Stems and Roots Flashcards
Monocot vs dicot differences
-coteyledon
-veins
-vascular bundles
-roots
-petals
Monocot
-1
-parallel
-complexly arranged
-fibrous roots
-in multiples of 3’s
Dicot
-2
-netlike veins
-arranged in ring
-taproot
-multiples of 4 or 5’s
The term secondary growth, includes the formation of …… as well as that of ……. From a layer of ……
Periderm
Secondary vascular tissues
Cambium-cork cambium and/ or vascular cambium
Soft woods in secondary growth consist of
Cortex, resin duct, phloem, vascular cambium, xylem, medullary ray
Secondary growth of hard woods consists of
Cortex, medullary (starch) sheath, xylem tissue, vascular cambium, phloem tissue, endodermis, cortex, periderm, cork cambium (phellogen) ,cork (phellum)
Environmental adaptations to stems
Epidermis, outer and inner cortex, lamellae, air chambers, idk blasts and stele-like zone
Storage stems (and leaves) examples
Bulb, stem tuber, corm, rhizome
Primary and lateral roots
Primary are the larger roots in which the lateral roots join off of
What develops from the pericycle
Secondary or lateral roots
Adventitious roots
Any root that arises from an organ of the plant, or an area of the embryo other than the primary root (ex: arise from stem)
Prop rots of corn, mangrove trees, banyan greets
Firbrous root system
Mycorrhizae
Mycorrhizal fungal filaments radiating from a mycorrhizal colonized root
The primary structure of the stem is divided into 3 tissue system:
Dermal -epidermis and peridermis
Fundamental - parenchyma, collenchyma, chloenchyma
Vascular -phloem(sieve tubes) and xylem (tracheids and vessels)
Which three meristematic tissues are initiated by the apical meristem of the stem
Protoderm- forms epidermis
Procambium- forms primary vascular tissue
Ground meristem-produces fundamental tissues
Grandular and non grandular trichomea
Grandular have a Grandular head and secrete secondary metabolites (long, uni-seriate)
Non Grandular have no Grandular head and protect from UV (short, multi-seriate)
Secondary growth main focus
Increases the amount of vascular tissues in stem, beginning with the part of the shoot or seedling axis that has ceased to elongate. Contributes primarily to thickness of the axis but may be observed in limited amount in the leaves, particularly petiole and the midrib.
Formation of periderm and secondary vacuole tissue
Which plants are examples of ones that exhibit secondary growth
Gymnosperms, woody Eudicots
Some herbaceous eudicots and most monocots have no____
Secondary thickening
Coniferous woods (soft woods) have _____ as the main structural element in their composition
Tracheids
Many herbaceous anthophyta develop secondary growth as they ______ and therefore start to resemble _____
Grow older
Young woods anthophyta
Lenticels function
Function as passages to the inner stem tissues are are used for gas exchange
Special stem structures
Leaf abscission
Dark band crossing the base of a petiole (joins the leaf to the stem)
The region of the leaf stalk in which a corky layer forms and weakens the attachment of the leaf to the stem which will eventually break off.
Special stem structures
Geophytes
Underground storage organs and the plants that bear them
-contain overwintering (perennating) buds from which new growth will arise.
Geophyte storage organs
Bulbs, corms, tubers and rhizomes
Bulbs
A true bulb, such as an onion, consists of fleshy layers of leaves that store food for the developing plant. The roots at bulbs base anchor the plant in the soil and absorb nutrients. The central tip of the top of the bulb is the bud from which leaves eventually emerge.
Daffodils, tulips, Lillie’s and garlic
Corms
Such as gladiolus, contain a solid mass of vertically compressed stem tissue, rather than concentric rings of leaves.
Tubers
A swollen stem. Shoots develop from the buds or eyes on the potato. If you cut the river into pieces; each piece will develop into a mature plant so long as the cut piece has at least one eye.
Potatoes
Root tubers
Develop from the root rather than the stem
Potato tuber
All parts of the normal stem, including nodes and internodes.
The nodes are the eyes and each has a leaf scar (eyebrow). Nodes are arranged around the tuber in a spiral way. Internally, a tuber is filled with starch stored in enlarged parenchyma-like cells.
Stem tuber of potato
Has same stem structure with pith, vascular zones and a cortex
Rhizomes
Scaly, horizontal underground stems. Example is a fern, from which upright shoots arise.
Some are swollen storage organs like in ginger and irises
Function of roots
-anchorage
-absorption
-storage
Conduction
Biennials
Plants that complete their life cycle over a two year period
Sugar beets, carrots
Large food reserves accumulate in the storage regions of the root during first year and then are used during the second year to produce flowers, fruits and seeds.
A seed is a completele ____, _____ plant
Dormant
Miniature
At maturity, the embryo is differentiated into a rudimentary shoot called the _____; one or two specialized seed leaves or _____ and a root or _____. The axis of the embryo above the seeds leaves which gives rise to the stem and its origins is called the _____. The transition zone between the raid led and the plumule is called the _____
Plumule
Cotyledons
Radicle
Epicotyl
Hypocotyl
The radicle develops into the _______ even before the seed _____
Root cap, apical meristem, Protoderm, Procambium and ground meristem
Germinates
Which of the radicle differentiated parts is not compromised of meristematic cells
Root cap
Apical cell
Most distal structure in the root and gives rise to the remainder of the root system
The tip of the root is covered by a ____ which _____
Root cap
Protects the apical meristem behind it and aids the root in its penetration of the soil
As the root grows longer and the root cap is pushed forward, the cells on the periphery of the root cap are ______
Sloughed off which form a slimy covering around the root and lubricates it’s passage through the soil
As quickly as the root cap cells are sloughed off…..
New ones are added by the apical meristem
Functions of root cap
Protecting apical meristem
Aiding penetration
Controlling the response of the root to gravity
Geotropism
Controlling the response of the root to gravity. Since it goes in the direction of gravity, it is known as positive geotropism
Apical meristem produced cells into regions of cell division a short distance beyond the meristem. There are ____ regions or primary meristems which give rise to the permanent tissues of the root:
3
Procambium-rise to vascular tissue
Protoderm-rise to epidermal tissue
Ground meristem-fundamental tissue
Region of cell division
Combination of the apical meristem and the nearby portion of root in which the cell division does occur
Behind the region of cell division, but not sharply delimited from it, is the
Region of elongation
Measures only few millimeters. Results in most of the increase length of the root. Beyond this region the root does not increase in length
Region of elongation is followed by the _______
Region of maturation
Most of the cells of the primary tissues mature. Root hair are also produced here. Therefore it’s sometimes called the root hair zone.
Which zone has the most water absorption
Root hair zone
Primary root
First external root of the plant originated from the radicle and is called the primary root
-taproot in gymnosperms and eudicots
In monocots, the primary roots is usually short lived. The main part of the root system develops from the _______ that arise from the_____
Adventitious roots
Base of the stem
______ systems generally penetrate deeper into the soil than do_____
Taproots
Fibrous root systems
In aquatic plants, absorption is undertaken primarily by the
Foliage and stems
Aquatic macrophytes
Large, submerged aquatic plants
The major problem for all submerged plants is ______
What is used to help
Attainment of sufficient oxygen
Air chambers extending from the shoots and leaves to the roots.
Pneumatophores
Spongy, negatively geotropic, aerating roots which are found in some plants growing in water-logged, badly aerated soils. They arise above the surface of the water and are perforated by many lenticels
Facilitate gaseous exchange between the air and the subsurface roots to which they are attached.
Emergent macrophytes
Large, aquatic or semi-aquatic plants with aerial parts
Epiphytes
Plants which grow attached to other plants
Ex: orchids
Have aerial roots which are exposed to the air. A large multi-layered epidermis on the outside surfaces of the roots (velamen) acts as water storage tissue and is a buffer zone which helps to reduce water loss
Hydrophilic velamen function in different weather
Retain moisture in roots in low humidity
Absorb moisture from air in high humidity
Clasping roots
Aerial roots develop at stem nodes.
They are modified adventitious roots
Crampons
Clasping Roots if Virginia creeper that have terminal suckers
Buttress roots
Common in large tropical trees. Occur at the base of the trunk where the main roots branch off at the ground surface and enter the substrate.
Immense, exaggerated wall-like structures at the interface between the truncheons and the ground. Their function is to provide additional support to the stem
Prop roots
Adventitious roots that form above the primary root at the nodes on the main stem or it’s branches. Woody prop roots from the horizontal branches of the banyan tree grown out of the branches and dangle vertical led downward and penetrate the soil=stilt roots
Tuberous roots
Storage organs which act as overwintering organs in environments which have extreme fluctuations of either temperature or moisture.
Fascicled
Clustered or branched
Contractile roots
Monocots mainly but some herbaceous, perennial eudicots
-pull the shoot closer to the found or in the case of bulbs into the soil. The shortening of the root comes about through radial expansion and longitudinal contraction of inner cortical cells. The central vascular tissue becomes contorted because it is not involved in growth.
Makes difficult to take out of ground like dandelions!!!
Haustoria
Adventitious roots that develop alone the stem in in contact with the host plant and establish connections with the vascular system of the host.
Ex: dodder
Mycorrhizae fall into two groups
Extomycorrhizae
Endomycorrhize
Ectomycorrhizae
Entire root tip is surrounded by a dense mantle of hyphae which penetrates the intercellular space
Endomycorrhizae
Fungus forms a very thin mantle but whose hyphae invade both the inter and intracellukar spaces
Fungus and plant mutualistic benefits
Fungus breaks down complex organic molecules in the substrate that the plant can absorb.
The root provided the fungus with sugars and amino acids.
Association of bacteria (rhizobium) with roots of legumes are very common.
How does it work?
The bacteria infect the roots and utilize nitrogen from the atmosphere, fixing it into a form that becomes available to the plant and to the bacterium itself.
Common method of vegetative propagation
Induction of adventitious roots
Rooting if a stem which is still attachment to the parent plant =layering
Newly rooted part has been detached from its parent plant = propagation from cuttings
Interfasicular cambium
Area between vascular bundles
Where is the vascular cambium located
Between phloem and xylem
What does a medullary ray look like under a microscope
Blue line running out of vascular bundle
Aquatic plant adaptations
-air chambers to help with buoyancy and carry oxygen to root zone
-thin cuticle that allows passive transport throughout plant
-stele has less obvious vascular tissue as it is not necessary to be rigid with sclerenchyma when water holds it up
-reduced vascular bundles
Mucilage cells
Secrete mucous to help prevent water loss in cactus
-located in parenchyma
Adaptations for xeric plants
-mucilage cells
-thick cuticles to prevent water loss
Do the vascular bundles in stems and roots have to be the same?
Nope
Velamen
Moisture storage protector in epiphytes
Woody anthophyta xylem vs coniferous
Woody has tracheids, vessels, woof fibres, xylem parenchyma and raya
Coniferous have tracheids
-no vessels
-no wood fibres
