# Chapter 35

## Introduction to Plants

### Kingdom Plantae

- We will primarily be discussing the angiosperms 
    - Phylum Anthophyta
- Flowers and fruits 
    - Only group that does/has these things
- Advanced traits 
    - Seeds
    - Advanced vascular tissues

### From seed to seed

#### The life of a flowering plant

- Seeds 
    - reproductive structures produced by angiosperms and other seed plants
    - usually the result of sexual reproduction
    - contains embryos that develop into seedlings upon germination
    - has survival value

#### Alternation of Generations

- Exhibited by all plants (and plant-like organisms) that have sexual reproduction
- There is an alternation between a diploid (2N) form \[sporophyte\] and a haploid (1N) form \[gametophyte\]

##### Gametophyte (haploid)

- Gamete-producing plant fomr
- multicellular
- microscopic in flowering plants 
    - female 
        - embryo sac with egg
    - male 
        - pollen grain
- grow and develop within flowers of angiosperms
- produces gametes by mitosis/cytokineses

##### Sporophyte (diploid)

- multicellular
- large "plant" in flowring plant
- produces haploid spores by meiosis (reduction) 
    - called meiospores

[![Screenshot-from-2019-02-26-15-58-38.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/EWmCJ9pSt3l2cWKw-Screenshot-from-2019-02-26-15-58-38.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/EWmCJ9pSt3l2cWKw-Screenshot-from-2019-02-26-15-58-38.png)

[![Screenshot-from-2019-02-26-16-00-28.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/H2QiK957RFY8COlF-Screenshot-from-2019-02-26-16-00-28.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/H2QiK957RFY8COlF-Screenshot-from-2019-02-26-16-00-28.png)

## The plant embryo

- Fertilization (syngamy) results in the formation of a diploid zygote, which undergoes mitosis to form an embryo (multicellular)
- the embryo is a sporophyte that lies dormant in the seed with a supply of stored food and a seed coat
- may lay dormant for long periods until conditions are favorable

## The plant body

Composed of three organ types

- stems
- leaves
- roots

### Shoot system

- stem 
    - produce leaves and branches and bear the reproductive structures
- leaves 
    - flattened structure specialized for photosynthesis

### Root system

- roots 
    - Provide anchorage in the soil and foster efficient uptake of water and minerals
    - can store food

## Growth

- Indeterminate growth 
    - increasing in size as long as the plant is alive
- grows into a seedling and then a mature plant
- Plant growth occurs by 3 means 
    - Increase in number of cells 
        - cellular reproduction 
            - (mitosis/cytokineses)
    - increase in cell size 
        - elongation
    - increase in weight/mass

### Development

- Mature plants produce reproductive structures 
    - flowers
    - seeds
    - fruits
- flowers and floral buds are reproductive shoots that develop when shoot apical (tip) meristems produce flower parts instead of new tissues and leaves
- flowers are produced by determinate growth

### Seed coats

- Flower tissues enclose and protect tiny male and female gametophytes 
    - sperm in pollen fertilizes the egg, triggering ovules to develop into seed and flower parts to develop into fruit
- fruits enclose seeds and function in seed dispersal 
    - Angiosperms

[![Screenshot-from-2019-02-26-17-00-05.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/fGG0vidbb24sxcwx-Screenshot-from-2019-02-26-17-00-05.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/fGG0vidbb24sxcwx-Screenshot-from-2019-02-26-17-00-05.png)

### Meristems

- Seedlings and mature plants produce new tissue from meristems 
    - cell factories
- meristem is a region of undifferentiated cells that produce new tissue by cell division
- A dormant meristem occurs at the shoot and root of seed embryos 
    - activate in seedlings
- mature plants have shoot apical meristems (SAM) and root apical meristems (RAM)

### Mature sporophyte develop from seedlings

- photosynthesis powers the transformation of seedlings into mature plants
- provides the ability to produce organic food
- plants undergo both vegetative growth and reproductive development

#### Hierarchy of structures in a mature plant

- Specialized cells
- tissues
- organs
- organ systems 
    - branches, buds, flowers, seeds, fruits
- root and shoot systems
- plant (the organism itself)

### Primary Growth

- Elongation of plant organs
- roots, stems, and leaves
- Occurs in ALL plants
- Produces primary tissues from apical meristems (SAM and RAM)

#### Primary Tissues

- Primary xylem 
    - vascular/conducting tissue
    - water and minerals
- Primary phloem 
    - vascular/conducting tissue
    - food and solutes
- Epidermis 
    - dermal 
        - Outter-most tissue
    - protection
    - holds water in plant
- Support ground tissues 
    - Parenchyma 
        - most abundant type
        - storage 
            - water and food
        - part of cortex/pith
    - Collenchyma 
        - Protection/support of growing plant organs
        - cortex
    - Sclerenchyma 
        - protection/support of non-elongating organs
        - cortex

### Secondary Growth

- Expansion of plant organs 
    - lateral meristems
- roots and stems only 
    - does not occur in leaves
- noes not occur in all plants
- Produces secondary tissues 
    - woody tissues

## Major groups of Angiosperms

### Eudicots

- >240,000 species
- all have primary growth
- most have secondary growth 
    - for this class we are saying they all have secondary growth

### Monocots

- >60,000 species
- all have primary growth
- very few have secondary growth 
    - for this class we are saying that non have secondary growth
- grasses, corn, tulips, lilies

## Root system adaptations

### Major functions

- absorbing water and minerals
- anchoring the plant in the soil
- storing nutrients and water

#### Eudicots

Taproots

[![Screenshot-from-2019-02-26-18-53-37.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/J7qi1b81Z7bgWQhy-Screenshot-from-2019-02-26-18-53-37.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/J7qi1b81Z7bgWQhy-Screenshot-from-2019-02-26-18-53-37.png)

#### Monocots

fibrous roots

[![Screenshot-from-2019-02-26-18-53-45.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/2lu7qXPIFEybIUXS-Screenshot-from-2019-02-26-18-53-45.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/2lu7qXPIFEybIUXS-Screenshot-from-2019-02-26-18-53-45.png)

### Three zones of root growth

1. Region of cell division 
    - RAM and root cap
    - RAM contains cells that ar dividing
    - Quiescent center keeps nearby cells undifferentiated
    - Root cap embedded in mucigel 
        - Mucigel is a slimy substance that covers the root cap of the roots of plants.
2. Region of elongation 
    - cells extend by uptake of water
3. Region of maturation 
    - root cell differentiation and tissue specialization
    - identified by presence of root hair 
        - water and mineral uptake

[![Screenshot-from-2019-02-26-19-00-06.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/9uQ5eibWqgokbDIc-Screenshot-from-2019-02-26-19-00-06.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/9uQ5eibWqgokbDIc-Screenshot-from-2019-02-26-19-00-06.png)

### Root Internal Structure

- Epidermis of mature roots encloses a cylinder of parenchyma called the root cortex 
    - One cell thick
    - often rich in starch 
        - functions as food storage
    - many contain inter-cellular air spaces
- Endodermis 
    - selective absorption of minerals
    - one cell thick
- Meristematic pericycle 
    - encloses root in vascular tissues
    - provides lateral branches
- woody roots produce primary vascular tissues followed by secondary vascular tissues

#### Eudicot root

[![gb110629_young_dicot_root400.jpg](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/2ABWpCGikmznHja3-gb110629_young_dicot_root400.jpg)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/2ABWpCGikmznHja3-gb110629_young_dicot_root400.jpg)

#### Monocot Root

[![plant-organ-cross-sections-4-638.jpg](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/rUIaZuaDhTDXLzI3-plant-organ-cross-sections-4-638.jpg)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/rUIaZuaDhTDXLzI3-plant-organ-cross-sections-4-638.jpg)

## The shoot system

Stem and leaf adaptations

Shoots are modular with 4 parts

1. Stem node 
    - leaves or branches emerge
2. Internode 
    - stem between adjacent nodes
    - elongation
3. Leaf
4. Axillary Meristem 
    - generate axillary buds
    - can produce flowers or branches 
        - Lateral shoots
    - New branches bear SAM at their tips

### Shoot Tip

- Terminal bud 
    - at the end of each shoot
    - includes the SAM and other parts
    - scales

[![Screenshot-from-2019-02-26-20-15-41.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/L6PebciohUi8GIl5-Screenshot-from-2019-02-26-20-15-41.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/L6PebciohUi8GIl5-Screenshot-from-2019-02-26-20-15-41.png)

### Leaf anatomy

[![schematic_gas_exchange_across.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/Sn4bFqEygOIzvHXk-schematic_gas_exchange_across.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/Sn4bFqEygOIzvHXk-schematic_gas_exchange_across.png)

#### Leaf adaptation

##### Leaf venation

Eudicot

- Pinate (feathery)
- Palmate (palm)
- Netted 
    - provides more support for the leaves

Monocot

- Parallel

### Stem

#### Primary growth

- mostly above ground organs,but some modified stems are blow ground 
    - Irish potato 
        - underground stem

#### Eudicot Stem

- ALC
- Primary (elongation) and secondary (expansion) growth
- vascular bundles (xylem and phloem) form a ring pattern
- exhibit both a pith and a cortex
- cambium ring produce cells 
    - provide secondary growth

[![(11).PNG](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/HD9w6L6LSUgsvanp-(11).PNG)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/HD9w6L6LSUgsvanp-(11).PNG)

##### Lateral Meristems

- Produces secondary growth
- 2 lateral merstems 
    - both are rings that retain cell division properties and produce secondary tissues to the inside and outside of the cambium ring
- Vascular cambium 
    - produces ring of **secondary xylem (wood)** to the inside and a ring of **secondary phloem (inner bark)** to the outside
- Cork cambium 
    - Produces ring of **periderm (outter bark)** that replaces the epidermis and cortex for external protection

[![Screenshot-from-2019-02-26-21-35-35.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/9mGGBwHzFRK33oAq-Screenshot-from-2019-02-26-21-35-35.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/9mGGBwHzFRK33oAq-Screenshot-from-2019-02-26-21-35-35.png)

- Secondary vascular tissue 
    - woody plants begin life with only primary vascular systems 
        - produces secondary tissues and bark as they mature
    - secondary xylem 
        - wood
    - Secondary phloem 
        - inner part
    - bark has both outer bark (mostly dead cork cells) and inner bark (secondary phloem)
- Secondary growth 
    - begins late in first year of growth
    - eudicot stem after 3 years of growth

[![Screenshot-from-2019-02-26-21-41-28.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/CpDkR3lV9BHcnMHG-Screenshot-from-2019-02-26-21-41-28.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/CpDkR3lV9BHcnMHG-Screenshot-from-2019-02-26-21-41-28.png)

#### Monocot stem

- Primary growth (elongation)
- vascular bundles (xylem and phloem) are scattered
- lacks both pith and cortex

[![191e446a2dca02705221bbb36e44e7d3.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/UEbbkStBxBtSJZAZ-191e446a2dca02705221bbb36e44e7d3.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/UEbbkStBxBtSJZAZ-191e446a2dca02705221bbb36e44e7d3.png)

## Comparison between Plant types

### Leaves

#### Eudicot

- net venation

#### Monocot

- parallel venation

### Roots

#### Eudicot

- primary and secondary growth (mostly)
- cortex
- no pith
- core of xylem in the root

#### Monocot

- Primary growth only
- both cortex and pith

### Stems

#### Eudicot

- primary and secondary growth (mostly)
- vascular bundles in a ring pattern around cortex

#### Monocot

- Primary growth only
- vascular bundles scattered around
- no pith or cortex

## Primary Growth

- Due to activities of Apical Meristems 
    - RAM and SAM
- Results in production of primary growth

## Secondary Growth

- Due to activities of lateral maristems 
    - vascular and cork cambiums
- Results in production of secondary tissues

[![Screenshot-from-2019-02-26-21-58-07.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/RFbBiylaTovAHBWJ-Screenshot-from-2019-02-26-21-58-07.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/RFbBiylaTovAHBWJ-Screenshot-from-2019-02-26-21-58-07.png)[![Screenshot-from-2019-02-26-21-57-55.png](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/scaled-840-0/ww8tDI312NbYEzpI-Screenshot-from-2019-02-26-21-57-55.png)](https://bookstack.aronwk.com/uploads/images/gallery/2019-02-Feb/ww8tDI312NbYEzpI-Screenshot-from-2019-02-26-21-57-55.png)