Plant Structure, biology 9.01 Lab help

Lab: Plant Structure

The goal of this lab is to learn about and be able to recognize the various types of cells that occur in a flowering plant.

Introduction:

A plant has two organ systems: 1) the shoot system, and 2) the root system. The shoot system is above ground and includes the organs such as leaves, buds, stems, flowers (if the plant has any), and fruits (if the plant has any). The root system includes those parts of the plant below ground, such as the roots, tubers, and rhizomes.

Angiosperms (“flowering plants”) can be divided into two groups, the monocots and the dicots, on the basis of several diagnostic characteristics.

Rollover the circles to reveal the name of the different parts of the diagram.

LEAVES:

Leaves are the plant organs where most photosynthesis occurs. Their broad flattened structure optimizes the surface area exposed to light. Plant morphologists have developed a hypothesis, supported by scientific evidence, that leaves are flattened stems between which tissue has developed.

The leaf consists of the (generally) flat blade, one or more leaf veins, a petiole, and usually an axillary bud. The petiole can be long (as in celery, rhubarb, and bok-choi) or short (as in cabbage, Brussel’s sprouts, and lettuce). Leaves may be simple or compound: simple leaves have a single subdivision or leaflet, compound leaves have more than one leaflet. Leaves attach to stems at nodes (internodes are the spaces between nodes). Leaf phyllotaxy is the pattern exhibited (spiral, opposite, alternate, whorled) of leaf attachment to a stem.

Table 1. Comparison of monocot and dicot characteristics

Characteristic Monocot Dicot
Leaf vein pattern Parallel Branched
Flower parts Multiple of 3 Multiples of 4 or 5
Cotyledons in the seed One cotyledon (“mono” = one) Two cotyledon (“di” = two)
Vascular bundles in stem x.s. Scattered Circular

u8_lab_flowers.jpg

u8_lab_leaves.jpg

u8_lab_vascularbundles.jpg

u8_lab_embryo.jpg

The outer covering, on both the upper and lower surfaces of the leaf, is the cuticle, a waxy layer that helps lower water loss from the leaf. Openings in the cuticle are the stomata, which are flanked by and regulated by bean-shaped guard cells. Below the upper cuticle is a layer of closely packed cells known as the epidermis. Usually the stomata are located on the lower epidermis. Sandwiched between the leaf is a layer known as the mesophyll (literally, middle leaf).Materials are delivered to and removed from the leaf by a leaf vein.

u8_lab_bundlesheath.jpg

Diagram of a leaf.

Objectives:

  1. To familiarize yourself with the concepts of cells, tissues, organs, and organs systems, and how those relate to the multicellular organism.
  2. To learn about and be able to recognize the various types of cells that occur in a flowering plant.

Time Requirements:

This lab should take two to three hours to complete.

Recording Your Observations:

Click here to download the lab report for this lab.

 
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