Plant Nutrition Ch 37 Physiological adaptation Dogs pee

Plant Nutrition (Ch. 37)

Physiological adaptation Dogs pee on trees…Why don’t trees pee on dogs? NH 3 animal waste plant nutrient

Nutritional needs • Autotrophic does not mean autonomous – plants need… • sun as an energy source • inorganic compounds as raw materials – water (H 2 O) – CO 2 – minerals

Macronutrients • Plants require these nutrients in relatively large amounts – C, O, H, N, P, K, Ca, Mg, S

For what & from where? C macromolecule synthesis CO 2 O macromolecule synthesis CO 2 H macromolecule synthesis & proton pumps H 2 O N protein & nucleic acid synthesis to make all plant proteins soil P nucleic acids, a ATP, phospholipids soil growth establish strong root system in young plants, K stomate water balance soil (ie. carrots) Flowers, control, absorption of water, strong roots, root crops Ca cell wall & membrane regulation soil Cell walls, structure, nutrient and soil conditioner Mg chlorophyll soil S proteins, enzymes soil

Local Long Island soil issues Quartz silica based soils - low in P - can be acid Acid soils bind up mineral ions p. H by adding lime Granite

Micronutrients • Plants require in very small amounts – Cl, Fe, Mn, Bo, Zi, Ni, Mb – primarily cofactors for enzyme function

Nutrient deficiencies • Lack of essential nutrients – exhibit specific symptoms • dependent on function of nutrient • dependent on solubility of nutrient

• Mineral deficiency symptoms depend not only on the role of the nutrient but also on its mobility within the plant. If a nutrient moves about freely, symptoms will show up first in older organs because young, growing tissues have more “drawing power” for nutrients in short supply. For example, magnesium is relatively mobile and is shunted preferentially to young leaves. Therefore, a plant starved for magnesium will show signs of chlorosis first in its older leaves. The mechanism for preferential routing is the source–to–sink translocation in phloem as minerals move along with the sugars to the growing tissues. In contrast, a deficiency of a mineral that is relatively immobile will affect young parts of the plant first. Older tissues may have adequate amounts, which they are able to retain during periods of short supply. For example, iron does not move freely within a plant, and an iron deficiency will cause yellowing of young leaves before any effect on older leaves is visible. • Deficiencies of nitrogen, phosphorus, and potassium are most common. Shortages of micronutrients are less common and tend to occur in certain geographic regions because of differences in soil composition. The symptoms of a mineral deficiency are often distinctive enough for a plant physiologist or farmer to diagnose its cause

Magnesium deficiency • Symptoms Take 2 fertilizer pellets & call me in the morning – chlorosis = yellowing of leaves – Why? What is magnesium’s function?

Chlorophyll Why does magnesium deficiency cause chlorosis? The chlorosis shows up in older leaves first, because plant moves Mg+ to newer leaves. Why?

The role of soils Agronomists really dig dirt! • Plants are dependent on soil quality – texture / structure • relative amounts of various sizes of soil particles – composition • organic & inorganic chemical components • fertility

Importance of organic matter • Topsoil So don’t rake – most important to plant growth your lawn or bag your leaves – rich in organic matter • humus – decomposing organic material » breakdown of dead organisms, feces, fallen leaves & other organic refuse by bacteria & fungi – improves soil texture – reservoir of minerals – organisms • 1 tsp. of topsoil has ~5 billion bacteria living with fungi, algae, protists, insects, earthworms, nematodes

Soil health as a global issue Not taking care of soil health has far-reaching, damaging consequences – 1920’s Dust Bowl – lack of soil conservation • growing the same crop year after year (wheat) • grazing by cattle • bare ground exposed to wind erosion in winter • drought

Soil health as a global issue • Soil conservation & sustainable agriculture – maintaining healthy environment – sustainable production of food supply – economically viable farming industry “A sustainable agriculture does not deplete soils or people. ” – Wendell Berry contour plowing cover crops crop rotation

Fertilizers • “Organic” fertilizers – manure, compost, fishmeal • “Chemical” fertilizers – commercially manufactured – N-P-K (ex. 15 -10 -5) • 15% nitrogen • 10% phosphorus • 5% potassium What are the political, economic, environmental issues? Your next Current event!

Nitrogen uptake • Nitrates – plants can only take up nitrate (NO 3 -) • Nitrogen cycle by bacteria – trace path of nitrogen fixation! root What will the plant use N for?

Soybean root nodules • N fixation by Rhizobium bacteria – symbiotic relationship with bean family (legumes)

Increasing soil fertility • Cover crops Plow it under? Why would you that? – growing a field of plants just to plow them under • usually a legume crop • taking care of soil’s health – puts nitrogen back in soil erosion control, too

Some plant oddities… 2006 -2007

Parasitic plants • tap into host plant vascular system Indian pipe Mistletoe

Plants of peat bogs • High acid environment – most minerals & nutrients bound up & are not available to plants • must find alternative sources of nutrients

Carnivorous plants Sundew Venus fly trap Pitcher plant Are they really carnivores?

Pitcher plant

Uses of peat

Any Questions? ?

Review Questions

1. The inorganic compound that contributes most of the mass to a plant’s organic matter is * A. B. C. D. E. H 2 O. CO 2. NO 32. O 2. C 6 H 12 O 6.

2. You are conducting an experiment on plant growth. You take a plant fresh from the soil and it weighs 5 kg. Then you dry the plant overnight and determine the dry weight to be 1 kg. Of this dry weight, how much would you expect to be made up of inorganic minerals? A. 50 grams B. 500 grams C. 1 kg D. 4 kg E. 5 kg

• we can rule out C, D , and E and because the dry weight of any plant is going to be mostly cellulose ( a polymer of glucose) we can pretty much be assured half of the dry weight is not going to be from inorganic minerals and ions. The only choice that makes any sense at all is 50 grams. No calculations needed

This figure shows the results of a study to determine the effect of soil air spaces on plant growth. Use these data to answer the following question.

3. The best explanation for the shape of this growth response curve is that A. the plant requires air in the soil for photosynthesis. B. the roots are able to absorb more nitrogen (N 2) in high levels of air. C. most of the decrease in weight at low air levels is due to transpiration from the leaves. D. increased soil air produces more root mass in the soil but does not affect the top stems and leaves. E. the roots require oxygen for respiration and growth.

4. Carnivorous plants have evolved mechanisms that trap and digest small animals. The products of this digestion are used to supplement the plant's supply of A. B. C. D. E. energy. carbohydrates. lipids and steroids. minerals. water.

• Are some essential elements more important than others? Explain. No, because even though macronutrients are required in greater amounts, all essential elements are necessary for the plant to complete its life cycle.

• Can a single leaf be used to diagnose all of a plant’s mineral deficiencies? Explain. a. No, because deficiencies of nutrients that are mobile show up first in older leaves, whereas deficiencies in nutrients that are less mobile show up first in younger leaves.