Plant Physiology

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.

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

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:

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

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

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