Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University; Biology Department; Collegeville, MN 56321; (320) 363 - 2782; (320) 363 - 3202, fax; ssaupe@csbsju.edu |
Leaf Margin Analysis, Or, Are Leaves Good Predictors of Climate?
Objectives: The purpose of this lab is to:
Introduction:
Since plants are stationary they must respond
developmentally, and ultimately evolutionarily, to their environment. As a
result, it's not surprising that leaf morphology (shape) has been shown to be
related to climate. For example, some the following correlations have been
reported (Wiemann et
al, 1998): (a) leaf length is directly related to the mean annual
temperature (MAT); (b) leaf area is directly correlated to both mean annual precipitation (MAP) and
MAT; and (c) leaf width is directly correlated with MAP. Thus, leaves are longer
and larger in climates with warmer
temperatures and higher rainfall.
Another interesting observation that was first reported about 100 year ago is that woody deciduous plants having leaves with toothed margins (termed serrate) predominate in temperate climates while species with smooth (termed entire) leaf margins predominate in frigid (arctic, montane), dry (or saline), and tropical climates. This relationship has been used to derive a mathematical model for predicting MAT. This model has been used to predict past climate by analyzing the leaf margins of fossil plants.
It is not clear why there should be such a strong correlation between leaf margin and temperature. A recent analysis suggests that serrated margins provide regions of quicker photosynthesis in cooler conditions (Royer & Wilf, 2006).
Wiemann et al. (1998) and Wilf (1997) report that the following equations have been derived to predict MAT (in degrees C) or MAP (in cm) from leaf margin structure (% is expressed as a whole number, not a decimal fraction):
The purpose of today's lab is to test the accuracy of these models for our area.
Pre-Lab Study:
Print, read, and bring to class a copy of this
exercise.
Complete Table 1 by locating the data for our area for mean annual temperature (MAT) and mean annual precipitation (MAP). These data can be obtained from a variety of web-based sources such as the Midwest Regional Climate Center (click on: Climate of the Midwest/Climate Summaries). If you need to convert unit, there are many web sites that will help.
Table 1. Climate Data for Central Minnesota | ||
MAT | deg F | deg C |
source: | ||
if web site, date accessed: |
Table 2. Predicted % of woody species in central Minnesota with entire leaf margins | |
Model | Predicted % with entire leaves |
Equation 1 | |
Equation 2 | |
Equation 3 | |
Equation 4 | |
Equation 5 | |
Mean % entire margins | |
Predicted % serrate margins |
Before lab begins, send to me an email that
includes Table 1 & 2. In addition, be sure to record these
data on the lab handout.
For each of your assigned species, bring to class: (a) an image of a characteristic leaf of each species that clearly shows the leaf margin; (b) label each image with the species; and (c) indicate if the leaf is serrate or entire (see methods. note - you may have to find a high resolution image for some). Most of this information can be obtained from sources such as the USDA Plants Database, Flora of North America project site, or books of images such as the Illustrated Guide to Accompany Gleason & Cronquist's Manual of Plants of NE United States and Canada. Images are available in this site or found through a Google "Image" search or other.
Methods:
Once in lab, we will examine herbarium specimens and the
images obtained by your lab mates to complete Table 4. For a leaf to be
considered serrate, the tooth must be an extension of a vein (vascular
extension). Lobed leaves, without teeth, are considered entire. In other words, veins should run into the teeth. Do not
count "spines," as in holly, as teeth. Once you
have collected your data, complete the summary data tables (5, 6 & 7).
It might be easiest to paste your data into an Excel spreadsheet to complete the
necessary calculations.
Table 4. Characteristics of leaves of deciduous woody plants in Central Minnesota | |||
Species | Native to central Minnesota (1 = yes; 0 = no) | Margins (toothed = 0; entire = 1) | |
1 |
Acer negundo � Box elder |
||
2 |
Acer platanoides � Norway maple |
||
3 |
Acer rubrum � Red maple |
||
4 |
Acer saccharinum � Silver maple |
||
5 |
Acer saccharum � Sugar maple |
||
6 |
Acer ginnala � Amur maple |
||
7 |
Aesculus glabra � Buckeye |
||
8 |
Alnus incana � Speckled alder |
||
9 |
Amalanchier canadensis � Serviceberry |
||
10 |
Amorpha canescens � Lead plant |
||
11 |
Aronia melanocarpa � Black chokeberry |
||
12 |
Berberis thunbergii � Japanese barberry |
||
13 |
Berberis vulgaris � Common barberry |
||
14 | Betula alleghaniensis (=B. lutea) � Yellow birch | ||
15 |
Betula nigra � River birch |
||
16 |
Betula papyrifera � White or paper birch |
||
17 |
Carpinus caroliniana � Blue beech |
||
18 |
Catalpa speciosa � Common catalpa |
||
19 |
Celastrus scandens � Bittersweet |
||
20 |
Celtis occidentalis � Hackberry |
||
21 |
Cornus alternifolia � Pagoda dogwood |
||
22 |
Cornus foemina � Gray dogwood |
||
23 |
Cornus rugosa � Round-leaved dogwood |
||
24 |
Cornus stolonifera � Red osier dogwood |
||
25 |
Corylus americana � American hazelnut |
||
26 |
Corylus cornuta � Beaked hazelnut |
||
27 |
Crataegus sp. � Hawthorne |
||
28 |
Diervilla lonicera � Bush honeysuckle |
||
29 |
Dirca palustris � Leatherwood; |
||
30 |
Eleagnus angustifolia � Russian olive |
||
31 |
Euonymus alatus � Winged euonymus |
||
32 |
Fraxinus americana � White ash |
||
33 |
Fraxinus nigra � Black ash |
||
34 |
Fraxinus pennsylvanica � Green ash |
||
35 |
Gleditsia triacanthos � Honey locust |
||
36 |
Gymnocladus dioica � Kentucky coffee tree |
||
37 |
Ilex verticillata � Winterberry |
||
38 |
Juglans cinerea � Butternut |
||
39 |
Juglans nigra � Black walnut |
||
40 |
Lonicera tartarica � Honeysuckle |
||
41 |
Ostrya virginiana � Ironwood, Hophornbeam |
||
42 |
Phellodendron amurense � Amur cork tree, Cork tree |
||
43 |
Physocarpus opulifolius � Ninebark |
||
44 |
Populus nigra cv. italica � Lombardy poplar |
||
45 |
Populus alba � White or silver poplar |
||
46 |
Populus balsamifera � Balsam popular |
||
47 |
Populus deltoides � Cottonwood |
||
48 |
Populus grandidentata � Large toothed aspen |
||
49 |
Populus tremuloides � Quaking aspen |
||
50 |
Potentilla fruticosa � Cinquefoil |
||
51 |
Prunus americana � Wild plum |
||
52 |
Prunus pensylvanica � Pin cherry |
||
53 |
Prunus serotina � Black cherry |
||
54 |
Prunus virginiana � Chokecherry |
||
55 |
Pyrus malus � Apple |
||
56 |
Quercus alba � White oak |
||
57 |
Quercus bicolor � Swamp white oak |
||
58 |
Quercus ellipsoidalis � Northern pin oak |
||
59 |
Quercus macrocarpa � Bur oak |
||
60 |
Quercus rubra (= Q. borealis) � Northern red oak |
||
61 |
Rhamnus cathartica � European Buckthorn |
||
62 |
Rhus glabra � Smooth sumac |
||
63 |
Rhus typhina � Staghorn sumac |
||
64 |
Ribes cynobasti � Prickly gooseberry |
||
65 |
Ribes lacustre � Swamp currant |
||
66 |
Salix discolor � Pussy willow |
||
67 |
Salix exigua � Sandbar willow |
||
68 |
Salix nigra � Black willow |
||
69 |
Sambucus canadensis � Common elderberry |
||
70 |
Sambucus pubens � Red elder |
||
71 |
Sorbaria sorbifolia � False spiraea |
||
72 |
Sorbus aucuparia � Mountain ash |
||
73 |
Spiraea alba � Meadowsweet |
||
74 |
Symphoricarpos albus - Snowberry |
||
75 |
Symphoricarpos occidentalis � Wolfberry |
||
76 |
Syringa reticulata � Japanese tree lilac |
||
77 |
Syringa vulgaris � Common lilac |
||
78 |
Tilia americana � Basswood, Linden |
||
79 |
Ulmus americana � American elm |
||
80 |
Ulmus pumila � Chinese elm |
||
81 |
Ulmus rubra � Slippery elm |
||
82 |
Viburnum lentago � Nannyberry |
||
83 |
Viburnum rafinesquianum - Arrowwood |
||
84 |
Viburnum trilobum � High-bush cranberry |
||
85 |
Zanthoxylum americanum � Prickly ash |
Table 5. Data Summary | |||
Native | Introduced | Total | |
Species number | |||
Percent of total species | |||
# of species with serrate leaves | |||
# of species with entire leaves | |||
Percent species with serrate leaves | |||
Percent species with entire leaves |
Table 6. Predicted MAT for central Minnesota based on leaf morphology of all woody species, native woody species and non-native species | |||
Model | MAT (◦C) - data from all species | MAT (◦C) - native species data | MAT (◦C) - introduced species data |
Equation 1 | |||
Equation 2 | |||
Equation 3 | |||
Equation 4 | |||
Equation 5 | |||
Mean |
Data & Analysis: Once you have collected your data:
Complete the summary data tables (5 & 6).
Table 7. Chi square goodness-of-fit test comparing native species with serrate and entire margins |
|
null hypothesis: |
|
Observed values: | serrate: entire: |
Expected values: | serrate: entire: |
p value = | |
Conclusion: | The null hypothesis should be: rejected accepted |
Table 8. Chi square 2 x 2 contingency table, comparing leaf margins on native and non-native species | ||
native species | non-native species | |
serrate | ||
entire |
Table 9. Results of chi square 2 x 2 contingency table, comparing leaf margins on native and non-native species |
|
null hypothesis: | |
p value = | |
Conclusion: | The null hypothesis should be: rejected accepted |
Post-Lab Assignment: Write an abstract of this lab. Append to your abstract, typed on a separate sheet of paper not photocopies of this handout, completed copies of tables 5 - 9. In your abstract address questions such as:
References:
Bailey, IW, EW Sinnott (1916) The climatic distribution of certain types of angiosperm leaves. American Journal of Botany 3: 24 - 39.
Leaf Architecture Working Group (1999) Manual of Leaf Architecture. Yale University.
Royer, DL & P Wilf (2006) Why do toothed leaves correlate with cold climates? Gas exchange at leaf margins provides new insights into a classic paleotemperature proxy. Int. J. Plant Sci. 167: 11 - 18.
Sinnott, EW, IW Bailey (1915) Investigations on the phylogeny of the angiosperms. 5. Foliar evidence as to the ancestry and early climatic environment of the angiosperms. American Journal of Botany 2: 1 - 22.
Wiemann, MC, SR Manchester, DL Dilcher, LF Hinojosa, EA Wheeler (1998) Estimation of temperature and precipitation from morphological characters of dicotyledonous leaves. American Journal of Botany 85: 1796 - 1802.
Wilf, P (1997) When are leaves good thermometers? A new case for leaf margin analysis. Paleobiology 23: 373 - 390.
Web Sites:
Checklist of Trees & Shrubs of the College of St. Benedict & St. John's University - SG Saupe
Common Trees & Shrubs of St. John's - SG Saupe
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Last updated:
01/07/2009 � Copyright by SG
Saupe