B. Brooke

Cultivar and storage effects on germination and hard seed content of alfalfa

The impermeable coat of alfalfa (Medicago sativa L.) seed can reduce germination to an extent unacceptable for commercial use. The usual method of increasing germination of lots with high proportion of impermeable or hard seeds, mechanical scarification, can damage seeds. Experiments were conducted to determine the effect of cultivar, year of production and storage conditions on germination and hard seed content in alfalfa. Experiments with four Canadian cultivars indicated a significant effect of cultivar on seed weight, germination and hard seed content in freshly harvested seed. Year of production had a greater influence on these seed traits than cultivar. Under uncontrolled storage conditions, germination of 35 alfalfa synthetics increased and hard seed content decreased with time, although not at the same rate for all synthetics. Storage at 20 °C for up to 64 mo did not significantly decrease hard seed content. At 35 °C, hard seed content decreased continuously for all cultivars (for one cultivar to ...

Alfalfa seed germination tests and stand establishment: The role of hard (water impermeable) seed

Freeze thaw scarification has been observed to increase the germination rate of alfalfa (Medicago sativa L.) seed containing a large proportion of hard (water impermeable) seed in a 7-d laboratory germination test; however, a comparable increase in plant density is not always seen in the field. To investigate this discrepancy, a field experiment with untreated and scarified seed was carried out using cultivars with high (Apica, 35%; Barrier, 32%) and low (Apollo II, 1%; WL316, 0.3%) percentages of hard seed. Plants were counted at the three-trifoliate-leaf and 10% bloom stages in 1992, the planting year, and at 10% bloom in 1993. In the field, effects of scarification were seen only at the 10% bloom stage in 1992, increasing the plant densities of high hard seed cultivars by 17% while decreasing those of low hard seed cultivars by 10%. Two laboratory experiments were also done to determine the effect of temperature, lighting (light, shade, dark) and media (on blotter, in soil) on the germination of hard s...

Nonstructural Carbohydrate and Crude Protein in Pinegrass Storage Tissues

Nonstructural carbohydrates in storage tissues of pinegrass (Culumugrostis rubescens Buckl.) consist of sucrose, glucose, fructosan, and starch. The predominant polymer is a long-chain fructosan. An acid-extractable structural carbohydrate appeared to be xylan. Total nonstructural carbohydrates (TNC) of rhizome plus root tissue decreased during May, reached a minimum value during late May to early June, increased until late June, remained constant until late August, and then increased until November. The TNC level of crown tissue was low during May and early June and reached a peak during July and again in the fall. The crude protein concentration of rhizome plus root tissues was relatively constant throughout the season. Rhizome plus roots accumulated the largest amounts of TNC and crude protein. Stored organic compounds, such as carbohydrates, fats, and proteins, serve as food reserves for plants at times when photosynthesis cannot supply sufficient material for maintenance and growth (Trlica 1977, White 1973). These reserves must provide a source of energy and a source of molecules for growth when plants are completely defoliated; however, a definite role in regrowth of partially defoliated plants has not been proved (May 1960, Jameson 1964). In addition to a role for reserves in regrowth of completely defoliated plants, reserves are utilized by perennials during the winter (Menke and Trlica 1981). Root reserves typically decrease following harvest of aerial growth, and this decrease implies a role for reserves in regrowth. Whether or not reserves are used directly for regrowth, reserve level may serve as a measure of plant vigor following grazing (Trlica 1977). Grasses can be classified on the basis of the type of nonstructural carbohydrates (NC) that are accumulated: starch or fructosan accumulators (Smith 1968). Furthermore, they are classified according to the type of structural carbohydrate (SC); xylose is the predominant SC component in fructosan containinggrasses, while glucose is the predominant SC component in starch containing grasses (Ojima and lsawa 1968). Pinegrass (Calamagrostis rubescens Buck].) is an important source of forage on the forest ranges of British Columbia (McLean et al. 1969). Simulated grazing studies have established that pinegrass is most sensitive to herbage removal during July (Freyman 1970, Stout et al. l980), and that a pinegrass stand will deteriorate under simulated intensive grazing practices, such as clipping biweekly from May I5 to September I5 to a stubble height of 5 or IO cm (heavy and moderate grazing intensities respectively) (Stout et al. 1981). The objectives of this study were to determine: (I) type of carbohydrates stored: (2) seasonal pattern of carbohydrate and crude protein levels; and (3) morphological distribution of carbohydrate and protein reserves in pinegrass. D.G. Stout and B. Brooke are with Agriculture Canada. Research Station. 3015 Ord Road, Kamloops. B.C. V2B 8A9: M. Suzuki is with Agrictthure Canada. Rewarch Station. Charlottetown. Prince Edwards Island. CIA 7M8. Manuscrq received March 12. 1982. 440 Material and Methods Identification of the Carbohydrate Storage Form(s) in Pinegrass Pinegrass rhizomes were collected from the field in October and planted in 4-liter plastic pots containing loam, sand, and peat in the ratio of 1: l:l. Tiller growth and development occurred during a 3-month period in a growth chamber with a l6-hr photoperiod, a light energy of 90 Wme2 provided by fluorescent (Vita-Lite, DuroTest Corp., U.S.A.) and incandescent lamps, a day temperature of 20 f I C, and a night temperature of l8f I C. Tillers in I2 pots were then clipped to a 5-cm stubble height at 2-wk intervals during a 6-wk period. Tillers in 12 other pots received no clipping treatment during the 6-wk period. Following the 6-wk treatment period, 3 replicates of each treatment were harvested; each replicate consisted of 4 pots. A completely random design was used for this experiment. Plant material was harvested and divided into crown and rhizome plus root fractions. Crown tissue was defined as the I.5 cm portion of the tiller above its point of attachment to the rhizome. The crown sample included the growing point plus about 8 stem nodes, the attached scale leaves, and sheaths of at least 4 aerial leaves. The rhizome plus root fraction contained the rhizome and all of the attached fibrous root material that could be collected. Crown and rhizome plus root tissues were washed with cold water, freeze-dried, and ground to pass through a 40-mesh screen. Reducing sugars, total sugars, fructosans, starch, and H&04 extractable structural carbohydrates (SC) were then measured. To characterize the relative contribution of rhizomes and roots to the rhizome plus root tissue, on 2 dates the rhizome plus root tissue was separated into rhizome and fibrous root tissues following washing. Dry weight, TNC and crude protein were determined for each type of tissue. Similar chemical measurements were also made on crown tissue harvested from a native stand of pinegrass in May, June, and October, 1978. For this study, tissue samples from 2 of the 6 replicates of the seasonal trend study were used. Seasonal Trend of TNC and Crude Protein in Pinegrass Crowns and Rhizome Plus Roots In 1978, a 0.2-ha area of land immediately adjacent to the Poison Creek study site (Stout et al. 1980) was fenced to keep out cattle. Six 20 m2 plots were identified within the 0.2 ha area. Samples were collected on 20 dates from May 15, 1978, to October 23, 1979. Pinegrass sods (to a depth of IO cm in the mineral soil) were dug from a subplot (0.5 to 0.8 m*) within each 20 m2 plot. The subplots were harvested according to a completely random design. The bulk of the adhering soil was removed from the sods and the plant material was put into plastic bags and transported to the laboratory on ice. Sods were washed with cold water and crown and rhizome plus root samples were prepared as above, with the exception that drying was done in a forced air oven at 6oOC. TNC and crude protein content were then measured. Distribution of Dry Weight, TNC, and Protein in a Pinegrass Tiller On July 16, 1979, four areas (400 to 900 cm2) of pinegrass sods JOURNAL OF RANGE MANAGEMENT 36(4), July 1983

The effect of rainfall on Columbia milkvetch toxicity.

Highlight: Daily precipitation patterns were compared to the variation in miserotoxin concentration of Columbia milkvetch (timber milkvetch) sampled sequentially during the spring and summer of 1973 and 19 74. On rough fescue grasslands, the substantial increase in rainfall during the April-to-August period of 19 74 not only extended toxicity intervals but also increased miserotoxin levels during the prebud growth stage. A large-scale rain storm induced miserotoxin synthesis during the pod stage. Greater soil moistureholding capacity at one grassland experimental plot prevented a rapid decline in miserotoxin levels when drought conditions developed. In contrast, the toxicity trends on Douglasfir forest sites did not show a response to variations in precipitation and toxin differences between local sites were not significant. Consequently, a predictability equation was developed for Columbia milkvetch toxicity in Douglasfir forests on Gray Luvisolic soils.

Growth and development of pinegrass in interior British Columbia.

Pinegrass (Calumugrostis rubescens Buckl.) is an important source of forage on forested and clearcut ranges in interior British Columbia. The vegetative growth and development of this infrequently flowering grass was documented. This information is required to improve our understanding of pinegrass grazing resistance, and in turn, of its grazing management. Numbers of tillers me2 and number of leaves per tiller were counted at intervals during the growing seasons of 1978 and 1979. Leaf blade area was measured at intervals during 1978 and 1979. Tiller height was recorded during 1978,1979, and 1982, while shoot weight was recorded at intervals during 1982. Pinegrass had up to 4 leaves per tiller, but on average only 3.2 leaves were present by the time growth ceased in July. Total leaf blade area was reached in July, and is largely comprised of 2 leaves. Total leaf blade area(y) was predicted from tiller height (x): y = 0.39375+ 0.051604x + 0.00419223~2 (I?2 = 0.97). A large proportion of leaf blade area was dead by the end of July. Tiller weight reached a maximum in July; it increased during May to July owing to an increase in number of leaves, leaf area, and specific weight of leaves. Growth analysis indicated that net assimilation rate (NAR), and relative growth rate (RGR) were high in mid-May and then gradually decreased to zero in July. NAR and RGR of pinegrass appeared typical for C3 plants. Pinegrass (Calumugrostis rubescens Buckl.) provides 50% of the forage production within the interior Douglasfir (Pseudorsuga menziesii Mirb.) zone of British Columbia (McLean et al. 1969), and about 6 million hectares of this zone are used for summer grazing (Tisdale and McLean 1957). Single year simulated grazing studies have shown that pinegrass is most sensitive to herbage removal during July (Freyman 1970, Stout et al. 1980). A study involving successive years of simulated grazing showed that stand vigor, measured as number of tillers m-‘, decreased each year by an amount that depended upon the intensity of the herbage removal (Stout et al. 1981). Clipping biweekly during the summer growth period to a height of 5 cm caused the stand vigor to decrease by one-half after each year of clipping, whereas clipping biweekly during the summer growth period to a height of 10 cm caused the stand vigor to decrease by one-half only after 3.7 years. In British Columbia, pinegrass became unpalatable by mid-August (McLean 1967) and the quality of pinegrass was adequate for rapid growth of yearly steers or for maintaining weanling calves only until 1 August (McLean et al. 1969). This study was conducted to characterize the growth and development of pinegrass. Such basic knowledge will increase our understanding of the simulated grazing studies and the forage quality studies that have already been conducted. In addition, this knowledge will allow better design of future grazing studies, and can be used directly by range managers. Flowering culm production, location of growing point, and clump basal area are frequently used by range managers to document growth. Since pinegrass is a rhizomatous and infrequently flowering species, this study was limited to vegetative growth characteristics. Authors are research scientist and technican, Agriculture Canada, Range Research Station, 3015 Ord Road, Kamloops, B.C. V2B 8A9, Canada. Manuscript accepted September 27, 1984. 312 Materials and Methods The study was conducted during 1978, 1979, and 1982. The site was adjacent to the Poison Creek site described earlier (Stout et al. 1980), 18 km north of Kamloops airport at 1,189 m elevation. Limited weather data for this site and a nearby site (Pass Lake) have been published (McLean et al. 1969, Stout et al. 1980). The soil is a Gray Luvisol (A.L. van Ryswyk personal communication) (Canadian Soil Survey Committee 1978) on glacial till material, with a high percentage of parent rock fragments in the profile (Tisdale and McLean 1957). The forest cover was a moderately open stand of trembling aspen (Populus tremuloides Doug].), lodgepole pine (pinus contorta Dougl.) and douglasfir. The major shrubs were birch-leaved spirea (Spirea betulifoliu Pall.), rose (Rosa sp. L.), twinflower (Linnueu borealis L.), and creeping oregongrape (Berberis repens Lindl.). Pinegrass was the predominant graminoid and the major ground cover constituent. Forbs included broad-leaved lupine (Lupinus lutifofius Agardh), heart-leaf arnica (Arnicucordz~oliu Hook.), cream-flowered peavine (Larhyrusochroleucus Hook.) and wild strawberry (Fruguriu virginiunu Duchesne). In 1978,20 tillers within a 3 X6-m area were randomly selected. On each collection date, height above the forest floor of these 20 tillers was measured. Twenty tillers of similar height were then selected from within the 3 X 6-m area, harvested, placed in plastic bags containing a little water, and transported to the laboratory on ice for leaf area and weight measurements. In 1979 individual tillers were taken at l-m intervals from a different starting point on a permanent transect on each date. Each tiller selected was the first one intercepted by a meter stick laid at right angles to the line at the predetermined point. The height of a selected tiller was measured and then the selected tiller was harvested and transported to the laboratory as in 1978. In 1982 six collection points chosen visually to represent the site were staked. Based on visual observations, a representative group of tiller tufts was taken from within a 0.5-m radius. Twenty tillers were collected from each location on each date. All tillers in a tuft were taken before moving on to another tuft to get the total of 20 tillers. A tuft typically contained 6 tillers. The height of each tiller was recorded and then the tiller was harvested and transported to the laboratory. Leaf blade area, a measure of photosynthetic area, was measured in 1978 and 1979. At the laboratory, a tiller was removed from the plastic bag, number of leaves were counted, and the blades were immediately removed from the tiller and mounted on paper. Pinegrass has 4 or 5 small rudimentary leaves that were excluded from our measurements. The lowest 3 or 4 rudimentary leaves do not extend above the litter layer and they become dry brown scales as the tiller matures. The upper 1 or 2 rudimentary leaves extend above the litter and may turn green. Leaves were numbered, starting with the lowest on the stem (the oldest) having a blade length greater than 1 cm. Only the leaf blade area exerted from the sheath (of the preceding leaf) was measured. This included some immature leaves that were still rolled, so they were unrolled before being mounted. Leaves that were not at all exposed were discarded. In mounting, a 1.25 cm wide length of Magic (3M) transparent tape was laid on the working surface, adhesive side up, anchored at both ends. The pinegrass blade was placed on the tape, JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 abaxial side down, then flattened out so that its entire surface was in contact with the tape. The tape bearing the leaf was then affixed to a labelled sheet of paper. As soon as they were prepared, the pages of mounted leaves were photocopied since leaves were observed to shrink and curl on drying. Therefore, the photocopies were considered to be a more reliable record of leaf blade area. A dot planimeter (Bruning areagraph chart no. 4850) was used for leaf area determination. Means of duplicate counts for each of 3 planimeter placements on each blade were converted to square centimeters. Total and senesced blade areas were determined for each leaf blade. For blade weight determination, the mounted blades were peeled off the tape, dried 24 h in an 80°C oven, and weighed. This measurement was done on the whole (exerted) blade and so included both live and senesced tissues. Distribution of dry weight and percent dry matter within a tiller were determined in 1982. In the field the tiller was divided into 3 components. These were: “blade”, all completely exerted blades over 1 cm in length, and the exerted portion of immature blades; “sheath”, the foliage standing above the litter layer, excluding exerted blades and comprising sheaths, and blades 1 cm or less in length and all immature tissue enveloped in the sheaths;“subterranean tiller base”, the base of the tiller, lying beneath the surface of the litter layer, comprising (the vegetative) stem, rudimentary basal leaves and leaf sheaths of aerial leaves. The length of the tiller base ranged from I to 3 cm depending upon its point of origin on the previous year’s stem or on the rhizome, and on the depth of the litter layer. A bulk 20-tiller sample for each component was prepared for each of the 6 plots, weighed, oven-dried at 80’ C, and reweighed. Total tiller weight was calculated from the component weights. Growth analysis was done as described by Radford (1967). In 1978 and 1979, a relationship between leaf blade area and tiller height was established. In 1982, above ground level tiller dry weight (W) was related to growth time (t) by a second degree polynomial, W = a + bt + ct*. Leaf blade area (A) was estimated from tiller height and then related to growth time by a second degree polynomial, A q a’ + b’t + c’tz. April 31 was arbitrarily chosen as day 0 since observations over several years indicate that snow melt typically occurs during the period April 24 to May 7. Net assimilation rate (NAR) at a particular time was then estimated using NAR = l/A dW/dt and relative growth rate (RGR) at a particular time was estimated using RGR q I/W dW/dt. Leaf area ratio (LAR) is defined by LAR = RGR/NAR. Average NAR was calculated using NAR q [(Wz-Wl)/(Az-At)] [(In Az-ln Ar)/(tz-tt)], and average RGR was calculated using RGR = (In Wrln Wl)/(tz-tl). Each experiment reported here had a completely random design. Statistical analysis involved calculating_? f SE for a sample size of n. Curve fitting was done using a computer program th