Biomass and Photosynthetic Efficiency of Allium Species Grown in Elevated Carbon Dioxide Levels, with Differing Plant Densities
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BIOMASS AND PHOTOSYNTHETIC EFFICIENCY OF ALLIUM SPECIES GROWN IN ELEVATED CARBON DIOXIDE LEVELS, WITH DIFFERING PLANT DENSITIES AND HARVEST SCHEMES By AMANDA LYNN BROOME, B.S., M.S. A DISSERTATION IN AGRONOMY Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Ellen Peffley Craig Bednarz Leslie Thompson David Wester Paul Pare´ Stephen Maas Fred Hartmeister Dean of the Graduate School August, 2009 Copyright 2009, Amanda Lynn Broome Texas Tech University, Amanda Broome, August 2009 ACKNOWLEDGEMENTS I have such gratitude for Dr. Ellen Peffley who has been my advisor and mentor during my college career. Dr. Peffley taught me the importance of work ethic, introduced me to research, and taught me how to teach. Most importantly, Dr. Peffley modeled self-worth, confidence, and endurance. Thank you to my committee members, Drs. Leslie Thompson, Craig Bednarz, Paul Pare´, and Stephen Maas for your support, classes, and guidance throughout my Ph.D. research. The last member, Dr. David Wester, thank you for the many hours you spent with me working on Allium data with the occasional educational (range or wildlife) story in between. Special thanks to Dr. Ellen Peffley’s lab, my peers, Leah Crosby, Kara Howard Thompson, Nicole Pape, Jim Brown, Jeff Thatcher, and Hema Singh. Thank you to Dr. Leslie Thompson’s lab, especially Kim Kuper and Ana Marie Luna. I have enjoyed working with plant growth chambers located at the Plant and Soil Sciences Department University Greenhouse. The greenhouse, Judith Wilmington, and the greenhouse crew throughout the years have been a second family for me, thank you. Thanks to Dr. Richard Gale for spectrophotometer assistance and Dr. Holladay and his lab for fluorometer assistance. The Plant and Soil Science Department and staff throughout the years have worked hard to help me during my education. Thank you to Dr. Thomas Thompson, Dr. Dick Auld, Dr. Richard Zartman, Pat Kingston, Emily Saiz, Sandy Rogers, and Sylvia Garcia. Thank you to Dr. Cynthia McKenney and Amber Bates for your support, advice, work ethic, and friendship. ii Texas Tech University, Amanda Broome, August 2009 To my family, thank you for making me who I am and putting up with me! Mom, Dad, and Allison, thank you for your encouragement and advice. Thank you to Julie, Zoe and Hannah for helping me through everything in life; these girls are always learning and so am I. Lastly, special thanks to my friends and family, near and far, for their loving spirit. iii Texas Tech University, Amanda Broome, August 2009 TABLE OF CONTENTS ACKNOWLEDGEMENTS………………………………………………………………………ii ABSTRACT…………………………………………………………………………………….viii LIST OF TABLES……………………………………………………………………………......x LIST OF FIGURES……………………………………………………………………………...xi LIST OF ABBREVIATIONS ……………………………………………………………………ix CHAPTER I. REVIEW OF THE LITERATURE Introduction………………………………………………………………………1 History and Culture……………………………………………………………….3 A. cepa…………………………………………………………………….4 A. fistulosum………………………………………………………………5 A. schoenoprasum………………………………………………………...6 Allium Species Biology…………………………………………………………...7 A. cepa…………………………………………………………………….7 A. fistulosum………………………………………………………………9 A. schoenoprasum………………………………………………………...9 Density Studies…………………………………………………………………...10 Field Crop Experiments………………………………………………….10 Onion Experiments………………………………………………………11 Spectral Absorbance……………………………………………………..12 iv Texas Tech University, Amanda Broome, August 2009 Plant Growth in Response to Elevated Carbon Dioxide Levels………………...13 Biomass Effects………………………………………………………….14 Quantification……………………………………………………………16 Chlorophyll Fluorescence………………………………………..16 Photosynthetic Pigments…………………………………………17 Carbon/Nitrogen…………………………………………………18 Hydroponics and Controlled Environment………………………………………21 Research Objectives……………………………………………………………...22 Literature Cited…………………………………………………………………..23 II. BIOMASS AND PHENOLOGY OF ALLIUM SPECIES GROWN AT TWO CARBON DIOXIDE LEVELS, THREE PLANT DENSITIES, AND THREE HARVEST SCHEMES Abstract…………………………………………………………………………..31 Introduction……………………………………………………………………...32 Materials and Methods…………………………………………………………...34 Plant Media………………………………………………………………34 Plant Material…………………………………………………………….34 Media and Material Support……………………………………………..35 Experimental Design……………………………………………………..36 Sample Randomization…………………………………………………..37 Growing Parameters……………………………………………………...37 v Texas Tech University, Amanda Broome, August 2009 Spectrometer Reading……………………………………………………38 Equipment………………………………………………………..38 Procedure………………………………………………………...38 Harvests………………………………………………………………….39 Data Analyses……………………………………………………………40 Results and Discussion…………………………………………………………..40 Spectral Absorbance……………………………………………………..40 Weekly Harvests…………………………………………………………43 Bi-monthly Harvests…………………………………………………….49 One-time Harvest………………………………………………………..62 Cumulative Harvest Comparison………………………………………..73 Conclusion………………………………………………………………………76 Literature Cited………………………………………………………………….77 III. PHOTOSYNTHETIC EFFICIENCY AND PHOTOSYNTHETIC PIGMENTS OF ALLIUM FISTULOSUM GROWN AT THREE CARBON DIOXIDE LEVELS HARVESTED BI-MONTHLY Introduction……………………………………………………………………...78 Materials and Methods…………………………………………………………..78 Plant Media………………………………………………………………79 Plant Material…………………………………………………………….79 Experimental Design……………………………………………………..80 vi Texas Tech University, Amanda Broome, August 2009 Growing Parameters……………………………………………………..80 Harvests………………………………………………………………….81 Fluorescence Measurements……………………………………………..81 Chlorophyll and Carotenoid Extraction…………………………………82 Carbon and Nitrogen Analysis……………………………………..........83 Data Analyses……………………………………………………………84 Results and Discussion…………………………………………………………..84 Conclusion……………………………………………………………………….90 Literature Cited………………………………………………………………….91 IV. OVERALL CONCLUSIONS AND IMPLICATIONS………………….…………90 APPENDIX A: PHOTOSYNTHETIC PIGMENTS………………………………………….95 B: RANDOMIZED TREATMENTS ON TRAY……………………………….96 vii Texas Tech University, Amanda Broome, August 2009 ABSTRACT This research evaluated the effect of carbon dioxide (CO2) level, plant density, Allium species phenology, and harvest scheme on edible biomass of green salad onions. The ontogeny of A. fistulosum, A. cepa, and A. schoenoprasum grown at 10, 15, and 20-mm spacings harvested weekly and bi-monthly was compared to plants harvested once at 70 days after planting (DAP). -1 -1 Plants were grown in ambient (~400 µL•L ) or elevated (1200 µL•L ) CO2 levels. Weekly removal of shoots began 28 DAP with leaves removed 5-cm above planting surface; destructive harvest was 70 DAP. Leaves harvested from Allium grown in 1200 µL•L-1 weighed more at 28 -1 DAP than leaves grown in ~400 µL•L CO2; there was no difference in leaf weight of Allium -1 -1 grown in ~400 µL•L and 1200 µL•L CO2 for the remaining harvests. At 20-mm spacings, leaves harvested from A. cepa weighed the most; leaves harvested from chives weighed the least. The species and spacing producing a large amount of biomass at one harvest is A. fistulosum harvested 70 DAP; the species and spacing selected is A. cepa grown at 20-mm for biomass desired over time. It has been observed in our research that plants grown in elevated CO2 have initial increase in shoot biomass, but as plants age, chlorosis and necrosis was evident on leaves. -1 Allium fistulosum was grown in 400, 1200, and 2000 µL•L CO2 in the same manner above. Leaves from four harvests were analyzed for photosynthetic efficiency (fluorescence yield), photosynthetic pigments (chlorophyll a, b, and carotenoids), and C:N. Leaves from plants grown in each treatment were photosynthetically efficient; chlorophyll was higher in leaves grown in -1 1200 and 2000 rather than 400 µL•L CO2 at 28 DAP. Chlorophyll amounts decreased in plants viii Texas Tech University, Amanda Broome, August 2009 grown in both elevated CO2 levels over 70 days while it increased in leaves grown in ambient at 35 and 49 DAP, then decreased at 70 DAP. A. fistulosum plants grown in elevated CO2 levels, although photosynthetically efficient, had reduction of N and an increase of carbohydrate accumulation in the leaves. Elevated CO2 levels do not increase biomass of Allium, but do not cause decreases in biomass weight; however, plants grown in elevated CO2 appeared more chlorotic due to reduced N in leaves. ix Texas Tech University, Amanda Broome, August 2009 LIST OF TABLES 2.1. Cumulative shoot weight of A. fistulosum, A. cepa, and A. schoenoprasum grown in 400 and 1200 ppm CO2 averaged across three spacings and harvested one-time, bi- monthly, and weekly over 70 days………………………………………………………………………………………74 2.2. Cumulative edible plant weight of A. fistulosum, A. cepa, and A. schoenoprasum grown in 400 and 1200 ppm CO2 averaged across three spacings and harvested one-time, bi-monthly, and weekly over 70 days…………………………………………75 x Texas Tech University, Amanda Broome, August 2009 LIST OF FIGURES 1.1. Absorption spectra of chlorophyll a and b, represented by A and B respectively………19 1.2. Visible spectrum of β-carotene…………………………………………………………..20 2.1. Spectral absorbance of three Allium species grown at 10, 15, and 20-mm spacings in -1 2 -1 elevated (1200 µL·L ) CO2 and ~650 µmol m s ……………………………………...42 2.2. Allium shoot weights/plant grown in ambient and elevated (400 and 1200 µL·L-1) CO2 at each of 7 harvests. CO2 level means followed by the same letter were not significantly different across harvests (P>0.05, protected LSD), n = 54. Harvest 28 and 56 DAP are significantly different (noted