Crown Buds Research Articles

Reactivation of vessel expansion in relation to budbreak in sycamore (Acerpseudoplatanus) trees

The origin and progress of production of the first vessels of the new growth ring has been followed within trees of sycamore (Acerpseudoplatanus L.) and compared with stages of bud and shoot development within the crown and with variation in temperature at bud level. Reactivation of vessel expansion originated at the bud base when the bud had elongated 50% over dormant length; this stage of budbreak was delayed by 2 days for each metre up the crown. Vessel expansion did not appear to progress actively down branches until the leaf tips began to emerge. Changes in carbon partitioning may suggest that this lag period is associated with the importing phase of bud growth, progress beginning when the leaves become self-sufficient in assimilates. After the lag period, progress of vessel expansion down the branches was estimated to be about 3 cm day−1. Expanding vessels reached the trunk first in upper or middle crown, while the predetermined leaves of the lower and middle crown buds were expanding. Vessel expansion progressed more rapidly down the trunk than down branches; the predetermined leaves of the lower to middle crown had fully expanded by the time vessel expansion reached the base of the trunk.

The Influence of Glyphosate on Bud Dormancy in Leafy Spurge (Euphorbia esula)

Glyphosate [N-(phosphonomethyl)glycine] was applied in the spring and fall to leafy spurge (Euphorbia esulaL. # EPHES) in the field at rates of 0.14 to 4.48 kg ai/ha. Fall applications of glyphosate at rates of 0.56 to 4.48 kg/ha stimulated axillary branching and caused an increase in the number of stems/m2by the end of the following summer in a dense population. This was a result of shoot growth from buds on the crown region of the root system. The absorption and translocation of14C-glyphosate applied to leaves of mature leafy spurge plants were evaluated at prebloom, full-bloom, and senescence phenological stages. Approximately 81% of the14C-glyphosate applied to the leaves of senescing plants was absorbed. There was a decrease in the proportion of14C translocated out of the treated leaf when applications were made after full bloom. Translocation of14C to the treated stem, nontreated stems, root crown, and roots did not differ with phenological stage in 1983. Translocation and concentration of14C in most plant parts in 1985 differed with phenological stage. Translocation to the crown buds as a percentage of the14C absorbed was highest at the senescence stage. At senescence and before soil freezing, leafy spurge crown buds demonstrate transient but active elongation toward the soil surface. This active development may account for the enhanced translocation of14C into the crown buds.

Regrowth of Quackgrass (Agropyron repens) Following Postemergence Applications of Haloxyfop and Sethoxydim

Previous research has shown that haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} and sethoxydim {2-[1-(ethoxyimino)butyl-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} give less control of quackgrass [Agropyron repens(L.) Beauv. # AGRRE] when applied at the five- to seven-leaf stage compared to the three- to four-leaf stage. Current research indicates that reduced control of quackgrass in the eight-leaf stage, compared to the four-leaf stage, was not due to reduced herbicide retention on leaves or to changes in residual herbicide activity in the soil following postemergence applications. The efficacy of both herbicides on rhizome bud kill did not change between the four- and eight-leaf stages following application to the foliage. However, the efficacy of both herbicides on crown tissue bud viability was less at the eight-leaf stage. Rhizome sink intensity (the capacity to accumulate radiolabel) was similar at both stages of development following14C-haloxyfop and14C-sethoxydim application to either upper or lower leaves. Crown tissue sink intensity was significantly less at the eight-leaf stage compared to the four-leaf stage following14C-sethoxydim application to either upper or lower leaves and following14C-haloxyfop application to lower leaves. These data suggest that crown bud regrowth contributes substantially to reduced control of quackgrass in advanced stages of growth following applications of haloxyfop and sethoxydim.

Photosynthate and Dry Matter Distribution in Effectively and Ineffectively Nodulated Alfalfa1

Ineffectively nodulated alfalfa (Medicago sativa L.) grown with combined N [In(+N)] was compared with symbiotically‐grown, effectively‐nodulated alfalfa (Sar) to determine whether ineffective nodulation had correlated effects on photosynthate partitioning into dry matter. Ineffectively nodulated alfalfa grown with [In( + N)] and without [In( − N)] combined N were compared to determine the effects of N stress on photosynthate partitioning. Either the topmost or lowest fully‐expanded, intact green leaf on the main stem was labeled with 14CO2 in pulse‐chase experiments. After a 24 h chase period, the plants were divided into source leaf, main stem, unexpanded leaves and shoot apex on the main stem, other fully‐expanded leaves on the main stem, shoots growing from axillary buds on the main stem, shoots growing from crown buds, crown, nodules, and root. The 14C partitioning was measured as relative specific activity (RSA) and percent of total plant recovered radioactivity (%TPR). The dry mass, %TPR, and RSA of aerial organs were similar in In( + N) and Sar. However, the dry mass and %TPR of the belowground organs (roots + crown + nodules) were 46% and 25% less, respectively, in In(+N) than in Sar. This differential partitioning of dry matter and photosynthate to roots and crowns between the populations indicates that the single recessive gene for ineffective nodulation may have correlated effects on growth or development. The allocation of photosynthate from the topmost and lowest fully‐expanded leaf was significantly (P<0.05) different to all organs except nodules and roots. The topmost fullyexpanded leaf was the primary supplier of photosynthate to the unexpanded leaves and shoot apex on the main stem, the main stem, and fully‐expanded leaves on the main stem. The lowest fully‐expanded leaf was the primary supplier to the shoots growing from axillary buds on the main stem, the shoots growing from crown buds, and the crown. The dry mass, RSA, and %TPR of the main stem, shoots growing from axillary buds on the main stem, fully‐expanded leaves on the main stem, and shoots growing from the crown were less in the In(−N) than in the In(+N). The converse was true for the unexpanded leaves and shoot apex on the main stem, crown, roots, and nodules. The carbon exchange rate of the topmost fully‐expanded leaf was reduced 45%, but the export of photosynthate significantly increased, under N stress. The dry mass, %TPR, and RSA of the nodules were greater by 19‐, 36‐, and 6‐fold, respectively, in In(−N) than in In( + N). These results indicate that the nitrate inhibition of nodulation and photosynthate partitioning to alfalfa nodules is unrelated to rhizobial effectiveness or to the functioning of the bacteroids.

Long-day Flower Initiation by Chrysanthemum

Abstract Thirty-eight cultivars of Chrysanthemum × morifolium Ramat. commonly grown in year-round flower production programs were grown continuously in long days. After 19 weeks of growth, 2 apparently were still vegetative, whereas 36 had formed flower buds; these failed to develop to anthesis and formed “crown buds”. The average number of leaves produced before the terminal flower bud (“long-day leaf number,” LDLN) ranged from 18.8 for ‘Bright Golden Anne’ to 78.2 for ‘Dignity.’ LDLN indicates whether a cultivar will form flower buds relatively early while growing in long days, and it identifies cultivars that need special attention during cutting production. It also could be used to control flowering in “timed-pinch” programs, and to characterize cultivars for breeding programs.

Establishment and multiplication of red clover plants by in vitro shoot tip culture

A procedure is described for the routine establishment and multiplication of red clover, Trifolium pratense L., shoot tips which should be applicable to a wide genotypic background. The addition of CO2 to the culture vial or use of polypropylene closures enhanced shoot multiplication at high levels of benzyladenine (BA). Horizontal orientation of crown buds resulted in more efficient multiplication. Culture of nodes from flowering stems was unsuccessful. The cytokinin BA was most effective for shoot multiplication at 2.0 mg/l with maximum shoot production by four weeks. A comparison of several genotypic sources revealed a 10-fold range in response to the multiplication medium with no differences observed among agronomic type or ploidy level. An additional study revealed that multiplication ability of a genotype can be determined after the second subculture since multiplication ability does not change during repeated subculture.

Peronospora trifoliorum . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Peronospora trifoliorum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Medicago sativa subsp. saliva, M. sativa subsp. falcata . DISEASE: Downy mildew of lucerne (alfalfa). Infected leaflets, which tend to be near the top of the stem, are light green or yellow. The affected areas can vary from small localized spots to larger areas of infected leaf or a systemic infection where the entire shoot may become yellow, stunted and swollen. GEOGRAPHICAL DISTRIBUTION: Worldwide, wherever lucerne is grown. CMI Map No. 343 includes records on clover and other hosts. TRANSMISSION: Mycelium is reported to overwinter in the crown bud (42, 617). Conidia are produced the following spring and in damp and humid conditions soon spread the disease. Oospores occur but reports on their frequency under field conditions are so few that it is difficult to assess their importance in overwintering the disease. Seed transmission, though suspected by Eriksson (1930) and also reported from Italy in a sample of seed from Argentina (Campbell, 1922), is thought to be unimportant (Richardson, 1979).

Photoperiod and Continuous Irradiation Studies of Chrysanthemum with High-pressure Sodium Lamps

Abstract High-pressure sodium (HPS) lamps were as effective as incandescent (INC) lamps for controlling photoperiod with 10 cultivars of Chrysanthemum × morifolium Ramat. for up to 8 weeks when used at illuminances (108 to 215 lux) generally recommended. Two garden cultivars studied initiated flowering under long days (LD) with both lamps. In a second study, 11 chrysanthemum cultivars were grown under continuous irradiation from HPS lamps. Six cultivars were vegetative after 8 weeks; the other 5 cultivars developed crown buds or lost apical dominance.

Flexible Alfalfa Management: Early Spring Utilization1

Providing low‐cost high quality grazing for livestock early in the spring when pasture and hay are limited may increase body weights at economical prices. Current alfalfa (Medicago sativa L.) varieties may be suitable for such grazing if either stands or yields are not greatly reduced by early spring harvests. To evaluate the possibilities of early spring alfalfa grazing, two severities of cutting to simulate grazing were imposed at several spring dates by removing one‐half the leaf area index (LAI) and all the LAI by cutting to a 5‐cm stubble height. Spring utilization dates, based on accumulating 1, 2, 3, and 4 LAI units, occurred on about 9 April, 27 April, 6 May, and 25 May, respectively. During the remainder of the season, harvesting hay at onetenth bloom was considered lenient management for recovery. The 9 April grazing cut, leaving about onehalf the LAI, enhanced the first hay yields as compared with removing nearly all the leaf area. However, at 6 May with an LAI of about 3, leaving one half the leaf area, resulted in lower yields and decreased quality of the following hay harvest as compared with a grazing cut at 5 cm which removed all leaf area. Regrowth from tall stubble remaining after the 6 May grazing cut generally orginated from branches at axillary buds which had smaller stems than those growing from crown buds. Early spring grazing cuts delayed the first hay harvest. This delay is desirable since favorable hay‐making weather is more likely later in the season. Number of regrowth days to one tenth bloom decreased between April and mid‐June and increased thereafter. Regrowth after early August cuts did not flower due to short days of late summer.Total season yields were similar for all treatments. Residual yields in subsequent years showed no detrimental effects due to date or severity of spring grazing cuts. Utilization of alfalfa in early srping by grazing and taking the first hay harvest about 3 weeks later than normal appears to be a feasible alternative system for flexible alfalfa management.

ABA Content and Levels of GA-like Substances in Asparagus Buds and Roots in Relation to Bud Dormancy and Growth1

Abstract A high concentration of inhibitors which were as high as that of gibberellin (GA)-like substances was found in young asparagus (Asparagus officinalis L.) spears using the rice seedling bioassay, and one of inhibitors was identified as abscisic acid (ABA) by gas chromatography. Endogenous ABA was extracted more thoroughly from the lyophilized materials than from frozen tissue. ABA level was the highest in tops including growing points of spears, and was always higher in the distal half than in the proximal, and higher in the cortex than in the pith. Free ABA levels tended to increase with the development of spears, while bound ABA levels remained the same irrespective of age. Three peaks of ABA were found in crown buds and root tips in March or April, August and December. Presumably asparagus crowns were in the deepest dormancy around the middle of December. Clearly the degree of dormancy from October to January paralleled ABA levels in crown buds and root tips. Endogenous levels of ABA in buds at developing stages was found highest in the resting buds.

CHANGES IN THE COLD HARDINESS OF ALFALFA DURING FIVE CONSECUTIVE WINTERS AT BEAVERLODGE, ALBERTA

Plants of Medicago falcata ’Anik’ were samples to assess their relative cold hardiness during the fall, winter and spring periods from 1974–75 to 1978–79. Precipitation and soil temperature patterns and cold hardiness profiles varied considerably from year to year. Environmental conditions in the fall appeared to exert the greatest influence on the cold hardiness profile and the maximum cold hardiness level in mid-winter. In general, plants started to harden in mid-September, but during one fall hardening period there was a delay associated with the early development of crown buds and the accompanying flush of growth during August and September. During two fall hardening periods, water-saturated soil conditions were associated with a dehardening phase in October. Conditions favoring delayed fall hardening and complete dehardening in the late fall were also associated with a lower level of hardiness in mid-winter. The maximum hardiness level, and the month during which it occurred, fluctuated considerably each year. Plants began dehardening as soil temperatures increased in late winter and early spring during 3 of the 5 yr. In the remaining 2 yr, plants began to deharden prior to an increase in soil temperature.

Heat Stress as a Special Purpose Alternative to Clipping in Alfalfa1

AbstractRegrowth in alfalfa (Medicago sativa L.) usually is studied following cutting. The possibility that regrowth after a different type of defoliation might reveal useful information led to the present greenhouse and chamber study. By exposing plants for 5 or 6 hours to heat reaching 52 C, aerial tissues were killed but crown buds survived to regrow. The heat‐stressed plants were delayed from 7 to 14 days in attaining the shoot numbers of clipped plants, but this regrowth appeared morphologically normal and initially was not influenced by the living residual leaf or buds found on stems below a cutting height. Certain attributes of regrowth, following high temperature exposure may prove useful in future research. When plants 50 to 92 days of age received the same stress, the older plants produced shoots in regrowth more rapidly than did the younger. Within an age group, those plants in flower when stressed produced more shoots than did those not yet showing flower buds when stressed. Individual plants with larger shoot numbers before either clipping or heat stress produced more shoots during regrowth.

Role of Anthracnose in Stand Thinning of Alfalfa in Delaware1

AbstractAnthracnose, caused by Colletotrichum trifolii Bains, is widespread on alfalfa (Medicago sativa L.) in Delaware and thinning of alfalfa stands is believed to be at least partially due to anthracnose. The purpose of this field study was to determine the effect of C. trifolii on winter survival of alfalfa. Alfalfa plants growing on a Typic Haplueults soil, with and without symptoms of anthracnose, were tagged prior to winter dormancy to determine the effects of C. trifolii on winter survival. Other factors affecting winter survival of alfalfa were evaluated by removing another group of plants with and without anthracnose symptoms from the experimental site before winter dormancy. The following parameters were evaluated: root and crown rot, insect feeding on root and crown tissues, presence of new crown buds, root and crown tissue weights, and total nonstructural carbohydrate levels. Soil surrounding the roots of removed plants was analyzed for soil acidity, P, K, Ca, Mg, and B. Colletotrichum trifolii‐infected plants had 22 to 85% lower winter survival values when evaluated the following spring. Colletotrichum trifolii‐infected plants evaluated prior to winter dormancy had 7% smaller root systems and 29% fewer plants with new crown buds, but did not have significantly different levels of crown and root rot or root insect damage. Soil tests, indicated no relationship between soil parameters measured and anthracnose. It is concluded that anthracnose was the principal factor responsible for stand thinning of alfalfa during the winter dormant period.

Influence of Cutting Management and Environmental Variation on the Yield, Bud Activity, and Autumn Carbohydrate Reserve Levels of Crownvetch1

Abstract‘Chaining’ crownvetch (Coronilla varia L.) was grown at four West Virginia locations: Morgantown, Wardensville, Reedsville, and Point Pleasant. These locations vary in amount and distribution of rainfall, temperature, snow cover, and length of growing season and show how combinations of environmental factors affect yield, morphology, and carbohydrate reserves. Yield and bud activity as affected by cutting at different growth stages and heights are presented. The effect of two and three harvests per season on yield and fall carbohydrate levels was also studied.Yields varied greatly among locations and years. Greater than 10,000 kg/ha were produced at Morgantown in 1969 and Reedsville in 1970 compared with total yields at Point Pleasant of 2,000 to 4,000 kg/ha from a thin stand. Greater yields generally were produced by two rather than three harvests per season. Clipping to stubble heights of 7.5 or 15.0 cm resulted in similar yields. First cutting yields generally increased as the first harvest was delayed to full bloom (mid‐June); however, delaying harvest past this period seldom increased yield. Cutting treatments did not detrimentally affect any of the stands, except possibly at Morgantown, where general vigor of the stand was lower the second season.The proportion of axillary buds producing growth increased with delay of spring harvest until full bloom and then declined. Delay of the first cutting and adequate moisture increased the proportion of axillary buds that produced regrowth. Cutting at different stubble heights generally had no effect on activation of axillary buds.Initiation of growth from crown buds was determined 2 weeks after cutting. Active buds at the crown and up to 2.5 cm from the base of 100 randomly selected stems were counted. Growth initiation from crown buds was greater when plots were cut at 7.5 cm than when cut at 15.0 cm for most cutting dates and locations. Crown bud activity was generally less during early spring and periods of moisture stress.Total non‐structural carbohydrates (TNC) in autumn were similar among locations. Slightly higher TNC values were associated with the 15.0 cm cutting heights, due mainly to changes in starch levels.

Tillering, Nonstructural Carbohydrates, and Survival Relationships in Alfalfa1

We attempted to assess the relationships of nonstructural carbohydrates and tillering with survival and productivity by identifying alfalfa (Medicago sativa L.) clones that were tolerant and others that were intolerant of frequent harvests and then comparing their response patterns. Vegetatively propagated alfalfa was grown in the field and subjected to three cutting frequencies during its second year. In autumn of 1972 when the season of cutting was completed, the plants were classified as having low, intermediate, or high tolerance to frequent cutting on the basis of survival. Plants were harvested and their roots removed from the soil. They were classified as tillering if elongated crown buds were present, and as nontillering if no elongation of crown buds were evident.Root and crown dry weight and total nonstructural carbohydrates (TNC) content (g/plant) of the fall‐harvested plants decreased from low‐ to high‐cutting tolerance plants, but the reverse was true for TNC concentration. The patterns were the same for both tillering and nontillering plants, but in each classification, the values were 25 to 50% greater for tillering than for nontillering plants. The differences in root and crown dry weight were associated with differences in TNC content.After the field investigation, the same clones were grown in a greenhouse. Root and crown tissues of greenhouse‐cultured plants classified as frequent (those surviving frequent cutting) attained a high percent TNC soon after cutting. Clones that did not survive the frequent field cuttings (low and intermediate tolerance to frequent cutting) did not increase in crown TNC percentage in the greenhouse until flower development (or tiller initiation) had begun. Survival and production of alfalfa may be improved by selecting genotypes that produce new tillers early in the regrowth cycle.

TILLER GROWTH AND DEVELOPMENT CYCLE IN BROMUS INERMIS GROWN FOR SEED IN SOUTHERN MANITOBA

Tiller production and development by brome-grass (Bromus inermis Leyss.) grown on Red River clay and fertilized with 207 kg/ha of 27–14–0 in spring, midsummer or late fall were compared at frequent intervals. Seed yields in the range 225–750 kg/ha were obtained. Seed production in 1964 equalled the combined production of 1965 and 1966. Differences due to the addition of fertilizer were not evident until the third harvest year. Growth of the overwintering tillers commenced in April. Jointing started in early May, probably in response to suitable temperatures, and stopped in late August when daylength shortened to less than 15½ hours. During the jointing period, the rosette tiller was an evanescent stage between crown buds and jointed tillers. Shortly after jointing started, the number of crown buds reached a low level. Replacement buds developed during June and July. From early August until growth cessation in late October, new tillers appeared continually from crown buds, and the rosette tiller stage represented a considerable proportion of the tiller population. Deterioration of the bromegrass stand to the "sodbound" condition was accompanied by reductions in tiller density and growth rate. Addition of fertilizer prevented or reduced this deterioration. The time of fertilizer application was not critical.

DEVELOPMENT OF THE INTERCALARY MERISTEM OF CYPERUS ALTERNIFOLIUS

The unique vegetative morphology of Cyperus alternifolius with its single elongated internode is ideal for developmental and experimental studies of internodal growth. The elongated internode is established by a primary rib meristem which extends from it to the third or fourth internode of the leaf crown. There is no internal histological differentiation of nodes. A secondary rib meristem, which is initiated later in the subapical region, produces the upper internodes of the leaf crown. Initiation of the secondary rib meristem and the start of extension of the elongated internode are correlated with the appearance of crown buds. The primary rib meristem is confined to a basal intercalary meristem (IM) at an early stage. The IM is mitotically active for many weeks and produces most of the internodal tissues. Quantitative data on percentage of cells dividing and cell length are presented for the IM at various stages of internodal development, Morphogenetic events are correlated with internodal growth. A histological gradient is described in the matured internode. Frequencies of stomates and papillae decrease and ground parenchyma cells shorten markedly toward the base. Epidermal cell length remains relatively constant but decreases in the region of the matured IM. Anatomical data are presented graphically and are correlated with internodal growth.

Effects of Temperature and Light Intensity on the Growth of Scrophularia Marilandica

The effects of temperature and light intensity on the growth of Scrophularia marilandica L. were studies under artificial, semi—natural, and natural environmental conditions. The plants in the controlled environment rooms were grown under 10 different combinations of temperature (48°/58°—63°/73°F) and light intensity (24—123 cal/cm2/day). The plants in the semi—natural experiment were grown outdoors on prepared plots representing seven levels of average radiation ranging from 20.4 to 405.7 cal/cm2/day. Net assimilation rate (NAR) was proportional to light intensity up to 123 cal/cm2/day in the growth rooms. In the semi—natural studies, it was proportional up to 150 cal/cm2/day and from this point up to 300 cal/cm2/day, NAR increased but not proportionally. Above 300 cal/cm2/day NAR was independent of solar radiation. Under controlled conditions NAR decreased slightly with age at the highest light levels. The length of the vegetative phase, the specific leaf area, and the leaf—area ratio were sharply decreased at higher light intensities. The dry weight of all plant organs was augmented by high light intensities. Roots and axillary shoots were especially sensitive. In the growth—room experiments, temperature effects were more pronounced than were light effects. Stem elongation was completely inhibited at temperature regimes below 63°/73°F, and leaf expansion was markedly diminished below 57°/68°F. Consequently the shoot developed a rosette habit and flowering was inhibited. Decreases in temperature to 48°/58°F had little effect of root growth. The net effect of low temperatures was to depress the shoot—root ratio. However, NAR was increased by a reduction in temperature from 63°/73° to 48°/58° at all intensities. The shoot—root ratio of shaded plants was increased to a greater extent by a rise in temperature than was that of the unshaded plants. Regardless of light level, plants at 48°/58°F consistently had a smaller shoot—root ratio than did those at 63°/73°F. Inhibition of stem elongation and subsequent rosette development at low temperatures were not affected by changes in light intensity. The usual development of greater leaf areas by plants growing under lower light intensities was partially reversed at low temperatures. In early spring shoots of native Scrophularia marilandica sprouted from crown buds attached to perennial roots. The timing differential between leaf expansion in April and shoot elongation in May appears to be a temperature—photoperiod interaction. In early spring and autumn cool temperatures which repressed shoot growth had little effect on root growth. Roots increased greatly in size through late summer into early autumn.

Transmission of Bacterial Wilt of Alfalfa By Ditylenchus Dipsaci (Kühn)

Corynebacterium insidiosum was transmitted by Ditylenchus dipsaci into alfalfa crown buds resulting in increased incidence of bacterial wilt in a wilt-susceptible variety.

Taproot Growth and Crown Bud Development in Biennial Sweetclover as Related to Photoperiod and Temperature1

Crop ScienceVolume 3, Issue 1 cropsci1963.0011183X000300010003x p. 4-7 Article Taproot Growth and Crown Bud Development in Biennial Sweetclover as Related to Photoperiod and Temperature1 M. J. Kasperbauer, M. J. KasperbauerSearch for more papers by this authorF. P. Gardner, F. P. GardnerSearch for more papers by this authorI. J. Johnson, I. J. Johnson Formerly Graduate Assistant (now Postdoctoral Resident Research Associate at Pioneering Research Laboratory for Plant Physiology, Beltsville), Professor of Agronomy, and former Professor-in-Charge of Farm Crops (now Research Director for Caladino Farm Seeds), Agronomy Department, Iowa State University.Search for more papers by this author M. J. Kasperbauer, M. J. KasperbauerSearch for more papers by this authorF. P. Gardner, F. P. GardnerSearch for more papers by this authorI. J. Johnson, I. J. Johnson Formerly Graduate Assistant (now Postdoctoral Resident Research Associate at Pioneering Research Laboratory for Plant Physiology, Beltsville), Professor of Agronomy, and former Professor-in-Charge of Farm Crops (now Research Director for Caladino Farm Seeds), Agronomy Department, Iowa State University.Search for more papers by this author First published: 01 January 1963 https://doi.org/10.2135/cropsci1963.0011183X000300010003xCitations: 7 1 Contributed from the Agronomy Department, Iowa State University. Journal Paper No. J-4356 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1321. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume3, Issue1January–February 1963Pages 4-7 RelatedInformation