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Plant Organs and Transport

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Presentation on theme: "Plant Organs and Transport"— Presentation transcript:

1 Plant Organs and Transport
Sections 13.3 – 13.4

2 Learning Goal To learn more about the details of plant organs and their functions To better understand how water and nutrients move in and out of plant cells

3 Introduction – Review Parts of Plant cell

4 Roots Root system is usually the 1st structure to grow from a seed when it sprouts Roots have 3 Main Functions: Take in water and dissolve minerals that are transported to where needed in the rest of the plant Anchor the plant in the soil to support the plant against forces like wind and water Store the carbohydrates that are produced by photosynthesis in the leaves or green stems, as well as water and other nutrients

5 Root Structure and Function
The tip of the root is covered by the Root Cap The Root Cap is made up of parenchyma cells that help protect the growing tissues as the root extends through soil or more resistant materials, like rocks

6 Root Structure and Function
The roots apical meristem produces new cells that develop into different types of root tissues that have different functions Example- some replace lost cells due to friction, while others grow and increase the length of the root

7 Outer Root Layers Like the rest of the plant, the root is covered in a layer of Dermal Tissue Epidermal cells produce root hairs that increase the surface area of the root This increases the area where the root is able to absorb water and dissolve mineral

8 Outer Root Layers Just inside the epidermis is the Cortex
The cortex lies between the epidermis and the vascular tissue of the root This layer is made up of ground tissue (made of parenchyma cells) that transport and store water, food, and minerals All materials that enter the root pass through the cortex to get to the vascular tissue, to the rest of the plant

9 Outer Root Layers On the inside edge of the cortex, between the cortex and the vascular tissue is called the layer called the Endodermis This is one THICK cell that is surrounded by a waterproof band called a Casparian strip Forces water and minerals to cross the plasma membrane through the cytoplasm So that the endodermal cells control only water and certain nutrients to enter the vascular system

10 Outer Root Layers

11 Inner Root Vascular Tissue
Inside the endodermis are the vascular tissues, xylem and phloem = together they make up the Centre of the Root The arrangement of xylem and phloem is different in monocot and dicot flowering plants

12 Types of Root Systems There are 2 main types of roots: Taproot
Fibrous Roots Made of THICK root system with smaller lateral branching roots Anchors plants Absorb water and minerals Stores food and water below ground level Ex- Carrots , dandelions Made up of smaller branching roots Roots are about the same size that grow from a central point Don’t grow as deep as taproots Ex – grass roots, scallions

13 Types of Root Systems

14 Stems There many different types of stems, who’s function is to provide support for the plant’s leaves and reproductive structures Based on various adaptations, stems can be soft and flexible or hard and woody in order to help plants survive

15 Types of Stems Stems are used to store excess food, while others help the plant withstand drought, cold, or heat There are 5 different types of stems: Type of Stem Description / Example Tuber Like the potato – is an enlarged part of an underground stem Bulb Like the onion – are shortened, compress stems surrounded by fleshy leaves Corms Like crocuses – made up of stem tissue with some scaly leaves at its top Stolons Like strawberries – have horizontal stems that grow above ground along the top Rhizomes Like Irises – have horizontal stems that grow underground

16 Leaf Structure and Function
Regardless of the different shape or size of leaves, they all have the same function: to convert light energy from the Sun into chemical energy for food via photosynthesis

17 Leaf Structure and Function
The external structure of a typical leaf has a flat portion called the blade The blade and the stem can attach directly or indirectly through a structure called a petiole The epidermal cells of leaves release a waxy substance that forms the cuticle Acts as a protective layer that keeps water in and reduce evaporation Vascular tissue runs through the petiole, connecting the leaf, veins, and stem to transport vital nutrients throughout

18 Internal Structure of a Leaf

19 Internal Structure of a Leaf
The cuticle and the epidermis of a leaf are transparent, which lets light through it Between the upper and lower epidermis of a leaf is the mesophyll Right below the upper epidermis is a row of tightly packed cells celled the palisade mesophyll cells They contain lots of chloroplast, which is why most photosynthesis takes place here

20 Internal Structure of a Leaf
Below the palisade mesophyll is the spongy mesophyll The cells located here are irregular in shape and loosely packed to allow for gas exchange to take place, where: Reactants CO2 + H2O move in Waste Product O2 moves out

21 Identifying Leaves Ventilation: the pattern of veins in a leaf

22 Flowering Plants: Mono vs. Dicots
Flowering plants can be classified as monocots or dicots based on the number of seed leaves in their embryos, where If they have 1 seed in their embryo = monocot If they have 2 seeds in their embryo = dicots

23

24 Transportation in Plants
Section 13.4

25 Introduction Vascular plants have a conducting system to transport fluids and nutrients from 1 part of the plant to another Basically – a plant is a tube with its base embedded in the ground, where the base of the tube is the root system, and the leaves are at the top of the tube

26 Introduction A plant needs 2 kinds of transportation
Job One – move sugars Sugars made in the leaves by photosynthesis must be carried to all other living cells in the plant So WATER that carries these dissolved sugars must move up and down the tube Cells in the Phloem do this Job Two – move water up Water and dissolved nutrients must be taken up by the roots and sent to cells, so water moves up the tube Cells in the Xylem do this

27 How things move in / out Particles move based on concentration gradients – the amount of a substance on one side versus the other This movement is called DIFFUSION Where substances move from a HIGH concentration to a LOW concentration

28 How things move in / out Similarly, water also moves from a HIGH [ ] to a LOW [ ] This more specific type of diffusion is called OSMOSIS Diffusion and Osmosis occur naturally and allow water, sugars, and nutrients to be transported throughout the plant

29 How things move in / out However, minerals like nitrates found in abundance in the soil are needed by the plants in small amounts Diffusion would not work in this case Instead plants use Active Transport to intake such minerals from a LOW concentration to a HIGH concentration

30 Transport in the Xylem The root cells have a higher [ ] of dissolved nutrients than the surrounding soil So water moves INTO the roots by Osmosis, where: Water moves through the root cells or intercellular spaces within the root and enters the Xylem The water is then transported in the Xylem up through the root into the stem Inside the stem, water moves by Osmosis into other tissues Most minerals from the soil move via Active Transport

31 Transport in the Xylem As the xylem tissue carrying water and minerals enters the leaf, the conducting vessels branch into the many veins From the end of each vein, water and minerals can diffuse into the cells of the leaf Unfortunately, more than 90% of the water that reaches the leaf evaporates out through the stomata through a process called transpiration

32 Transport in the Xylem

33 Transport in the Xylem Long distance transport in the Xylem is done by 2 processes: Root pressure & Transitional pull Root Pressure – where positive pressure (pushing)work with Transitional Pull – the negative pressure (pulling) help move water move up through the xylem

34 Transport in the Xylem Root Pressure
Recall – is the mechanism that pushes water and minerals upwards in a plant Water entering the roots create a POSITIVE Pressure that pushes water UP Minerals move from the soil into the xylem against their [ ] gradients by Active Transport The now added minerals in the xylem makes MORE water move up by OSMOSIS This process is added by the adhesion (sticking) of water molecules to the cell walls of the xylem tissue

35 Transport in the Xylem Root Pressure
In shorter plants, root pressure can be seen as water droplets on leaves called guttation This occurs under High Humidity – where water can’t evaporate from these leaves and the rate of Transpiration is low

36 Transport in the Xylem Transpirational Pull
Looks at pulling water up AGAINST Gravity Negative pressure (Pulling) from above is the Strongest force for long-distance heights The COHESION-TENSION MODEL accounts for the majority of water and minerals moving from the roots all the way up in the leaves of the tallest trees Since more than 90% of water that is absorbed from the roots is lost via Transpiration, water from the leaves creates a negative pressure that PULLS water up to replace its loss in evaporation

37 Transport in the Xylem Transpirational Pull
There are 3 Main Factors that are vital to this model: Transpiration – the evaporation of water molecules from the shoot system, is responsible for the movement of water and dissolved minerals upward in a plant stem. Dry air, heat, and wind cause this to take place, as water exits through the stomata

38 Transport in the Xylem Transpirational Pull
Cohesion – the columns of water in the xylem have a property called cohesion, where the force of attraction between water molecules keeps them together in the xylem

39 Transport in the Xylem Transpirational Pull
Adhesion – causes the water molecules to stick to the xylem walls. Adhesion works with cohesion to keep water from separating and keeps on being pulled up in the plant

40 Transport in the Xylem

41 Movement of water

42 VIDEO:

43 Nutrient Transport in Phloem
Photosynthesis occurs in the green parts of the plant, where sugars like glucose and sucrose are made as food for the plant Translocation is the way in which these sugars get moved throughout the plant to areas that are needed through the phloem

44 Translocation: Pressure Flow Model
Translocation in the phloem moves sucrose from a source from any part of the plant that enter into a sieve tube (like palisade and spongy mesophyll tissues in the leaf) and into a SINK

45 Translocation: Pressure Flow Model
The SINK is any region in the plant where sugars are used or stored For example – while flowers and fruits of a plant are developing, they are also sinks because they need organic molecules to grow Roots are also sinks because they need nutrients to grow, and because they also store carbohydrates during the winter

46 Translocation: Pressure Flow Model
Water and minerals are mostly pulled up by translocation Nutrients are pushed through the phloem The Pressure-Flow Model believes plants use a combination of osmosis and pressure dynamics to explain how materials are pushed from a source to a sink via translocation Video:

47 Translocation: Pressure Flow Model
Read pg. 564 to explain how the glass bulb analogy relates to this model

48 Translocation

49 Pressure Flow in Phloem
When nutrients are pumped into or removed from the phloem, the changes in concentration causes a movement of water in that same direction Thus, the internal pressure builds up at the source end of the sieve tube and pushes the sucrose-rich solution toward any sink, where the sucrose is then removed

50

51 Pressure Flow in Phloem
RECALL: In the xylem, it is mostly negative pressure moving water and dissolved minerals In the phloem, its positive pressure that moves the flow of sucrose from the source into the sink

52 Pressure Flow in Phloem
The direction of flow is always from source to sink, and the sinks change depending on the plant’s stage of growth and development Ex – in older plants, the newly synthesized leaves are a sink , and the sucrose moves there from photosynthesizing leaves to growing leaves When fruit is forming, sucrose moves there by translocation, and growth in other areas of the plant slows down

53

54 Plant Transpiration LAB - http://www. mhhe


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