Crop Physiology Course-Level And

Crop Physiology Course-Level And

AI crop physiologycourse--level and content F.~ P. Gardner and R. B. Pearce ABSTRACT amongcrops which tended to result in superficial treat- ment of basic concepts. (3) An introductory course Undergraduatecourses in crop science have crop science was offered at most institutions, but the traditionally beenpresented on a cropor crop-type content varied widely, ranging from essentially a begin- basis(grain, forage, oil, fiber, etc.) ratherthan on ning botany course to a general course in crop produc- conceptualbasis (crop physiology).Peer appraisal tion, often geographically oriented. Mitchell and of a coursein cropphysiology, proposed on a con- 3 ceptualbasis, wasobtained. Gardner suggested that key concepts in a body of In 1977, a questionnairewas sent to cropphysi. knowledge could be more effectively learned if subject ologists in the AmericanSociety of Agronomyfor matter was presented on a conceptual basis. Also, the their evaluation of the importanceof selected introductory course in crop science should contain the topics for a proposedcrop physiology course (1 broad, basic concepts. very important, to 5 = not important). Respond- Gardner (F. P. Gardner. 1971. A model for deriva- ents consideredthe proposedoutline logical. tion and organization of courses, p. 126. Agron. Abstr.) Sometopics were rankedas moreimportant than suggested that courses in crop science and soil science others for a crop physiologycourse. Major topics should embrace key concepts of these respective bodies suchas carbon(1.8), partitioning (1.8), plant of knowledge. The introductory course should consist stresses(1.9), photosynthesis(2o0), andlight (2.0) were viewedas moreimportant for the proposed of the families of concepts in the discipline as the basic coursethan respiration(2.1), growthand develop- units of instruction in the introductory course. An in- ment(2.1), harvestphysiology (2.1), mineralnutri- dividual family or group of related concepts, i.e., the tion (2.2), future challenges(2.3), andgrowth physical properties of soils, could be expanded in stances(2.5), Subtopicswithin a majorarea varied breadth and depth for a second-level or derivative (D) widelyin ranking,i.e., undercarbon; canopy char. course. Member(s)of a family of concepts could be ex- acteristics and CO, uptakewere consideredmore panded for a course at the third level of complexity importantthan ambientlevels, trends, and ferti. (D’) if additional expansion for specialization in the lization with CO2. subject is desired. Mostinstitutions surveyedoffer coursesin crop physiologywhich are taughtprimarily at the gradu- A plan for the organization and offering of courses in ate level. Mostrespondents felt that a dual level crop science, on a conceptual basis, was implementedat (senior-graduate)course in cropphysiology, with Iowa State University in 1964. One derivative course plant physiologycourse prerequisite, was most from the introductory course was in the area of physi- desirableas the first cropphysiology course. ology and management termed Crop Growth and If the undergraduatecurriculum in agronomyis Culture. Dr. Mitchell (1970) published the textbook, to be basedon conceptualcourses, we suggest Crop Growth and Culture, to support this new course. that a coursein crop physiologyshould be in- Because this was a major adjustment at the time, tradi- cluded. tional patterns seemed to mittigate against titling the course Crop Physiology as desired. Mitchell probably Additional index words: Conceptualcourses, Cropscience, Agronomycourses. titled his book with the same restraint. A course called Principles of Crop Physiology is currently taught at Iowa State University for majors in agronomy, with a offerings in agronomy or crop science at plant physiology course prerequisite. COURSELand Grant universities have been examinedand re- This paper deals with developing appropriate content ported to the A-I Division of the American Society of for a course which would be titled Crop Physiology. Like Iowa State, Western Illinois University offers an Agronomy(ASA) 3. In their survey they found the fol- lowing. (1) Generally, content of undergraduate courses undergraduate-graduate level course in crop physiology in crop science was organized with emphasis on a crop (i.e., cotton or tobacco production) or a group ’Contribution fromDep. of Agric., WesternIllinois Univ., related crops (i.e., grain or cereal crops, forage crops, McComb,IL 61455and AgronomyDep., IowaState Univ., Ames,IA special crops, or "fiber and oil" crops). Except for 50011.Journal Paper No. 48, College of Agriculture,Iowa State Univ. 2 Visiting professorand professor of agronomy,Univ. of Florida plant breeding, few courses were organized on a con- andIowa State Univ.,respectively. ceptual basis. (2) Crop oriented courses appeared 3R. L. Mitchelland F. P. Gardner.1963. A new subject matter ar- lead to redundance due to the commonalityof principles rangementfor field cropcourses, p. 126.Agron. Abstr. 59 JOURNALOF AGRONOMICEDUCATION, VOL. 10, 1981 titled Advanced Crop Science. Mitchell’s textbook, Table2. Detailedoutline andpeer rating of proposed Crop Growthand Culture, is required. coursetopics in CropPhysiology Wedesired peer appraisal of content and level of the 2.1 I. Introduction proposed course, outlined in Table 2. To accomplish 2.0 A. Crop Physiology--An emerging science this, a questionnaire was sent to crop physiologists in 1.5 B. Dynamicrelationships of growth and yield the ASAin August 1977. Responses to a series of ques- 2.9 C. Distinction between crop physiology and plant physiology tions and the ranking of topics in the course outline as 2.1 n. Growth and development 1.6 A. Definitions to relative importancewere requested. 2.1 B. Cells, tissues, organs, and plants 2.6 C. Kineticsofgrowth 2.7 D. Allometry RESULTS AND DISCUSSION 1.7 E. Meristems and related crop development(tillering, branching, rooting) The percentage return on the questionnaire was about 2.4 F. Ontogeny and morphogenesis 2.2 G. Internal and external factors affecting growth 60°70 (28/50). Rankingof majortopics or the broadsub- 2.1 H. Differentiation divisions of the proposed Crop Physiology course is 2.1 I. Factors affecting differentiation given in Table 1. 1.9 J. Growth-differentiationcorrelations Carbon,partitioning, plant stresses, photosynthesis, 2.5 In. Growthsubstances 2.1 A. Classification and terminology andlight received the highest rating of all majortopics 3.1 B. Classical work and historical (between 1.8 and 2.0). Growthsubstances received the 2.5 C. Auxins and crop responses lowest rating (2.5). Mineral nutrition was ranked2.2 2.4 D. Gibberellins and crop responses 2.7 E. l(inins and crop responses "important" with some comments suggesting that 2.8 F. Inhibitors/retardants and crop responses mineral nutrition could or should be taught in soil sci- 2.9 G. Ethylene and other crop substances ence. Likewise, there were commentssuggesting that 2.8 H. Defoliants and dessicants 2.5 I. Agriculturalapplications growth regulation is more applicable to horticulture 2.1 1. Rooting and/or weed science and could be omitted from Crop 2.3 2. Thinning 2.5 3. Growth modification Physiology. No respondents suggested that photo- 2.4 4. Fruiting modification synthesis and related areas (light, carbon, respiration, 2.2 IV. Mineral nutrition and partitioning of assimilates) be omitted in the pro- 2.1 A. Requirement byplants posed course. However, there were numerous comments 2.1 B. Transport 2.6 1. Outer and freespace as to the nature or kind of coverage these topics should 2.5 2. Active and passive movement receive. Most respondents felt that photosynthesis and 1.8 3. Movementof organic and inorganic substances in plant tissues related topics should be treated at the plant community 2.3C. Metabolism of minerals 2.6 1. Uses in plant processes level rather than at the cellular level. Several suggested 2.4 2. Biological nitrogen fixation that a plant physiology course should be required as a 2.0 D. Nutrition, crop yield, and quality 2.0 E. Root growth and development prerequisite to the proposed crop physiology course. 1.6 G. Root system architecture as related to growthand yield Respondentsapparently felt that students should have a 2.0 V. Light backgroundin the biochemical and cellular aspects of 1.5 A. Energy budget plant physiology before enrolling in a course in crop 1.9 B. Propertiesoflight physiology, represented by the proposed outline. Crop 2.3 C. Pigments: Action and absorption spectra 2.3 D. Control mechanisms--Seedgermination, flowering, other scientists could then concern themselves with photosyn- 1.8 Vl. Carbon thesis and other physiological phenomenaat the canopy 2.3 A. Ambient levels and CO2trends or communitylevel. 1.5 B. Carbon sources and availability Table 2 presents respondent rankings of the sub- 1.5 C. Canopy features and CO2uptake 1.7 D. Canopy ventilation--Natural and manipulated tropical componentsof each major topic. Definitions, 2.2 E. CO=fertilization meristems, and growth-differentiation subtopics were 1.9 VII. Photosynthesis 2.3 A. Light and dark phases: Electron transport Table1. Topicaloutline. Peerratings of topicsin a 2.4 B. Energy sinks and emerson enhancement proposedcourse in CropPhysiology 2.3 C. Alternative carboxylation pathways 1.6 D. Crop canopy--Characteristics and CER Ratings~" Topics 1.6 I. LAI 1.6 2. Plantgeometry--Leafangleandorientation 2.1 I. Introduction 1.8 3. Opticalqualities, extinction 2.1 II. Growth and development 1.6 E. Cropresponse to irradiance levels 2.5 ill. Growthsubstances 2.2 IV. Mineral nutrition 2.1 VIII. Respiration V. Light 1.8 A. Mitochondrial 2.0 1.8 B. Photorespiration 1.8 VI. Carbon 1.6 C. C~/C, characteristics: Anatomical, biochemical, physiological 1.9 VII. Photosynthesis 2.6 1. Theoriesoforigin 2.1 Vlll. Respiration 2.3 2. Variation between and amongtaxa 1.8 IX. Partitioning 2.3 3. Alternatives for photorespiration tenuation 1.9 X. Stresses 2.1 XI. Harvest physiology 2.3 XII. Future challenges 1 = very important, 2 = important, 3 = good to know, 4 = of some value, (continued) and 5 = not important. CROP PHYSIOLOGY COURSE 61 Table 2. Continued stood at the cellular level to understand how they in- fluence crop development and yield. Subtopics under 1.8 IX.

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