Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1980 Physiological observations of maize (Zea mays L.) hybrids differing in photosynthetic capability Mark Lincoln Gaskell Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agricultural Science Commons, Agriculture Commons, and the Agronomy and Crop Sciences Commons Recommended Citation Gaskell, Mark Lincoln, "Physiological observations of maize (Zea mays L.) hybrids differing in photosynthetic capability " (1980). Retrospective Theses and Dissertations. 6785. https://lib.dr.iastate.edu/rtd/6785 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. 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Requests can be made to our Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases we have filmed the best available copy. Uniliversi^ Micrdrilms Intemationêil 300 N. ZEEB ROAD, ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WC1R 4EJ, ENGLAND 8028614 GASKELL, MARK LINCOLN PHYSIOLOGICAL OBSERVATIONS OF MAIZE (ZEA MAYS L.) HYBRIDS DIFFERING IN PHOTOSYNTHETIC CAPABILITY Iowa Stale University PH.D. 1980 University IVIicrofilms I n t0r n sit ions! 300 N. Zeeb Road, Ann Arbor, MI 48106 18 Bedford Row, London WCIR 4EJ, England Physiological observations of maize (Zea mavs L.) hybrids differing in photosynthetiç capability by Mark Lincoln Gaskell A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Department: Agronomy MajorI Crop Production and Physiology Approved : Signature was redacted for privacy. I Charge o^ Ma jor Work Signature was redacted for privacy. B the Major Department Signature was redacted for privacy. For me Graduate College Iowa State University Ames t Iowa 1980 ii TABLE OF CONTENTS Page INTRODUCTION AND BACKGROUND 1 PART I. GROWTH ANALYSIS OF MAIZE HYBRIDS DIFFERING IN PHOTOSYNTHETIC CAPABILITY 5 INTRODUCTION 6 MATERIALS AND METHODS 9 RESULTS 12 DISCUSSION 27 PART II. EFFECTS OF NITROGEN FERTILITY ON PHOTOSYNTHESIS, GROWTH RATE, AND LEAF AREA OF MAIZE HYBRIDS DIFFERING IN PHOTOSYNTHETIC CAPABILITY 30 INTRODUCTION 31 MATERIALS AND METHODS 34 RESULTS AND DISCUSSION 38 PART III. STOMATAL FREQUENCY AND STOMATAL RESISTANCE OF MAIZE HYBRIDS DIFFERING IN PHOTOSYNTHETIC CAPACITY 53 INTRODUCTION 54 MATERIALS AND METHODS 58 RESULTS AND DISCUSSION 61 SUMMARY AfID CONCLUSIONS 66 LITERATURE CITED 69 ACKNOWLEDGMENTS 75 t 1 INTRODUCTION AND BACKGROUND Plant photosynthetic assimilatory processes account for more than 90% of dry matter yield and crop production improve­ ment is closely linked to enhancement of photosynthetic activity per unit land area. One means of increasing photo­ synthesis is through the development of crop cultivars with enhanced photosynthetic efficiency per unit leaf area. This efficiency is believed low relative to its potential and research efforts for more than a decade have been directed toward the possibility of improving intraspecific cultivar photosynthesis. Genotypic variation in photosynthetic rate exists for a number of crop plant species and the assumption has been that dry matter productivity is closely related to photosynthetic rate. Total biological production over a given time period must correspond to net carbon assimilated per unit leaf area minus a dark respiratory component per unit leaf area mul­ tiplied by the total amount of leaf area. In this way, if respiratory activity and total leaf area do not vary, culti­ vars with the highest leaf photosynthesis (carbon dioxide exchange rate [CER]) should exhibit the most rapid growth in dry weight. The economically important yield is usually some propor­ tion of the total dry matter yield. Determination of economic yield, thus, involves further considerations such as* 2 1. Limitations imposed by the size of the economic yield organ (as grain, tuber, etc.); 2. Differences in efficiency of translocating assimilates to economic products; 3. Different patterns of partitioning of assimilates into different plant parts; 4. Variation in organ respiratory activities, activity of competitive, nonproductive "sinks" for photosyn- thetic assimilates (such as roots, stems, stem bases, or tillers); and other possible sources of dry weight apportioning variation. Even though highest rates of biological yield accumula­ tion do not necessarily mean higher economic yield, it seems reasonable that greater biological yield potential would pro­ vide a better background for economic yield improvement. Some reports of a good relationship between leaf CER and yield do exist (Akiyama and Takeda, 1975; Brinkman and Frey, 1978), Unfortunately, in the majority of cases neither plant growth rate nor economic yield have consistently been related to leaf CER (Evans, 1975; Nasyrov, 1978). In some cases, a negative relationship between leaf CER and yield has been observed (Evans and Dunstone, 1970; Hanson, 1971; Irvine, 1975; Kaplan and Roller, 1977). Much of the contra­ dictory evidence for a photosynthesis/productivity relation­ ship is thought to be associated with variations in leaf area. 3 In this way, leaf area compensation by lower CER cultivars results in equal or greater total plant CER (Delaney and Dobrenz, 1974; Irvine, 1975). It appears that in addition to leaf area, there is some evidence that dark respiration interacts with leaf CER (Jones and Nelson, 1979). Other factors such as translocation rates, dry matter distributions and other parameters described earlier may also be variable among crop cultivars. Little is known about the growth patterns and other physiological characteristics of crop cultivars which are variable in photosynthetic capability. Knowledge of the mechanisms of differences in CER would be useful in attempting to establish connections between photosynthesis and yield. These mechanisms are not well-understood generally, but it is likely that the reasons for varietal CER variation differ among crop plant species. Physiological mechanisms contributing to CER variation are most likely to differ among the major photosynthetic assimilatory groups, the Cg and C^ carboxylation species. Some studies have investigated mechanisms of varietal CER variation within a crop species, but much less is known about C^ than Cg species (Evans, 1975; Wilson, 1979). Maize (Zea mays L,) is a C^ species and exhibits geno- typic variability in CER capability (Heichel and Musgrave, 1969; Heichel, 1971; Crosbie et al,, 1977). Although some mechanisms of cultivar photosynthetic variability have been 4 investigated in maize, reasons for these CER differences re­ main obscure. As selection programs for CER improvement in maize proceed, it is important to investigate cultivars dif­ fering in leaf CER with regard to other physiological processes. The three studies which follow were directed toward physiological comparisons among high and low-CER maize cultivars. These experiments had three general objectives; 1. To investigate possible vegetative growth pattern differences among high and low CER maize lines; 2. To determine possible advantages or disadvantages pertaining to nitrogen fertility utilization which may be associated with leaf CER; 3. To investigate a possible causal mechanism for leaf CER differences by determining if variation in stomatal frequency or activity is associated with relative leaf CER. 5 PART I. GROWTH ANALYSIS OF MAIZE HYBRIDS DIFFERING IN PHOTOSYNTHETIC CAPABILITY 6 INTRODUCTION In,traspecific variation in carbon-dioxide exchange rate (CER)