1. Chapter 35 Plant Structure, Growth and Developoment

2. Concept 35.1: Plants have a hierarchical organization consisting of organs, tissues, and cells
Plants have organs composed of different tissues, which in turn are composed of different cell types
A tissue is a group of cells consisting of one or more cell types that together perform a specialized function
An organ consists of several types of tissues that together carry out particular functions

3. The Three Basic Plant Organs: Roots, Stems, and Leaves
Basic morphology of vascular plants reflects their evolution as organisms that draw nutrients from below ground and above ground
Plants take up water and minerals from below ground
Plants take up CO2 and light from above ground

4. Three basic organs involved: roots, stems, and leaves
They are organized into a root system and a shoot system

5. Reproductive shoot (flower)
Figure 35.2
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical bud
Shoot system
Vegetative shoot
Axillary bud
Blade
Leaf
Petiole
Stem
Figure 35.2 An overview of a flowering plant.
Taproot
Root system
Lateral (branch) roots

6. Roots rely on sugar produced by photosynthesis in the shoot system, and shoots rely on water and minerals absorbed by the root system
Monocots and eudicots are the two major groups of angiosperms

7. Roots A root is an organ with important functions: Anchoring the plant
Absorbing minerals and water
Storing carbohydrates (as in Medicago sativa)

8. Most monocots have a fibrous root system, which consists of:
Most eudicots and gymnosperms have a taproot system, which consists of:
A taproot, the main vertical root
Lateral roots, or branch roots, that arise from the taproot
Most monocots have a fibrous root system, which consists of:
Adventitious roots that arise from stems
Lateral roots that arise from the adventitious roots

9. In most plants, absorption of water and minerals occurs near the root hairs, where vast numbers of tiny root hairs increase the surface area

10. Stems A stem is an organ consisting of
An alternating system of nodes, the points at which leaves are attached
Internodes, the stem segments between nodes

11. An axillary bud is a structure that has the potential to form a lateral shoot, or branch
An apical bud, or terminal bud, is located near the shoot tip and causes elongation of a young shoot
Apical dominance helps to maintain dormancy in most axillary buds

12. Many plants have modified stems (e. g
Many plants have modified stems (e.g., rhizomes, bulbs, stolons, tubers)

13. Rhizomes Rhizome Root Bulbs Storage leaves Stem Stolons Stolon Tubers
Figure 35.5
Rhizomes
Rhizome
Root
Bulbs
Storage leaves
Stem
Stolons
Stolon
Figure 35.5 Evolutionary adaptations of stems.
Tubers

14. Leaves
The leaf is the main photosynthetic organ of most vascular plants
Leaves generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem
© 2011 Pearson Education, Inc.

15. Monocots and eudicots differ in the arrangement of veins, the vascular tissue of leaves
Most monocots have parallel veins
Most eudicots have branching veins
In classifying angiosperms, taxonomists may use leaf morphology as a criterion

16. Simple leaf Axillary bud Petiole Compound leaf Doubly compound leaf
Figure 35.6
Simple leaf
Axillary bud
Petiole
Compound leaf
Doubly compound leaf
Leaflet
Figure 35.6 Simple versus compound leaves.
Petiole
Axillary bud
Axillary bud
Petiole
Leaflet

17. The vascular tissue system carries out long-distance transport of materials between roots and shoots
The two vascular tissues are xylem and phloem
Xylem conveys water and dissolved minerals upward from roots into the shoots
Phloem transports organic nutrients from where they are made to where they are needed

18. The vascular tissue of a stem or root is collectively called the stele
In angiosperms the stele of the root is a solid central vascular cylinder
The stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem

19. Concept 35.2: Meristems generate cells for primary and secondary growth
A plant can grow throughout its life; this is called indeterminate growth
Some plant organs cease to grow at a certain size; this is called determinate growth

20. Meristems are perpetually embryonic tissue and allow for indeterminate growth
Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots
Apical meristems elongate shoots and roots, a process called primary growth

21. Lateral meristems add thickness to woody plants, a process called secondary growth
There are two lateral meristems: the vascular cambium and the cork cambium
The vascular cambium adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
The cork cambium replaces the epidermis with periderm, which is thicker and tougher

22. Primary growth in stems
Figure 35.11
Primary growth in stems
Epidermis
Cortex
Primary phloem
Shoot tip (shoot apical meristem and young leaves)
Primary xylem
Pith
Vascular cambium
Secondary growth in stems
Cork cambium
Lateral meristems
Cork cambium
Axillary bud meristem
Cortex
Periderm
Primary phloem
Figure An overview of primary and secondary growth.
Pith
Secondary phloem
Root apical meristems
Primary xylem
Vascular cambium
Secondary xylem

23. Flowering plants can be categorized based on the length of their life cycle
Annuals complete their life cycle in a year or less
Biennials require two growing seasons
Perennials live for many years

24. Concept 35.3: Primary growth lengthens roots and shoots
Primary growth produces the parts of the root and shoot systems produced by apical meristems

25. Primary Growth of Roots
The root tip is covered by a root cap, which protects the apical meristem as the root pushes through soil
Growth occurs just behind the root tip, in three zones of cells:
Zone of cell division
Zone of elongation
Zone of differentiation, or maturation

26. Zone of differentiation Ground Root hair Vascular
Figure 35.13
Cortex
Vascular cylinder
Key to labels
Epidermis
Dermal
Zone of differentiation
Ground
Root hair
Vascular
Zone of elongation
Figure Primary growth of a root.
Zone of cell division (including apical meristem)
Mitotic cells
100 m
Root cap

27. Core of parenchyma cells
Figure 35.14
Epidermis
Cortex
Endodermis
Vascular cylinder
Pericycle
Core of parenchyma cells
Xylem
100 m
Phloem
100 m
(a)
Root with xylem and phloem in the center (typical of eudicots)
(b)
Root with parenchyma in the center (typical of monocots)
50 m
Key to labels
Figure Organization of primary tissues in young roots.
Endodermis
Pericycle
Dermal
Xylem
Ground
Phloem
Vascular

28. The ground tissue, mostly parenchyma cells, fills the cortex, the region between the vascular cylinder and epidermis
The innermost layer of the cortex is called the endodermis
The endodermis regulates passage of substances from the soil into the vascular cylinder

29. Lateral roots arise from within the pericycle, the outermost cell layer in the vascular cylinder

30. Tissue Organization of Stems
Lateral shoots develop from axillary buds on the stem’s surface
In most eudicots, the vascular tissue consists of vascular bundles arranged in a ring
In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring

31. Sclerenchyma (fiber cells) Ground tissue
Figure 35.17
Phloem
Xylem
Sclerenchyma (fiber cells)
Ground tissue
Ground tissue connecting pith to cortex
Pith
Epidermis
Key to labels
Epidermis
Cortex
Vascular bundles
Figure Organization of primary tissues in young stems.
Vascular bundle
Dermal
1 mm
1 mm
Ground
(a)
Cross section of stem with vascular bundles forming a ring (typical of eudicots)
(b)
Vascular
Cross section of stem with scattered vascular bundles (typical of monocots)

32. Tissue Organization of Leaves
The epidermis in leaves is interrupted by stomata, which allow CO2 and O2 exchange between the air and the photosynthetic cells in a leaf
Each stomatal pore is flanked by two guard cells, which regulate its opening and closing
The ground tissue in a leaf, called mesophyll, is sandwiched between the upper and lower epidermis

33. The mesophyll of eudicots has two layers:
The palisade mesophyll in the upper part of the leaf
The spongy mesophyll in the lower part of the leaf; the loose arrangement allows for gas exchange

34. Cross section of a lilac (Syringa) leaf (LM)
Figure 35.18c
Upper epidermis
Palisade mesophyll
Spongy mesophyll
100 m
Lower epidermis
Guard cells
Figure Leaf anatomy.
Vein
Air spaces
(c)
Cross section of a lilac (Syringa) leaf (LM)

35. The vascular tissue of each leaf is continuous with the vascular tissue of the stem
Veins are the leaf’s vascular bundles and function as the leaf’s skeleton
Each vein in a leaf is enclosed by a protective bundle sheath

36. Concept 35.4: Secondary growth increases the diameter of stems and roots in woody plants
Secondary growth occurs in stems and roots of woody plants but rarely in leaves
The secondary plant body consists of the tissues produced by the vascular cambium and cork cambium
Secondary growth is characteristic of gymnosperms and many eudicots, but not monocots

37. Cross section of a three-year- old Tilia (linden) stem (LM)
Figure 35.19b
Secondary phloem
Bark
Vascular cambium
Cork cambium
Late wood
Secondary xylem
Periderm
Early wood
Cork
0.5 mm
Figure Primary and secondary growth of a woody stem.
Vascular ray
Growth ring
(b)
Cross section of a three-year- old Tilia (linden) stem (LM)
0.5 mm

38. The Vascular Cambium and Secondary Vascular Tissue
The vascular cambium is a cylinder of meristematic cells one cell layer thick
It develops from undifferentiated parenchyma cells

39. After one year of growth After two years of growth
Figure 35.20
Vascular cambium
Growth
Vascular cambium
Secondary phloem
Secondary xylem
Figure Secondary growth produced by the vascular cambium.
After one year of growth
After two years of growth

40. Tree rings are visible where late and early wood meet, and can be used to estimate a tree’s age
Dendrochronology is the analysis of tree ring growth patterns and can be used to study past climate change