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Tall fescue photomorphogenesis as influenced by changes in the spectral composition and light intensity.

DECIDUOUS TREE CANOPIES significantly alter the spectral composition and PPF of solar radiation available to plants in shade. PPF in the shade of fully leafed trees can be reduced to 1 to 5% full sunlight and this significantly affects plant growth and development (Shirley, 1945). Common cool-season turfgrass species, such as Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall rescue (Festuca arundinacea Schreb.), exhibit more upright growth habits, thinner and longer leaves, shallow root systems, lower plant carbohydrate levels, reduced tillering, and decreased stand density when grown in shade (Dudeck and Peacock, 1992). Although a number of factors, such as tree root competition, may contribute to decline of turfgrass quality in shade, two of the most influential are the reduction of PPF and R:FR ratio occurring under vegetative canopies. R:FR is the ratio of the photon flux ratio of light in the 10-rim band around 660 nm to light around 730 nm.

Reduction of PPF alters the plant's photosynthetic-respiratory balance resulting in lower carbohydrate levels compared to grasses grown in open sun (Blackman and Templemen, 1940). Carbohydrate allocation favors shoot growth over root development (Dudeck and Peacock, 1992). The reduction in carbohydrate levels results in reduced tillering and stand density. Changes in PPF initiate altered leaf size and structure, chloroplast ultra-structure, and photosynthetic and respiratory metabolism (Smith, 1982).

Plant perception of the R:FR ratio is an important aspect of shade acclimation (Holmes and Smith, 1975). Changes in R:FR ratio influence plant development by altering phytochrome equilibrium. Responses to low R:FR ratio include increased stem elongation, reduced leaf area, reduced branching/tillering, and changes in chlorophyll content (Dudeck and Peacock, 1992).

The effects of foliage shade on the spectral composition, and in particular, the R:FR ratio of light has been well documented (Federer and Tanner, 1966; Vezina and Boulter, 1966). Tree leaves alter R:FR ratio of light by selectively attenuating red and blue quanta while transmitting far-red. Both deciduous and coniferous canopies filter significant amounts of red and blue quanta relative to building shade (Bell et al., 2000). Holmes and Smith (1977) found the R:FR ratio of sunlight, irrespective of time of year and weather, to be nearly constant, averaging 1.15. Reported R:FR ratios in deciduous foliage shade range from 0.36 to 0.97 (Goodfellow and Barkham, 1974). Bell et al. (2000) reported R:FR ratios of 0.91 and 0.80 for deciduous and coniferous shade, respectively.

The light compensation point of most turfgrasses is around 2 to 5% full sunlight (Beard, 1973). The most common procedure for mitigating vegetative shade problems has been removal of tree limbs. Changes in R:FR ratios alter plant development before any serious reduction in light intercepted per plant is detectable (Ballare et al., 1987). As a result, "shade-avoidance" symptoms in turf may occur under shade environments despite adequate levels of PPF and this could divert resources that would otherwise be used for more agriculturally productive activity, such as root and leaf growth (Ballare et al., 1997).

Minimal turfgrass research has focused on the influence of altered R:FR ratios under shaded environments and their impacts on turfgrass physiology. Neutral density shade fabrics are often used in shade research for ease of use and manipulation of light intensity. These materials do not alter the spectral composition of vegetative shade light and therefore do not accurately reproduce the natural foliage shade environment. A significant amount of shade research has underestimated the extent and array of developmental responses to foliage shade (Buisson and Lee, 1993). Knowledge of plant development in shade would therefore be improved by understanding the relative contributions of PPF and R:FR ratios to turfgrass photomorphogenesis. The objective of this research was to investigate the effects of altered R:FR ratios and PPF on chlorophyll content, leaf and chloroplast development, tillering, and root mass of tall fescue.

MATERIALS AND METHODS

The study was initiated on 15 June 2001 and concluded on 26 Jan. 2003 at the Ohio Turfgrass Foundation Research and Education Facility, Columbus, OH. Plots were constructed by excavating to a 30-cm root zone depth and backfilling with a 90% sand and 10% peat (v/v) mixture overtop an existing native clay loam soil. Replicate studies consisting of three 5.8- x 4.0-m main plots was established in full sun, deciduous tree shade (an east to west running row of mature hardwoods, primarily Acer spp. and Fraxinus spp. that are 20-25 m in height), and neutral density shade of a fiberglass shade structure. The fiberglass panels were mounted on a frame approximately 3 m above the turf. Panels were removed in the fall to coincide with leaf drop in the deciduous shade plots. Treatment plots were established in full sunlight and shade. Full sunlight (FS) plots received high PPF and high R:FR ratio characteristic of natural daylight while neutral shade (NS) and deciduous shade (DS) plots received similar PPF (7 and 8% of full sun, respectively) but different R:FR ratios (Table 1).

Photosynthetic photon flux was measured continuously from 15 June 2002 through 26 Jan. 2003. Cosine corrected PAR light sensors (Spectrum Technologies, Plainfield, IL) were mounted to a pole 30 cm above the soil surface and positioned in the center of each main plot. PPF was measured every 15 min and the cumulative data stored using a Spectrum Technology data logger and average daily total PPF (mol [m.sup.-2] [d.sup.-1]) was determined by Specware software (Spectrum Technologies).

Within each main plot were six 1.5- x 1.5-m subplots. Two cultivars of tall fescue, 'Plantation' (Pennington Seed, Madison, GA), and 'Equinox' (Turf Merchants, Inc., Tangent, OR) were established by seed on 28 June 2001 at a rate of 29.3 g [m.sup.-2]. The cultivars were chosen for their differences in subjective evaluation of shade tolerance (Plantation = high, Equinox = low) as reported in the results of a three-year dense shade study (NTEP, Beltsville, MD).

Rainfall was monitored and differential irrigation was provided to each of the light treatment plots to compensate for plot-to-plot differences in the amount of water received. The perimeter of the deciduous foliage shade plots was root pruned to 30-cm depth monthly to prevent encroachment of tree roots.

An 18-3-18 granular fertilizer (United Horticultural Supply, Maumee, OH) was applied at 24 kg N [ha.sup.-1] monthly from April through October (excluding July) during each season of the study. A granular application of dithiopyr [3,5-pyridinedicarbothioic acid, 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,S-dimethyl ester] was made in early April of 2001 and 2002 to suppress annual weeds. Preventative fungicide spray applications of propiconazole [1-((2-(2,4-dichlorophenyl)-4-propyl-11,3-dioxolan-2-yl) methyl)-1H-1,2,4-triazole] were made on a monthly basis throughout the growing season. Mefenoxam [(R)-2-((2,6-dimethylphenyl)-methoxyacetylamino)-propionic acid methyl ester] was applied in July of both years for prevention of Pythium spp. disease. Plots were mowed at the same time as needed with a rotary push mower to a height of 7.62 cm and the clippings collected.

Plant samples were collected for analysis of the various physiological and morphological parameters in September of 2001 and 2002. No sampling occurred within 10 cm of the plot borders. Chlorophyll content of the newest fully expanded leaf blades of five random plants in each subplot was determined by the method of Moran and Porath (1980). A 3-mm diameter disk was removed from the center of each leaf and placed in 5 mL of N,N-dimethylformamide in the dark at 4[degrees]C for 72 h. For leaves with widths less than 3 mm, 1.59-mm disks were removed from 18 leaf blades for an equivalent leaf tissue area. The absorbance at 664 and 647 nm was measured with a Hitachi U-2000 spectrophotometer (Hitachi Instruments, Inc., Japan). Chlorophyll content ([micro]g [cm.sup.2]) was then determined by the Moran formula (1982).

Leaf widths were determined by removing 2.5 cm from the middle of the newest most fully expanded leaf blades of 10 random plants in each subplot with a razor blade. Cut leaf samples were immediately placing in water to prevent will. These samples were then blotted dry and the average leaf area determined with a Li-Cor model 3100 leaf area meter (LI-COR, Lincoln, NE).

The number of tillers per plant was determined from an 81 [cm.sup.2] (10.2-cm diam) round plug from a randomly determined location within each subplot. A single mother plant with no daughter plants was determined to have zero tillers.

A hole drill (Black and Decker, Towson, MD) was used to remove a 4.5 cm in diameter x 15-cm deep root plug to collect root samples. Roots were separated from the thatch layer and the sand/peat root zone mix. Roots were then oven dried at 105[degrees]C for 48 h in a VWR 1350 F drying oven (VWR Scientific, West Chester, PA) and weighed.

Chloroplast ultrastructure and leaf histology were analyzed by transmission electron microscopy (TEM) at the Molecular and Cellular Imaging Center (Ohio Agricultural Research and Development Center, Wooster, OH). Plant tissue was infiltrated and fixed in 3% (v/v) glutaraldehyde, 1% (v/v) paraformaldehyde, in 0.1 M potassium phosphate buffer (pH 7.4) for 4 h at room temperature. Samples were washed three times with 0.1% (w/v) potassium phosphate buffer (pH 7.4), post-fixed in 2% (w/v) Os[O.sub.4] in 0.1 M potassium phosphate buffer (pH 7.4) for 30 min at room temperature, washed three times with distilled water, and dehydrated in a graded ethanol-acetone series. Samples were then embedded in Spurr's resin following manufacturer instructions (Electron Microscopy Sciences, PA). Ultra-thin sections were counterstained with 3% uranyl acetate in 50% ethanol for 35 min, and 2% aqueous bismuth sulfate stain for 15 min. Samples were then viewed on a Hitachi H-7500 transmission electron microscope. Samples were viewed at 150 and 300X magnification for measurement of mesophyll thickness and air space, epidermal cell structure and size, and chloroplast orientation while 4000x was used for viewing chloroplast ultrastructure. SigmaScan scientific software (SPSS Science, Chicago, IL) was used to measure various components of chloroplast ultrastructure and leaf histology from three to five 19- x 24-cm micrograph images per cultivar and light treatment combination.

The data were analyzed as three randomized complete block studies combined over locations (light environments), by the analysis of variance procedure of SAS (SAS Institute, 1990). Data are presented as means with standard deviations. Orthagonal contrasts were used to hypotheses of the different light environments.

RESULTS

The various light treatments affected tiller production in both years of the study (Table 2). Plants of both cultivars grown in FS had significantly greater tillering rates than those grown in either shade treatment. No tillering was observed in either cultivar under DS in the first year. The shade tolerant cultivar Plantation had higher tillering rates than Equinox. Plantation tiller production was two times that of Equinox in FS, but there were no differences between the two cultivars in either shade environment (Table 2).

In Year 2, tiller production differed in plots with different PPF and R:FR ratio (Table 3). Tillering increased on all plots from the first to the second year of the study, with the greatest rate of increase observed under the two shade treatments. As in Year 1, FS plants had more tillers than any other treatment, producing 1.5 times more tillers than NS and 3.5 times more than DS. Although both cultivars tillered less in shade than in FS, exposure to DS resulted in significantly less tillering than exposure to NS.

Leaf morphology differed between PPF and R:FR treatments in Year 1 (Table 2). Plants grown in FS developed significantly wider leaf blades than those in shade. Plants grown in high R:FR ratio shade had greater leaf widths than those grown in low R:FR ratio shade (Table 3). Average leaf widths between cultivars were not significantly different. However, differences were observed Year 2, as greater leaf widths occurred in grasses grown under high R:FR ratios than low R:FR ratios (Table 3), As in Year 1, leaf widths of FS plants exceeded those of plants in both shade treatments. Also, leaf widths of NS plants again exceeded DS plants in shade.

Accumulation of dry matter in the roots was influenced by reducing PPF. However, R:FR ratios had no effect (Table 3). On average, FS plants had about five times more root mass than plants grown in either NS or DS. In shade, changes in spectral composition did not result in changes in root mass. There were no differences in root mass between the two cultivars in any treatment.

In Year 1, NS plants contained slightly higher amounts of chlorophyll than DS plants (Table 2). However, in Year 2, even greater differences were observed between the light treatments as FS and NS promoted overall higher chlorophyll contents than DS (Table 3). In shade, high R:FR ratios in NS led to higher chlorophyll contents than low R:FR ratios of DS. Again, Plantation and Equinox chlorophyll contents did not differ in Year 2.

Leaf thickness varied among the three treatments, but not between cultivars (Fig. 1, Fig. 2). PPF had the greatest influence on leaf thickness. FS produced considerably thicker leaf blades than those grown in either shade treatment. However, in low PPF, NS plants had significantly thicker leaves than DS plants (Table 4).

[FIGURES 1-2 OMITTED]

Epidermal thickness of grass leaves was influenced by the light treatments and contributed to increased thickness of sun leaves versus shade leaves (Table 4). There were differences in epidermal thickness due to PPF, as leaves exposed to high PPF had thicker epidermal cell layers than those grown in either shade treatment. The epidermis of NS leaves was significantly thicker than that of DS leaves. Cultivars did not differ with respect to epidermal thickness in any of the treatments.

In all treatments and cultivars, the proportion of mesophyll contributing to differences in leaf thickness did not change (Table 4). Mesophyll occupied approximately 85% of the cross-sectional area of the leaf whereas epidermis occupied roughly 15%, regardless of light treatment or cultivar (Fig. 3, Fig. 4).

[FIGURES 3-4 OMITTED]

Fraction of air space relative to overall leaf thickness was more than two times greater in plants grown under low PPF than high PPF (Table 4, Fig. 3). In shade, percentage of air space in mesophyll tissues was unaffected by R:FR ratio under low PPF. Additionally, percent age of air space between cultivars was similar under all light treatments.

Neither chloroplast dimensions nor the number of grana per chloroplast were influenced by PPF or R:FR ratio (Table 5). Grana thickness was influenced by PPF (Table 5). Chloroplasts from plants grown under FS had thicker grana stacks than those grown in either shade environment. No other differences were seen with regard to the influence of light treatments on grana thickness.

DISCUSSION

Many morphological changes seen under low PPF are further influenced by R:FR. Less root production was found under decreased PPF, regardless of R:FR, in agreement with previous studies (Lee et al., 1996). The reduction of R:FR primarily results in decreased tillering. At the cellular level, more air space and less grana thickness were found in tall rescue plants under reduced PPF. Tillering, leaf width, chorophyll content, and leaf thickness were affected by changes in both PPF and R:FR.

In both years, light intensity was the most influential factor controlling tiller production. However, in the shade, high R:FR ratios enhanced tiller production. In the initial 3 mo of the study, tillering occurred in NS (high R:FR), but none was observed in DS (low R:FR). Because plots were established in June, nearly 6 wk following tree leaf development, DS plots were exposed to low R:FR ratios for the entire period from germination (June) to Year 1 sampling (September). A noticeable increase in tillering occurred from Year 1 to Year 2 in all treatments, especially in DS (Table 3). This is probably because grass plants must reach a minimum level of maturity before tillering is possible (Beard, 1973). There is a strong correlation between leaf thickness and photosynthetic capacity (Oguchi et al., 2003). Therefore, it is possible that there is a relationship between the increase in leaf thickness observed in the NS compared to DS and tiller production.

A relationship between PPF and chlorophyll content was not observed in Year 1 of this study (Table 2). However, the effects of increased R:FR ratios in this study were reflected in the higher chlorophyll contents of plants in NS relative to plants in DS (Table 2, 3). Transferring plants of many species to far-red-attenuated light results in greater chlorophyll per unit area (McMahon and Kelly, 1995: Rajapakse et al., 1999). Buisson and Lee (1993) report that papaya (Carica papaya L.) leaves grown under high R:FR ratios had greater chlorophyll contents ([micro]g chlorophyll [cm.sup.-2]) than those grown in low R:FR ratios (FR-filtered shade) at similar levels of PPF. This supports the role of phytochrome in initiating increased chlorophyll production despite the low PPF in NS. In Year 2, the relationship between PPF and chlorophyll per unit area was difficult to interpret (Table 3). However, as in Year 1, chlorophyll content was higher in the NS plants. Because shaded turf generally has thinner leaves than leaves in full sun, results may have differed had chlorophyll been measured on a weight or volume basis. Leaves grown at low light intensities have more chlorophyll per unit weight or unit volume of leaf, but the chlorophyll content per unit area of leaf surface is often lower than leaves grown at higher light intensities due to differences in leaf morphology (Boardman, 1977).

Turfgrass plants in NS had the highest chlorophyll contents in both years. High R:FR ratios presumably promoted greater chlorophyll production by influencing phytochrome equilibrium. High light intensities have been shown to promote breakdown of chlorophyll through pigment photooxidation (Demmig-Adams and Adams, 1996; Beard, 1973). Therefore high light intensities may have contributed to a degradation of chlorophyll contents in full sunlight, whereas low light intensities likely prevented breakdown of chlorophyll.

The two cultivars did not differ in many of the measurements made despite the difference in relative shade tolerance of the cultivars. This may have occurred because we are comparing cultivars of similar and relatively shade-tolerant turfgrass species. However, the differing shade tolerances of the two cultivars could be seen in the chlorophyll production by each cultivar in response to changes in R:FR ratios in shade. Chlorophyll production by the shade-tolerant Plantation decreased by 24% in NS compared to DS. However, chlorophyll production by the shade-intolerant Equinox was 56% less under DS compared with NS. This would appear to be a significant factor contributing to the increased shade tolerance reported for Plantation relative to Equinox, since shade-intolerant taxa respond most strongly to reduced R:FR ratio (Lee et al., 1996).

Only minor differences in chloroplast development were observed in this study. The number of grana per chloroplast remained consistent throughout the treatments for Plantation but not Equinox. A significant increase in the number of grana from FS to shade in Equinox is a response expected of less shade tolerant plants. This is in contrast to the more shade-tolerant Plantation, which did show a change in grana number between FS and shade. Similarly, Wilkinson and Beard (1975) observed that relatively shade intolerant Kentucky bluegrass ultrastructure was altered by shade, whereas that of relatively shade tolerant fine rescue was not.

Grana thickness was greater in FS than either shade treatment. FS plants had planar, more uniform orientation of grana stacks whereas chloroplasts of plants grown in shade were more spread out across the chloroplast and appeared less organized. Staggered, interconnected organization of chloroplasts is thought to be an adaptation by plants in shade for maximizing light absorption under low PPF (Boardman, 1977).

In general, the response by chloroplast ultrastructure to shading and R:FR was minimal. Wilkinson and Beard (1975) found that shade tolerant 'Pennlawn' red fescue chloroplast ultrastructure to be similar under various PPF. This response is therefore characteristic of a species having good shade tolerance. However, the shade intolerant Kentucky bluegrass exhibited different chloroplast ultrastructure depending on the level of PPF. Results from our experiment imply differences in chloroplast ultrastructure at varying PPF levels may not exist between cultivars within a shade tolerant species.

In summary, our results suggest that while turfgrass photomorphogenesis in shade is influenced by changes in PPF, many characters are further influenced by changes in the R:FR ratio. Under low PPF, high R:FR ratios led to increased tillering, leaf blade width and thickness, and chlorophyll contents. However, other characters such as root mass do not appear to be influenced by light quality and would be influenced any time PPF is reduced, regardless of R:FR.
Table 1. Average daily photosynthetic photon flux and red:far-red
ratio of the three light treatments. Photosynthetic photon
flux (PPF) season total is based on continuous measurements
taken from 14 June 2003 through 14 Oct. 2002. Red:Far-red
(R:FR) values are averages of measurements taken in June
and September of both seasons. R:FR is the ratio of the photon
flux ratio of light in the 10 nm band around 660 nm to light
around 730 nm. PPF was measured every 15 min and the
cumulative data stored using a Spectrum Technology data logger
and average daily total PPF (mol [m.sup.-2] [d.sup.-1]) was determined
using Specware software (Spectrum Technologies).

                          Average       Percent
Treatment                daily PPF       of FS            R:FR

                       mol [m.sup.-2]
                         [d.sup.-1]

Full sun (FS)               45.0          100     1.165 [+ or -] 0.026
Neutral shade (NS)           3.2            7     1.021 [+ or -] 0.067
Deciduous shade (DS)         3.8            8     0.428 [+ or -] 0.065

Table 2. Comparison of full sun, neutral shade, and deciduous
shade treatments on 'Plantation' and 'Equinox' tall fescue
cultivars for 2001. Measurements are treatment means [+ or -] standard
deviation that were obtained September 2001 from a 10.2-cm
diam soil core for tiller counts or a 4.5-m round by 15-cm
deep soil core, removing thatch, 75 d after seeding.

                                                     Leaf
                               Tillers              width

Treatments-cultivars         [cm.sup.-2]              mm

Full sunlight
  Equinox                 0.36 [+ or -] 0.05   1.5 [+ or -] 0.2
  Plantation              0.99 [+ or -] 0.44   2.0 [+ or -] 0.8
Neutral shade
  Equinox                 0.15 [+ or -] 0.02   1.5 [+ or -] 0.2
  Plantation              0.19 [+ or -] 0.06   1.6 [+ or -] 0.3
Deciduous shade
  Equinox                         0            0.9 [+ or -] 0.2
  Plantation                      0            1.0 [+ or -] 0.2
Analysis of variance
Source                          P > F               P > F

Light                           <0.01                0.04
  Sun vs. shade                 <0.01                0.05
  Neutral vs. deciduous            NS                0.05
Replication (light)                NS                  NS
Cultivar                         0.04                  NS
Light x cultivar                 0.04                  NS

                              Chlorophyll
                                content

Treatments-cultivars      [micro]g [cm.sup.-2]

Full sunlight
  Equinox                 41.4 [+ or -] 7.40
  Plantation              46.7 [+ or -] 4.08
Neutral shade
  Equinox                 49.4 [+ or -] 9.48
  Plantation              51.6 [+ or -] 4.17
Deciduous shade
  Equinox                 44.6 [+ or -] 6.19
  Plantation              39.2 [+ or -] 4.38
Analysis of variance
Source                           P > F

Light                        NS ([dagger])
  Sun vs. shade                     NS
  Neutral vs. deciduous           0.05
Replication (light)                 NS
Cultivar                            NS
Light x cultivar                    NS

([dagger]) NS = Nonsignificant at P = 0.05.

Table 3. Comparison of full sun, neutral shade, and deciduous
shade treatments on 'Plantation' and 'Equinox' tall fescue
cultivars for 2002. Data based on micrographs of three leaf
cross-sections per treatment. Treatment means [+ or -] standard
deviation were obtained September 2002 using SigmaScan image
analysis software.

                                                     Leaf
                               Tillers              width

Treatments-cultivars         [cm.sup.-2]              mm

Full sunlight
  Equinox                 1.06 [+ or -] 0.14   3.2 [+ or -] 0.2
  Plantation              1.09 [+ or -] 0.11   2.9 [+ or -] 0.1
Neutral shade
  Equinox                 0.75 [+ or -] 0.12   3.5 [+ or -] 0.2
  Plantation              0.62 [+ or -] 0.14   3.1 [+ or -] 0.1
Deciduous shade
  Equinox                 0.25 [+ or -] 0.12   1.6 [+ or -] 0.1
  Plantation              0.32 [+ or -] 0.05   1.5 [+ or -] 0.4
Analysis of variance
Source                          P > F               P > F

Light                           <0.01               <0.01
  Sun vs. shade                 <0.01                0.01
  Neutral vs. deciduous         <0.01               <0.01
Replication (light)                NS                  NS
Cultivar                           NS               <0.01
Light x cultivar                   NS                  NS

                                 Root              Chlorophyll
                                 mass                content

Treatments-cultivars              g            [micro]g [cm.sup.-2]

Full sunlight
  Equinox                 3.11 [+ or -] 0.87   35.5 [+ or -] 2.01
  Plantation              3.27 [+ or -] 0.19   34.3 [+ or -] 2.48
Neutral shade
  Equinox                 0.33 [+ or -] 0.09   53.8 [+ or -] 4.33
  Plantation              0.58 [+ or -] 0.09   50.1 [+ or -] 3.38
Deciduous shade
  Equinox                 0.69 [+ or -] 0.10   23.5 [+ or -] 7.09
  Plantation              0.90 [+ or -] 0.41   37.9 [+ or -] 2.80
Analysis of variance
Source                          P > F                 P > F

Light                           <0.01                 <0.01
  Sun vs. shade                 <0.01                  0.01
  Neutral vs. deciduous     NS ([dagger])             <0.01
Replication (light)                NS                    NS
Cultivar                           NS                    NS
Light x cultivar                   NS                  0.04

([dagger]) NS = Nonsigniticant at P = 0.05.

Table 4. Proportion of leaf tissues relative to total leaf
thickness. Data is based on measurements of micrographs of
three leaf cross-sections per treatment. Micrographs were
taken at 150 x magnification with a transmission electron
microscope. Data based on micrographs of three leaf
cross-sections per treatment. Treatment means [+ or -]
standard deviation were obtained September 2002 using
SigmaScan image analysis software.

                                Leaf
                              thickness           Mesophyll

Treatments-cultivars          [micro]m                %

Full sunlight
  Equinox                 190 [+ or -] 9.1    85.7 [+ or -] 1.1
  Plantation              194 [+ or -] 19.3   86.5 [+ or -] 0.5
Neutral shade
  Equinox                 164 [+ or -] 12.4   84.8 [+ or -] 1.0
  Plantation              154 [+ or -] 18.0   86.6 [+ or -] 0.7
Deciduous shade
  Equinox                 119 [+ or -] 17.7   84.6 [+ or -] 2.6
  Plantation              123 [+ or -] 13.1   84.1 [+ or -] 0.7
Analysis of variance
Source                          P > F               P > F

Light                           <0.01           NS ([dagger])
  Sun vs. shade                 <0.01                NS
  Neutral vs. deciduous          0.01                NS
Replication (light)              NS                  NS
Cultivar                         NS                  NS
Light x cultivar                 NS                  NS

                              Epidermis           Airspace

Treatments-cultivars                        %

Full sunlight
  Equinox                 14.3 [+ or -] 1.1   4.4 [+ or -] 0.9
  Plantation              13.4 [+ or -] 0.5   5.0 [+ or -] 1.0
Neutral shade
  Equinox                 15.2 [+ or -] 0.9   13.5 [+ or -] 1.5
  Plantation              13.4 [+ or -] 0.7   10.9 [+ or -] 0.6
Deciduous shade
  Equinox                 15.4 [+ or -] 2.6   12.6 [+ or -] 1.4
  Plantation              16.4 [+ or -] 1.7   11.0 [+ or -] 2.1
Analysis of variance
Source                          P > F               P > F

Light                            NS                 <0.01
  Sun vs. shade                  NS                 <0.01
  Neutral vs. deciduous          NS                  NS
Replication (light)              NS                  NS
Cultivar                         NS                  NS
Light x cultivar                 NS                  NS

([dagger]) NS = Nonsignificant at P = 0.05.

Table 5. Comparison of full sun, neutral shade, and deciduous shade
treatments on chloroplast ultrastucture of 'Plantation' and 'Equinox'
tall fescue cultivars. Chloroplast and grana measurements were obtained
from scans of micrograph images of mesophyll cells taken at 4000x
magnification with transmission electron microscope (45 chloroplasts
per treatment). SigmaScan image analysis software was used to make
manual measurements. Measurements are treatment means [+ or -]
standard deviation that were obtained September 2002 from five
random plants from a 4.5-cm round by 15-cm deep soil core.

                                   Chloroplast axis length

                                 Long                Short

Treatment-cultivars                      [micro]m

Full sunlight
  Equinox                 5.04 [+ or -] 0.49   2.91 [+ or -] 0.49
  Plantation              5.09 [+ or -] 0.27   3.49 [+ or -] 0.48
Neutral shade
  Equinox                 4.98 [+ or -] 0.22   2.80 [+ or -] 0.27
  Plantation              5.50 [+ or -] 0.15   2.66 [+ or -] 0.26
Deciduous shade
  Equinox                 5.57 [+ or -] 0.04   2.91 [+ or -] 0.46
  Plantation              5.23 [+ or -] 0.30   3.57 [+ or -] 0.14
Analysis of variance
Source                          P > F                P > F

Light                       NS ([dagger])              NS
  Sun vs. shade                   NS                   NS
  Neutral vs. deciduous           NS                   NS
Replication (light)               NS                   NS
Cultivar                          NS                   NS
Light x cultivar                  NS                   NS

                                  Grana
                           [chloroplast.sup.-1]     Grana thickness

Treatment-cultivars                                     [micro]m

Full sunlight
  Equinox                 10.82 [+ or -] 2.35      0.31 [+ or -] 0.02
  Plantation              21.62 [+ or -] 4.15      0.31 [+ or -] 0.05
Neutral shade
  Equinox                 19.22 [+ or -] 4.83      0.24 [+ or -] 0.04
  Plantation              18.11 [+ or -] 1.23      0.25 [+ or -] 0.02
Deciduous shade
  Equinox                 21.51 [+ or -] 1.88      0.22 [+ or -] 0.03
  Plantation              21.74 [+ or -] 4.39      0.24 [+ or -] 0.03
Analysis of variance
Source                            P > F                  P > F

Light                               NS                   <0.01
  Sun vs. shade                     NS                   <0.01
  Neutral vs. deciduous             NS                     NS
Replication (light)                 NS                     NS
Cultivar                            NS                     NS
Light x cultivar                   0.05                    NS

([dagger]) NS = Nonsignilicant at P = 0.05.


Abbreviations: DS, deciduous shade; FS, full sunlight; NS, neutral shade; PPF, photosynthetic photon flux; R:FR, Red:far-red.

ACKNOWLEDGMENTS

The authors wish to thank Karli Fitzelle and Tea Meulia at the Ohio Agricultural Research and Development Center Transmission Electron Microscopy Laboratory at Wooster, Ohio for their assistance.

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B. G. Wherley, D. S. Gardner, * and J. D. Metzger

B.G. Wherley, Dep. of Crop Science, Campus Box 7620, North Carolina State Univ., Raleigh, NC 27695: D.S. Gardner and J.D. Metzger, Dep. of Horticultural and Crop Science, 2021 Coffey Road, The Ohio State Univ., Columbus, OH 43210-1086. Salaries and research support provided in part by State and Federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. Journal Article Number HCS03-36. Received 22 Apr. 2004. Turfgrass Science. * Corresponding author (gardner.254@osu. edu).
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Title Annotation:Turfgrass Science
Author:Wherley, B.G.; Gardner, D.S.; Metzger, J.D.
Publication:Crop Science
Geographic Code:1USA
Date:Mar 1, 2005
Words:5520
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