Presentation is loading. Please wait.

Presentation is loading. Please wait.

Transport in Plants 2006-2007.

Similar presentations


Presentation on theme: "Transport in Plants 2006-2007."— Presentation transcript:

1 Transport in Plants

2 Why does over-watering kill a plant?
Transport in plants H2O & minerals transport in xylem transpiration evaporation, adhesion & cohesion negative pressure Sugars transport in phloem bulk flow Calvin cycle in leaves loads sucrose into phloem positive pressure Gas exchange photosynthesis CO2 in; O2 out stomates respiration O2 in; CO2 out roots exchange gases within air spaces in soil Why does over-watering kill a plant?

3 Ascent of xylem fluid Transpiration pull generated by leaf

4 Water & mineral absorption
Water absorption from soil osmosis aquaporins Mineral absorption active transport proton pumps active transport of H+ aquaporin root hair proton pumps H2O

5 Mycorrhizae increase absorption
Symbiotic relationship between fungi & plant symbiotic fungi greatly increases surface area for absorption of water & minerals increases volume of soil reached by plant increases transport to host plant

6 Pressure flow in phloem
Mass flow hypothesis “source to sink” flow direction of transport in phloem is dependent on plant’s needs phloem loading active transport of sucrose into phloem increased sucrose concentration decreases H2O potential water flows in from xylem cells increase in pressure due to increase in H2O causes flow can flow 1m/hr In contrast to the unidirectional transport of xylem sap from roots to leaves, the direction that phloem sap travels is variable. However, sieve tubes always carry sugars from a sugar source to a sugar sink. A sugar source is a plant organ that is a net producer of sugar, by photosynthesis or by breakdown of starch. Mature leaves are the primary sugar sources. A sugar sink is an organ that is a net consumer or storer of sugar. Growing roots, buds, stems, and fruits are sugar sinks. A storage organ, such as a tuber or a bulb, may be a source or a sink, depending on the season. When stockpiling carbohydrates in the summer, it is a sugar sink. After breaking dormancy in the spring, it is a source as its starch is broken down to sugar, which is carried to the growing tips of the plant. A sugar sink usually receives sugar from the nearest sources. Upper leaves on a branch may send sugar to the growing shoot tip, whereas lower leaves export sugar to roots. A growing fruit may monopolize sugar sources around it. For each sieve tube, the direction of transport depends on the locations of the source and sink connected by that tube. Therefore, neighboring tubes may carry sap in opposite directions. Direction of flow may also vary by season or developmental stage of the plant. On a plant… What’s a source…What’s a sink?

7 Plant Nutrition

8 Physiological adaptation
Dogs pee on trees…Why don’t trees pee on dogs? NH3 plant nutrient animal waste

9 Nutritional needs Autotrophic does not mean autonomous plants need…
sun as an energy source inorganic compounds as raw materials water (H2O) CO2 minerals

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

11 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

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

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

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

15 Importance of organic matter
So don’t rake your lawn or bag your leaves Topsoil most important to plant growth 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

16 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

17 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

18 What are the political, economic, environmental issues?
Fertilizers “Organic” fertilizers manure, compost, fishmeal “Chemical” fertilizers commercially manufactured N-P-K (ex ) 15% nitrogen 10% phosphorus 5% potassium What are the political, economic, environmental issues?

19 What will the plant use N for?
Nitrogen uptake Nitrates plants can only take up nitrate (NO3-) Nitrogen cycle by bacteria trace path of nitrogen fixation! root What will the plant use N for?

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

21 Increasing soil fertility
Plow it under? Why would you that? Increasing soil fertility Cover crops 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 A farmer… outstanding in his field? erosion control, too

22 Some plant oddities…

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

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

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

26 Pitcher plant

27 Uses of peat


Download ppt "Transport in Plants 2006-2007."

Similar presentations


Ads by Google