower at higher temperatures. Regardless of day/night temperature, leaf weight ratio (leaf dry weight: total plant dry weight) was higher than either the stem weight ratio (stem dry weight: total plant dry weight) or root weight ratio (root dry weight: total plant dry weight). Net leaf photosynthetic rate increased with day temperatures up to 30C.
Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 ppm to rooted stem cuttings of `Spectabilis' forsythia (Forsythia xintermedia Zab.) potted in calcined clay. Uniconazole resulted in higher total leaf chlorophyll (chlorophyll + chlorophyll,) concentration and a decreased ratio of chlorophyll a: b. Stomata1 density of the most recently matured leaves increased linearly with increasing uniconazole concentration 40, 60, and 100 days after treatment (DAT). The number of stomata per leaf (stomata1 index) increased linearly with increasing concentration of uniconazole throughout the initial 100 DAT. Uniconazole suppressed stomata1 length at all sampling dates and the level of suppression increased with increasing concentration of uniconazole from 20 to 100 DAT. Stomata1 width was suppressed by uniconazole at 40 DAT. Leaves developed after uniconazole application had higher levels of net photosynthesis when measured 55, 77, and 365 DAT. Stomata1 conductance for uniconazole-treated plants was higher compared to nontreated control (0 mg·liter-1) plants when measured 49, 55, 77, and 365 DAT. Initiation of secondary xylem for stem tissues of uniconazole-treated plants was suppressed and expansion of xylem vessel length and width was less. Secondary phloem tissues of stems from uniconazole-treated plants contained larger numbers of phloem fibers having smaller cross sectional areas than phloem fibers of controls. Chemical name used: (E)-1-(p-Chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-01 (uniconazole).
Seedlings of mountain laurel (Kalmia latifolia L.) were grown for 16 weeks under long-day conditions with days at 18, 22, 26, or 30C for 9 hours in factorial combination with nights at 14, 18, 22, or 26C for 15 hours. Total plant dry weight, top dry weight, and dry weights of leaves, stems, and roots were influenced by day and night temperatures. The night optimum for all dry weight categories was 22C. Dry matter production was lowest with nights at 14C. Total plant dry weight and dry weights of tops, leaves, and stems were maximized with days at 26C, but for roots the optimum was 22C. Dry weight accumulation was lower with days at 18 or 30C. Responses of leaf area were similar to that of total plant dry weight, with optimum days and nights at 26 and 22C, respectively. Within the optimal day/night temperature range of 22-26/22C for dry weights, there was no evidence that alternating temperatures enhanced growth. Shoot: root ratios (top dry weight: root dry weight) increased with day temperatures up to 30C and were highest with nights at 14 or 26C. Leaf weight ratio (leaf dry weight: total plant dry weight) decreased with increasing night temperature, and increased curvilinearly in response to day temperature with the minimum at 26C. Stem weight ratio (stem dry weight: total plant dry weight) increased with increasing day or night temperature. Root weight ratio (root dry weight: total plant dry weight) was highest with nights at 18 or 22C and decreased with days >22C. Net leaf photosynthetic rate was maximized with days at 26C.
Abstract
Seven vegetation management programs ranging from 100% cover of grass-dominated vegetation to bare soil were created on opposing north and south aspects. After 3 years, fraser fir [Abies fraseri (Pursh) Poir.] survival had decreased when grown in bare soil, compared to survival in the other management programs. Norway spruce [Picea abies (L.) Karst.] survival was not affected by the management programs. Maximum stem diameter and root growth of Norway spruce were obtained with a bare row regardless of the interrow vegetation. Root growth in fraser fir was similar to spruce, but bare soil was required for maximum stem diameter growth. Height growth in both species was affected little by treatment. Stem diameter and root growth were negatively correlated with above-ground herbaceous biomass in the row. Forbs interfered less than grasses with fraser fir and Norway spruce diameter growth. Norway spruce growth was not affected by aspect, but fraser fir was larger (height and stem diameter) on the south aspect when grown in bare soil.