Download Objectives: 1. Investigation of Angiosperms (flowering plants) and

Lab 11: Plant Pigments and Photosynthesis
Visit the link below and complete the exercises. The following information is meant to
enhance your understanding.
http://www.phschool.com/science/biology_place/labbench/lab4/intro.html
Objectives:
1. Investigation of Angiosperms (flowering plants) and
evaluate the differences between monocots and dicots.
2. Become familiar with external and internal plant structure.
3. Analyze important structural features.
4. Consider variations in plant structures, offer hypotheses as
to the function of these adaptations.
Introduction:
Most people think of plants as “uninteresting” because they can’t catch
a ball or purr. However, plants have incredibly diverse forms and are
frequently grown and photographed for their economic, medicinal and
aesthetic properties. The use of plants in promoting human health has
been practiced for centuries. While you may not fully appreciate
plants, at the conclusion of today’s laboratory, it is hoped that at the
very least you will have gained insight and experience into the world of
plants and their importance and diversity.
Plants include green algae, mosses and liverworts, ferns, gymnosperms
and angiosperms. Our focus will be on angiosperms. The angiosperm
(vascular, flowering plants) body includes three basic organs: roots,
stems and leaves each reflecting their basic function of the plant.
These organs are products of growth regions called meristems and are
areas that retain the capability of cell division. The roots have a high
surface area as a result of numerous root hairs, an adaptation that
facilitates the absorption of water. The typical stem has evolved in
order to support its leaves in a manner that maximizes exposure to
sunlight. Leaves are typically wide and flat and represent features
increased surface area, and adaptation that allows the capture of
sunlight by photosynthetic tissues that produce food. All of these
structures are interconnected by vascular tissue, which transports
material throughout the entire plant.
Roots have four main functions: 1.) Anchor the plant in soil, 2.)
Absorption of water and minerals from the soil, 3.) Transport of water
and minerals to the shoot system, absorption occurs through root hairs
which are extensions of root epidermal cells, 4.) Food storage for the
plants in the cortex of many taproots. There are two major types of
roots. Taproots have one large main root with shorter, thinner branch
roots that branch from its side. Fibrous roots have multiple roots of
similar size.
Stems have four main functions: 1.) support, accomplished through
turgor pressure (water pressure in cells), thick cell walls, and fibers that
resist breaking. In addition, the center portion of most stems has
varying amounts of pith, which is ground tissue of large parenchyma
cells, 2.) transport of substances between roots and leaves by vascular
tissue of two types- xylem and phloem, 3.) green stems produce food
by photosynthesis, 4.) storage of food and water.
Leaves are the chief food-producing organs in most plants. Diffusion of
respiratory and photosynthetic gases in and out of the plant occurs
through stomata on the surface of the leaf. Other than the stomata, a
waterproof cuticle covers the leaf and prevents excessive water loss.
Guard cells surrounding the stomata open and close according to the
plants internal characteristics. Most of the leaf interior consists of
palisade and spongy mesophyll, which is composed of photosynthetic
cells that produce many organic compounds. Air spaces throughout the
spongy mesophyll are continuous with the stomata to the leaf exterior
and thus facilitate gas exchange.
Primary growth occurs as an increase in shoot and root length due to
primary (apical) meristem cells. Roots reach deeper into the soil by
primary growth. A root cap protects the dividing meristem tip from
abrasion. Behind the meristem new cells increase the length and
actually push the root tip through the soil. Behind this area is where
cells reach full size and become specialized for specific functions. One
such example is the endodermis, which controls the movement of
substances between the root cortex and root interior.
Stems increase in length as the apical meristems produce new cells.
Secondary growth increases the stem girth is produced by the vascular
cambium, a ring of secondary (lateral) meristem that gives rise to
secondary xylem (wood). The stem grows in diameter as new xylem
cells are produced toward the stem interior. The pholemoutside the
vascular cambium is crushed as stem diameter increases. Destroyed
phloem is replaced by secondary phloem that is produced by cells on
the opposite side of the vascular cambium. As more wood is produced,
more secondary phloem is destroyed but again is replaced. The process
continues and the stem grows even wider. The cork cambium (another
secondary meristem) is located on the outside of the secondary
phloem. It produces a protective waterproof layer of cork. Secondary
phloem and cork layer compose the tree bark.
Branches are produced by different processes in roots and stems.
Branch roots arise from the meristematic pericycle within the root
interior. The branch roots grow through the cortex and emerge into
the soil. Stem branches occur as auxiliary (lateral ) buds become
mitotically active producing new shoots.
Angioperms are usually divided into two broad groups: Monocots
(typically producing a single cotyledon, a modified leaf found in each
seed) and Dicots (typically producing two cotyledons in each seed). In
addition, a number of other traits distinguish the monocots and dicots.
See Table 1. Moncots are usually herbaceous with few trees and no
significant secondary growth, while dicots occur as herbs, shrubs and
trees sometimes with impressive amounts of secondary growth.
Table1.
Monocot
Dicot
Dicots tend to produce taproots while monocots have fibrous root
systems.
In today’s lab you will investigate examples of angiosperms beginning
with a consideration of external structures, followed by examination of
internal structures. You will consider adaptations plants have made to
particular environmental conditions.