Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1983 The effects of osmotically-induced water stress and stripe smut (Ustilago striiformis) or flag smut (Urocystis agropyri) on Kentucky bluegrass (Poa pratensis 'Merion') Jeffery Lynn Nus 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 Plant Biology Commons Recommended Citation Nus, Jeffery Lynn, "The effects of osmotically-induced water stress and stripe smut (Ustilago striiformis) or flag smut (Urocystis agropyri) on Kentucky bluegrass (Poa pratensis 'Merion') " (1983). Retrospective Theses and Dissertations. 8950. https://lib.dr.iastate.edu/rtd/8950 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. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help clarify markings or notations which may appear on this reproduction. 1.The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure complete continuity. 2. 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These prints are available upon request from the Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases the best available copy has been filmed. UniversiV Micr^lms International 300 N. Zeeb Road Ann Arbor, Ml 48106 8407114 Nus, Jeffery Lynn THE EFFECTS OF OSMOTICALLY-INDUCED WATER STRESS AND STRIPE SMUT (USTILAGO STRIIFORMIS) OR FLAG SMUT (UROCYSTIS AGROPYRI) ON KENTUCKY BLUEGRASS (POA PRATENSIS 'MERION') Iowa State University PH.D. 1983 University Microfilms Intsrnâtional 300 N. zeeb Road, Ann Arbor, Ml 48106 The effects of osmotically-induced water stress and stripe smut (Ustilago striiformis) or flag smut (Urocvstis agropvri) on Kentucky bluegrass (Poa pratensis 'Merion*) by Jeffery Lynn Nus A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Major: Horticulture Approved: Signature was redacted for privacy. In Charge^f Majef Wori Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1983 il TABLE OP CONTENTS Page I. INTRODUCTION 1 II. REVIEW OF LITERATURE 6 A. Water Deficits 6 1. Application 6 2. Measurement 9 a. Water content 9 b. Water potential 10 3. Effects on plants 19 a. Growth 19 b. Water relations 24 G. Water loss 25 d. Osmotic adjustment and cell wall 32 elasticity B. Disease 38 1. Effects on plants 38 a. Growth 38 b. Water economy 39 2. Leaf smuts 41 III. GROWTH OF WATER-STRESSED POA PRATENSIS INFECTED 44 BY UROCYSTIS AGROPYRI OR USTILAGO STRIIFORMIS A. Abstract 44 B. Introduction 45 C. Materials and Methods 46 1. Nutrient solution studies 48 2. Water stress studies 49 iii Page D. Results 50 1. Nutrient solution effects 50 2, Water stress effects 53 E. Discussion 53 IV. EFFECT OF WATER STRESS AND SYSTEMIC INFECTION 59 BY USTILAGO STRIIFORMIS OR UROCYSTIS AGROPYRI ON THE GROWTH OF TILLERS AND RHIZOMES OF POA PRATENSIS A. Abstract 59 B. Introduction 60 C. Materials and Methods 6l 1. Nutrient solution studies 62 2. Water stress studies 63 D. Results 64 1. Nutrient solution effects 64 2. Water stress effects 67 E. Discussion 70 V. EFFECT OF WATER STRESS AND INFECTION BY USTILAGO 72 STRIIFORMIS OR UROCYSTIS AGROPYRI ON LEAF TURGOR AND WATER POTENTIALS OF POA PRATENSIS At Abstract 72 B, Introduction 73 C. Materials and Methods 74 D. Results 78 E, Discussion 87 VI. COMPARATIVE WATER USE BY HEALTHY AND USTILAGO 91 STRIIFORMIS-INFECTED POA PRATENSIS iv Page A. Abstract 91 B. Introduction 91 C. Materials and Methods 93 1. Water use and efficiency 94 2. Leaf diffusive resistance 95 D. Results 97 E. Discussion 100 VII. CONCLUSIONS 108 VIII. LITERATURE CITED HO IX. ACKNOWLEDGMENTS 1^5 1 I. INTRODUCTION Water is an essential component of plant life and comprises approximately 85 to ^Ofo of the total fresh weight in physiologically active herbaceous plants. Many physiological functions of the plant are impaired when the water content falls much below this level (Turner and Kramer, 1980). Water shortage is more limiting to crop production in the world than any other single factor (Kozlowski, 1968a). Over one-third of the world's cropland receives less than 30 inches of precipitation per year and crop yields are periodically reduced by drought (Townley-Smith and Kurd, 1979)» Drought is a major limiting factor of yields even in tropical regions (Wein et al., 1979). Kramer (I98O) claims worldwide losses in yield from water stress probably ex­ ceed the losses from all other causes combined. It is important to differentiate between the terms drought and water stress to avoid confusion when studying the effects of water deficits on plants. Drought is a meterological event defined as the absence of rainfall for a period of time long enough to cause depletion of soil moisture and damage to plants (May and Milthorpe, I962). The length of time without rain that is necessary to cause injury depends on the kind of plants, the water holding characteristics of the soil in which they are growing, and 2 the atmospheric conditions that affect the rate of evaporation and transpiration (Kramer, I98O). Levitt (1972) describes a "biological stress as "any environmental factor capable of inducing a potentially injurious strain in living organisms". Crafts (1939) suggested that the terra water stress be defined as the state a plant enters when the water potential crosses the zero mark and becomes negative. Although plant water stress always accompanies drought, it may occur in the absence of drought, either because of excessive transpiration or be­ cause water absorption is inhibited by cold soil, an excess of salt in the soil solution, deficient aeration, or injury to root systems (Turner and Kramer, 1980). The degree of dehydration without permanent injury varies widely, depending on the process under consideration, the stage of development, the duration of stress, and the kind of plant (Hsiao, 1973î Begg and Turner, 1976). Because of the overwhelming importance of water for plant growth and development, several books (Kozlowski 1978; 1976a; 1972; 1968a; 1968b; 1964; Kramer 1969? 19^9; Lange et al., 1976; Levitt, 1972; Maximov, 1929î Mussell and Staples, 1979; Paleg and Aspinall, 1982; Rutter and Whitehead, I963; Slatyer, 1967; Slavik, 1974; Turner and Kramer, I98O) and reviews (Boyer and McPherson, 1975» Gates, 1964; Henckel, 1964; Hsiao, 1973; Ilgin, 1957; Kramer, I963; Macklon and Weatherley, 1965; Shaw and Laing, I966; Slatyer, 1957; 3 Vaadia et al., 19^1) have been written. Mechanisms for drought resistance have been reviewed by Ilgin (1957), Levitt (1972), and Paleg and Aspinall (1982). Plant disease is another limiting factor in crop production in addition to shortages of water. Disease is a cause of lowered efficiency or final breakdown in the plants growth and function (Wood, 1953)» The relationship between plant disease and environment is complex. Environ­ mental conditions may predispose potential hosts to invasion by pathogens (Schoeneweiss, 1975b, 1978), affect the growth, distribution, and survival of pathogens (Cook, 1973î Griffin, 1978; Cook and Duniway, I98I), and modify the expression of the disease syndrome (Talboys, I968). Temperature and moisture are the limiting factors for most plant diseases (Miller, 1953)» and either can be decisive in the initiation, development, and spread of disease. The disease becomes serious if both are constantly favor- able. Symptoms of plant disease may include disease- induced water deficits in the host, i.e., the drought syndrome (Talboys, 1968). Disease-induced host water deficits may arise in several ways. Vascular wilt pathogens induce water deficits by producing vascular occlusions, toxic metabolites, host degradation products, or host reaction mechanisms (Dimond, 1970). Disease-induced water deficits also may result from loss of membrane integrity k from the action of toxins or enzymes, or the disruption of host hormonal "balance (Ayres, 1978; Talboys, I968). Pathogen-induced reduction in root growth and subsequent decrease in host root-shoot ratio may lead to host water deficits (Murphy, 1935; Sever, 1937). Finally, dramatic increases in water loss may accompany infection.