growth dynamics of rice seedlings and their

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GROWTH DYNAMICS OF RICE SEEDLINGS AND THEIR RELATIONSHIP TO THE PHENOTYPE FOR YIELD

Thesis for M. Phil in Biotechnology, under Faculty of Science, University of Pune

Submitted by P. Kamalraj Under the guidance of Prof. V.Sitaramam

Department of Biotechnology University of Pune, Pune -411 007. January, 2007

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Acknowledgements I am extremely grateful to Prof. V. Sitaramam, my thesis supervisor for his outstanding guidance at every stage of this thesis. Prof. Sitaramam supported and encouraged at every stage, which is largely responsible for the work described in this thesis. I would like to thank Prof. Sujata Bhargava for her useful discussions at every stage of my experimental work and manuscript preparation. She allowed me to use the green house facility to do the preliminary experiments with hybrid growth. I thank Prof. H. Bhate, Department of Mathematics, Prof. B.K. Kale, Department of Statistics, Prof. S.P. Modak, Department of Zoology, University of Pune for their useful discussions and several suggestions they gave on the manuscript. Prof. N.V. Joshi kindly provided the programme for energy partitioning model to Prof. Sitaramam, which was included in Appendix A and B. I thank Prof. C.V.Dharmadhikari for his advice in vibration measurements. I would like to thank Dr. R. Bhate for her lead experiment with rice that gave the initial logic of this thesis. I would like to thank my colleague Shilpa Pachapurkar with whom I participated in some of the initial experiments and she introduced me to several laboratory techniques which are described in this thesis. I also thank Dr. Trupti Gokhale and Nitin S.Wahukar for extending a helping hand in times of requirement. Mr. .Milner helped with the dendrogram analysis for which I am grateful. Financial assistance from the Indian Space Research Organization, India, is gratefully acknowledged. I thank the Heads, both past and present of the departments of Biotechnology and Botany for the use of facilities. I am grateful to the Botany department faculty for permitting me to complete my M. Phil. course work in that department. I thank all the faculty members teaching and non-teaching staff of the two departments for the timely help.

P. Kamalraj

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CREDITS The following figures and tables are reproduced from the work from our laboratory included here for the sake of a comprehensive statement of the work achieved as relevant to the thesis. I particularly thank Prof. V. Sitaramam for explicitly permitting me to do so.

Chapter

Fig/Table

Credits

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Fig 2.1

Directorate of Rice Research (DRR), Hyderabad

Fig 2.2

Collaboration with Shilpa P.

Fig 2.6

A. Lead experiment by Dr. R. Bhate; Inset for Fig. 2.6 A and B-F were done by myself with Shilpa P.

Fig 2.12

Prof. V. Sitaramam helped by M. Milner.

Fig 2.13

Prof. V. Sitaramam helped by M. Milner.

Table 2.1

DRR and collaboration with Shilpa.

Appendix: A

Fig A1.

Prof. V. Sitaramam.

Appendix: B

Fig B2

Shilpa P.

Fig B5

Shilpa P.

Fig B6

Myself with Shilpa P.

Fig B7

Myself with Shilpa P.

Fig B8

Myself with Shilpa P.

Please note that each chapter and appendix is written as independent text and symbols defined wherever required. Therefore a common listing is not prepared, as there is possible overlap in rather similar models. However, in order that the text is read independently, figures from other parts are reproduced while keeping the old numbers, for convenience.

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Contents

Chapter

Pages

1

Introduction

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2

Respiration hastens maturation and lowers yield

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in rice. Appendix A:

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Appendix B: Evaluation of growth models in

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plants. Appendix C. Variation in plant growth:

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assessment by models. 3

Hybrid seeds: a physiological characterization

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CHAPTER 1 General Introduction

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1.1 General Introduction Traditionally, two problems face the agronomist. One relates to prediction of yield in a crop plant. The second relates to handling variation in the data which could be astoundingly large. To develop a good variety, one needs a good predictor in selecting the parents. The plant breeding approach requires some clear definition of the phenotype. As plants live at the mercy of the environment in terms of availability of water, temperature, sun light and many other soil parameters, optimization of any one could create a conflict with the other. Consequently much of plant breeding is by trial and error, which makes it both expensive and time consuming. The advent of genetic engineering held much promise and yet one suspects that its performance will not far exceed our understanding of the physiology of the plant. Variable environment ensures that the plant has intrinsic capability to modify its progeny and keep its capacity for variation as much as possible. This could possibly be the basis of residual variation which relates to variation that cannot be reduced regardless of the extent of selfing. In this thesis, I have taken the route that if a variety of a crop plant is characterized for its seed, shoot and root characteristics and growth rates in as much detail as possible by thousands of replicate measurements in time and define the growth characteristics, the growth related parameters could be defined accurately which can be contrasted with the known behaviour of these varieties in terms of larger phonological traits and yield. From this one could ascertain what physiological parameters are relevant for prediction of yield and what contribute to variance most. Further, hybrid seeds have come to stay as the method of enhancing yield, which require that the male sterile lines are used for ensuring true hybrids and not contaminates due to selfing. I also examined in known sets of rice hybrid and parent lines the physiological behaviour if it would help ascertain the quality of hybrid seeds in terms of their production by physiological methods. I report here data indicative of a quantitative definition for yield based on seed respiration and methodology to overcome interference due to variation in the underlying

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processes. I also examine a variety of growth models for their usefulness as I also examine the nature of variation in the variables. Lastly I determine the energy characteristics of the parents in the production of hybrids which throws interesting light on the physiology of male sterile lines, which in turn could have an impact in assessing the quality of hybrid seed production. The chapters and the appendices are written in the style of complete manuscripts to enhance their readability independently. Concluding remarks Major preoccupation is the variation among plants however inbred they are. The care taken in experimental conditions, however obsessive, did not reduce the variation beyond a certain level. From the point of view of a plant it is quite meaningful. Since the onset of monsoon would not be predetermined except in a gross way, a rice plant with a life of 90 – 150 days could well miss out most of the season to its own detriment. What is the obvious solution at the level of germ plasm and nits evolutionary origins? Obviously the plant that can maintain the largest variation has the highest odds for survival against their widest environmental variation. The ability to maintain large variation in a population at the level of germ plasm must have basis in individual plant population traceable to even individual seeds. That is the essence of variation, irreducible in our hands beyond a level. Thus causally related meristematic events showed excellent correlation across the life of an individual plant even when various stages of growth of various parts did not. Thus, seed respiration and germination showed a correlation which would be lost by routine statistical methods whereas in a dendrogram the message was very clear. The story of variation in plants has no finale. Hybrid vigour, really a statistical statement rather than a definitive result since one has to carefully choose the right parents, more by hunch than by science, led to the idea of hybrid seeds. The male sterile seed technology ensured the market viability as well as hybrid nature of the seed and there is a felt need for methods of identification beyond the genetic markers and finger printing since identification of parents does not guarantee the hybrid seed ( in the technical sense) and merely guarantees that, like any seed, they are hybrids. In the very first chapter I outlined a caveat that, all other things equal, seed respiration and yield

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would be related by connection between life stages. This rule is inapplicable in the case of hybrids since other control mechanisms underlie hybrid vigour, a riddle yet to be solved. Thus the careful stance I have taken while formulating the first chapter paid dividends in the last chapter on hybrids as it permitted us to think afresh for a different mechanism by which yield is again forecast or assured. Respiration remained the unknown element for a long time in plant physiology. Our own awakening was helped by the seminal observations of Richard’s in his paper on photosynthesis not being the basis of enhanced plant productivity in the last several decades. Energetics interconnected via developmental biology seems to be the basis of this all important yield in plants, deeply satisfying for a biologist with an eye for the complex mechanisms that under lie the structure and function of the organisms.

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