Examine the shoot system of a mature plant. Identify the shoot tip, nodes, internodes, leaves, and axillary buds. Note that axillary buds always occur above a leaf. Axillary buds give rise to branch shoots. Thus, branching in a shoot system is exogenous (of external origin). How does this compare to branching in a root system?
1. Examine the shoot system of a mature plant. Identify the shoot tip, nodes, internodes,
leaves, and axillary buds. Note that axillary buds always occur above a leaf. Axillary buds give
rise to branch shoots. Thus, branching in a shoot system is exogenous (of external origin).
How does this compare to branching in a root system?
2. Examine a longitudinal section through a Coleus stem tip. Identify the apical meristem, leaf
primordia (developing leaf), bud primordia (developing axillary buds), nodes, and internodes.
Beginning with the apical meristem, follow the development of shoot tissues. Identify protoderm, procambium, and ground meristem, pith, and cortex.
A) You will not be able to identify any mature cells or tissues in this slide (keep in mind the
size of the
shoot tip). What are the mature tissues that each of these primary meristems become?
B) Can you find a node (where procambium diverges in to the leaf primordium)? These areas
are also commonly called Aleaf gaps@. However, because seed plants have eusteles instead
of siphonosteles they are not the same as leaf gaps in ferns. Do you understand the
differences? If not, ask.
3. Examine mature plants on demonstration. Marks were made at regular intervals along the
length of the stem. Based on the present distances between marks, which part of the stem
elongated?
4. Examine a transverse section through a
vascular bundles. Note that the vascular bundles do not form a single, discrete ring. Identify
the bundle sheaths, composed of fibers, that surround each vascular bundle. Now identify the
sieve tube members and companion cells of the primary phloem, and the vessel members of
the proto- and metaxylem (primary xylem).
5. Examine a transverse section through a
cortex, pith, and vascular bundles. Within a vascular bundle, identify the phleom, phloem fibers,
primary xylem, and procambium. Note that the procambium forms a complete ring throughout
the stem. Procambium within a vascular bundle separates the primary xylem and phloem, and
is therefore called intrafasicular ("within a fasicle) procambium, whereas procambium between
bundles is called interfasicular ("between fasicles") procambium. The regions between the
vascular bundles, composed of parenchyma and interfasicular procambium are called pith rays.
Did the Zea (monocot) stem possess residual procambiu
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