Dust Bowl ---> Could this Happen Again?? Figure 37.1 Could this happen again?

Soil horizons A horizon B horizon Figure 37.2 Soil horizons C horizon

Cation exchange in soil Soil particle – – K+ K+ – – – – – – – Ca2+ Ca2+ Mg2+ K+ H+ H2O + CO2 H2CO3 HCO3– + H+ Figure 37.3 Cation exchange in soil Root hair Cell wall

Land subsidence caused by excessive removal of groundwater Figure 37.4 Land subsidence caused by excessive removal of groundwater Sinkhole in Florida Land subsidence in California

Contour tillage helps reduce soil erosion Figure 37.5 Contour tillage

Hydroponic culture - used by researchers to determine which chemical elements are essential TECHNIQUE Figure 37.6 Hydroponic culture Control: Solution containing all minerals Experimental: Solution without potassium

The 17 Essential Elements = Micro- and Macro- Nutrients

Healthy Phosphate-deficient Potassium-deficient Nitrogen-deficient The most common mineral deficiencies, as seen in maize leaves Healthy Phosphate-deficient Potassium-deficient Figure 37.7 The most common mineral deficiencies, as seen in maize leaves Nitrogen-deficient

Deficiency warnings from “smart” plants Figure 37.8 No phosphorus deficiency Beginning phosphorus deficiency Well-developed phosphorus deficiency

The role of soil bacteria in the nitrogen nutrition of plants Atmosphere N2 N2 Atmosphere Soil Nitrate and nitrogenous organic compounds exported in xylem to shoot system N2 Nitrogen-fixing bacteria Denitrifying bacteria H+ (from soil) NH4+ Soil NH3 (ammonia) NH4+ (ammonium) NO3– (nitrate) Ammonifying bacteria Nitrifying bacteria Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants Organic material (humus) Root

Root nodules on legume plants Bacteroids within vesicle Nodules Figure 37.10 Root nodules on legumes Roots 5 µm (a) Pea plant root (b) Bacteroids in a soybean root nodule

Development of a soybean root nodule Rhizobium bacteria Infection thread 1 Chemical signals attract bacteria 2 Bacteroids form Bacteroid 1 Infected root hair Dividing cells in root cortex 2 Development of a soybean root nodule Dividing cells in pericycle Developing root nodule Bacteroid 3 4 Figure 37.11 Development of a soybean root nodule 3 Nodule forms 4 Nodule develops vascular tissue Nodule vascular tissue Bacteroid

(b) Endomycorrhizae Arbuscular mycorrhizae Epidermis Cortex Mantle (fungal sheath) 100 µm Endodermis Fungal hyphae between cortical cells Mantle - fungal sheath (a) Ectomycorrhizae (colorized SEM) Epidermis Cortex 10 µm Cortical cells Endodermis Figure 37.12 Mycorrhizae Fungal hyphae Fungal vesicle Casparian strip Root hair Arbuscules Plasma membrane (LM, stained specimen) (b) Endomycorrhizae Arbuscular mycorrhizae

In endomycorrhizae, microscopic fungal hyphae extend into the root Epidermis Cortex 10 µm Cortical cells Endodermis Fungal hyphae Fungal vesicle Casparian strip Root hair Arbuscules Figure 37.12b Mycorrhizae Plasma membrane (LM, stained specimen) Arbuscular mycorrhizae (endomycorrhizae)

Unusual nutritional adaptations in plants Figure 37.14 Unusual nutritional adaptations in plants Staghorn fern, an epiphyte

Unusual nutritional adaptations in plants Figure 37.14 Unusual nutritional adaptations in plants Mistletoe, a photosynthetic parasite

Unusual nutritional adaptations in plants Host’s phloem Dodder Haustoria Figure 37.14 Unusual nutritional adaptations in plants Dodder, a nonphotosynthetic parasite

Unusual nutritional adaptations in plants Carnivorous plants Figure 37.14 Unusual nutritional adaptations in plants

Unusual nutritional adaptations in plants Carnivorous plants Figure 37.14 Unusual nutritional adaptations in plants Pitcher plants

Unusual nutritional adaptations in plants Carnivorous plants Figure 37.14 Unusual nutritional adaptations in plants Sundews

Review NO3– (nitrate) N2 N2 (from atmosphere) (to atmosphere) Nitrogen-fixing bacteria H+ (from soil) Denitrifying bacteria NH4+ NH3 (ammonia) NH4+ (ammonium) NO3– (nitrate) Ammonifying bacteria Nitrifying bacteria Organic material (humus) Root

You should now be able to: Define soil texture and soil composition. Explain why plants cannot extract all of the water in soil. Define cation exchange and describe how plants can stimulate the process. Discuss the problems of topsoil erosion and farm irrigation in arid regions; suggest actions that can help mitigate these problems. Distinguish between and list the macronutrients and micronutrient.s

Explain how a nutrient’s role and mobility determine the symptoms of a mineral deficiency. Summarize the ecological role of each of the following groups of bacteria: ammonifying, denitrifying, nitrogen-fixing, nitrifying. Describe the basis for crop rotation. Distinguish between ectomycorrhizae and arbuscular mycorrhizae. Describe the adaptations for nutrition of parasitic, epiphytic, and carnivorous plants.