Objectives of paleobotany

describes the main objectivess of paleobotany and the role of paleobotanist

1. INTRODUCTION TO PALEOBOTANY

2. WHAT IS PALEOBOTANY? Humans are by nature curious, and we are all interested in the Earth on which we live and how various aspects have changed through geologic time. It is natural to wonder about prehistoric life—how these organisms lived, what their patterns of behavior were, and even why they became extinct. the paleobotanist is a plant historian who attempts to piece together the intricate and complicated picture of the history of the plant kingdom.

3. Fossil plants and floras from one period of geologic time are different in size and shape, level of complexity, and abundance from those of other time periods. The most logical explanation for these differences is that the types of plants changed , or evolved , through geologic time. By studying the record of fossil plants, it is possible to assess the time at which various major groups originated , the time each reached its maximum diversity, and, in the case of certain groups, when they became extinct .

4. THE OBJECTIVES OF PALEOBOTANY One of the aspects of paleobotany , which makes it unusual and interesting, is that it is and can be approached from inherently interdisciplinary either a biological or a more geological perspective—or both together. Each perspective presents a variety of questions that are unique to that discipline.

5. 1. RECONSTRUCTING THE PLANTS Because the majority of fossil plants are generally preserved in rocks as disarticulated plant parts. a major aim of paleobotany is to reconstruct the whole plant, that is to say, to put the pieces of the puzzle back together. Once this is accomplished, the research can turn to other areas, such as determining the group of living plants, if any, to which the fossil is most closely related. how did these plants reproduce, and how and what types of propagules were disseminated? Are…. etc

6. 2. EVOLUTION OF PLANT GROUPS Paleobotanists are also interested in the origin and subsequent evolution of major groups of plants and their interrelationships. When did plants first inhabit the Earth and what did they look like? When did the first representatives of different groups of plants first arise? A number of paleobotanists study not only the plants themselves, but also the interactions of the plants with other organisms in the environment, especially the symbiotic interrelationships between plants and other organisms.

7. Can we determine from the fossil record if plants possessed certain features that served to attract pollinators , or produced edible seeds , or whether some plants produced certain chemicals that deterred herbivory ? The answer to all these questions is a resounding YES! There is a multitude of information that can be gleaned from careful examination of the plant fossil record, and the types of information that we can obtain are constantly increasing as more and more research is done on fossil plants.

8. 3. FORM AND FUNCTION IN FOSSIL PLANTS From many plant fossils, it is possible to understand the relationship between form and function in ancient plants, that is, what advantages or limitations are imposed on the growth and development of a plant based on certain biomechanical properties? Studies of this type examine the anatomical and morphological properties of various fossil plants, often using computer simulations to model growth, in an attempt to better understand broad evolutionary patterns of plant growth, as well as changes in growth form through time

9. Biomechanical studies have been especially useful in delimiting adaptations necessary for plants to move onto the land , including upright growth, size limitations, and the nature of the conducting strand, and, once plants became established in terrestrial environments, the influences of gravity and wind on their reproduction, and even aerodynamic features of pollen. Factors such as plant size and form can also be examined over a broad spectrum of plant morphologies and thus offer insights as to why certain plants and plant groups have developed particular anatomical and morphological characteristics.

10. 4. BIOSTRATIGRAPHY AND CORRELATION Paleobotany has also played a key role in many areas of geology, especially in biostratigraphy—placing rock units in stratigraphic order based on the fossils within them . Pollen grains and spores have been extensively used as index fossils in biostratigraphy and in the correlation of rock units, as have various forms of algal cells and cysts. Pollen and spores, as well as megafossils , are especially useful in correlating terrestrial rocks, as these are generally deposited in limited areas (former lakes, ponds, river systems, etc.), making correlation by lithology (i.e., rock characteristics) very difficult.

11. 5. PALEOECOLOGY: PLANTS IN THEIR ENVIRONMENT Paleoecology, the study of past environments , is a rapidly changing field that involves the integration and synthesis of both botanical and geological information. In recent years there has been a concerted effort by many paleobotanists to understand the paleoenvironment of fossil land plants more completely. Paleoecological studies are very important in revealing the diversity of fossil communities inhabiting a geographic area (horizontal variation in floras) at the same time.

12. Analysis of the plants preserved at different levels in these deposits not only documents the partitioning of the habitat among the different plant groups along ecological lines, but also records changes in the depositional environment through time.

13. 6. DETERMINING PALEOCLIMATE FROM FOSSIL PLANTS Understanding climates of the past has become more and more crucial to appreciating the changes occurring on our warming planet today. paleobotany is very important in providing baseline data to reconstruct past climates and in calibrating paleoclimate models based on physical parameters. This area is rapidly expanding, so we will only cover a few of the many ways in which plant fossils can be used to reconstruct paleoclimate :

14. 1. TREE RINGS Data from fossil tree rings ( paleodendrology ) represent an important source of paleoclimate information, in some instances with very fine resolution, for example, major atmospheric disturbances. Based on the changes in radial cell diameter within the tree rings and the variation in ring width, it is possible to extrapolate climate information, which is especially useful when coupled with information from megafossils , microfossils, and the sedimentological record of the site. Taylor and Ryberg (2007) have examined tree rings in Permian and Triassic woods from Antarctica. Based on their analysis using a variety of techniques, they suggest that the small amount of latewood indicates a very rapid transition to seasonal dormancy in response to decreasing light levels at these high polar latitudes.

15. 2. NEAREST LIVING RELATIVE The nearest living relative ( NLR ) method has been in use since the beginnings of paleobotany , particularly when dealing with late Mesozoic or Cenozoic floras, as these are more likely to have close living relatives. The paleobotanist compares as many fossils as possible within a flora to their most closely related extant taxa; the more species in a fossil flora that have NLRs, the more precise the paleoclimate estimate, and the more closely related a fossil taxon is to an extant one, the more precise the method. This method can provide a general estimate of paleoclimate , but is limited by the fact that some fossil taxa do not have the same climatic limitations as their modern counterparts.

16. 3. LEAF PHYSIOGNOMY Leaf physiognomy analysis is a powerful technique that has been widely used in paleobotany to reconstruct Cenozoic paleoclimates . It is based only on angiosperms, however, so its applicability before the Cretaceous is uncertain Physiognomy is the general appearance of a plant, and it has long been known that plant physiognomy, especially leaf physiognomy, can be related to climate. Physiognomy is primarily independent of taxonomy, for example plants with thick water-storing stems and leaves tend to grow in arid regions of the world, even though they may belong to a number of different families of plants.

17. There are presently two methods of leaf physiognomic analysis that are in general use: leaf-area and leaf-margin analysis. Leaf area directly correlates with mean annual precipitation ( MAP ). Leaf-margin analysis (LMA) relies on the relationship between leaf margin (toothed versus entire) and climate. Specifically, the proportion of leaves in the flora with toothed margins can be correlated with mean annual temperature ( MAT ), as toothed leaves are more abundant in wet environments.

18. 4. STOMATAL INDEX The stomatal index (the ratio of the number of stomata to the total number of epidermal cells plus stomata within a given leaf area expressed as percentages) has been widely used in recent years to reconstruct past ρCO 2 levels, as the stomatal index is inversely proportional to atmospheric CO 2 levels.