Rabbits

Raceme

                    DIAGRAM:  Raceme

                          PHOTO:  

Rachis

The rachis is the main axis of the pinnately compound leaf.  It is the portion of the pinnately compound leaf that is attached to the petiole.

                    DIAGRAM:  Fern Frond

                          PHOTO:  

Radish

Radial

Radial Wall

(casparian strip)

Radial Section

A radial section is a longitudinal section of the stem that follows the radius (diameter) of the stem. It follows and is parallel to a vascular ray.

                    DIAGRAM:  Stem Sections

                          PHOTO:  

Radicle

The radicle  is the structure that will become the root in a mature plant.  When it grows out of the seed and into the soil, it grows downward.

                    DIAGRAM:  Cotyledons / Acorn

                          PHOTO:  Seed Cross Section / Seed Cross Section

Range of Tolerance

Raphe

Raspberry

Ray Flowers

                    DIAGRAM:

                          PHOTO: Composite Flower / Composite Flower / Composite Flower
                                          Composite Flower 

Ray Initial

In the vascular cambium, some cells produce the axial system and other cells produce the radial system of vascular tissue.  Those vascular cambial cells that produce the radial system are known as the ray initials and those vascular cambial cells that produce the axial system are known as the fusiform initials.  The fusiform initials are responsible for forming all the conducting and strengthening cells in the xylem and phloem areas of the stem and root.

Radial System

The radial system is the vascular transport system in a stem that runs horizontally from the center of the stem. This is in contrast to the axial system that runs up and down the stem.  The radial system carries mostly food out to the margin of the stem.  In both the xylem and phloem, the radial system is made up of parenchyma cells.  The ray initials are what produces the radial system.

Receptacle

                    DIAGRAM:  

                          PHOTO:  Composite Flower / Composite Flower / Composite Flower

                                           Narcissus / Narcissus

                                           Fucus / Fucus / Fucus / Fucus / Fucus / Fucus

Receptive Hyphae

                    DIAGRAM:  

                          PHOTO:  Puccinia

Recycling

(as in recycling of nutrients at leaf abscission time)

Red Algae

                    DIAGRAM:  Rhodophyta

                          PHOTO:  

Red Light

(far-red)

Reduction Factors

Redwoods

Regeneration

(tundra)

Regular Flower

Reindeer

Reindeer Moss

Repel

Replication

Reproductive Compatibility

Reptiles

Residual Procambium

The residual procambium is the procambium in the middle of the procambial strand in the dicot stem that does not differentiate.  It eventually becomes the fasciscular cambial portion of the vascular cambium.

                    DIAGRAM:  

                          PHOTO:  Root Cross Section / Root Cross Section

Resilience

Resin Ducts

                    DIAGRAM:  

                          PHOTO:  Pinus Stem Cross Section / Pinus Stem Cross Section

Resins

Various types of organic products of secretory cells in the stems of plants.  In pines, it is the little globs of material in the resin ducts that give pine stems their characteristic pine odor.

Respiration

Reticulate

Reverse

Rhizobium

Rhizoids

                    DIAGRAM:  Psilotum

                          PHOTO:  Moss Stem Cross Section / Moss Stem Cross Section
                                          Equisetum Gametophyte / Equisetum Gametophyte
                                          Fern Prothallium

Rhizome

A rhizome is a modified stem that has nodes and internodes that grows at ground level or just below ground level.  It is thickened because of food storage.  Stems or leaves branch off the rhizome at the nodes.  Roots form by adventitious buds along the lower surface.  Thus, it acts like a perennial rootstock.  A good example is an iris or fern rhizome.

                    DIAGRAM:  Psilotum

                          PHOTO:  

Rhodophyta

                    DIAGRAM:  Rhodophyta

                          PHOTO:  

Ribbed

Ribosomes

                    DIAGRAM:  Microtubules / Rough Endoplasmic Reticulum

                          PHOTO:  

Rind

Ring

(vascular bundle arrangement)

Riparian

RNA Synthesis

Rodents

Root

                    DIAGRAM:  Whole Plant / Shoot/Root

                          PHOTO:  Root Longitudinal Section / Root Longitudinal Section
                                           Root Longitudinal Section / Root Longitudinal Section
                                           Root Longitudinal Section

Root Apex

Root Cap

                    DIAGRAM:  Root Anatomy

                          PHOTO:  Root Cap / Root Cap / Root Cap / Root Cap / Root Cap

Root Hairs

Root hairs are protoplasmic extensions of the epidermal cells.  They greatly expand the surface area of the root so that minerals and water are more easily absorbed.

                    DIAGRAM:  Root Anatomy

                          PHOTO:  

Root-hair Zone

The root-hair zone is the zone in the differentiating root tip where the final maturation and full differentiation of all the cells occurs.  The prominent part of this zone is the root hairs themselves. This is where most of the water and minerals are absorbed by the root.

Root Pressure

Root/shoot ratio

Root Systems

                    DIAGRAM:  Root Systems

                          PHOTO:  

Root Tip

Rosaceae

Roses

Rounded

                    DIAGRAM:  Leaf Apex / Leaf Base

                          PHOTO:  

Rove

(ants)

Rudimentary

(early, non-functional)