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The cell is composed of two major parts, what are those?

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Forest Biology of Tropical Plants Lecture - Marcador

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Forest Biology of Tropical Plants Lecture - Detalles

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The cell is composed of two major parts, what are those?

Living and Non Living

Provides the “mobility” in plants

Pollen and seeds

An aboveground part which includes stems, leaves, buds, flowers, and fruits

Shoot system

A belowground part composed of main roots and branches

Root system

2 Types of Plant tissue systems

Meristematic and permanent

Plants consist of many different types of cells organized into tissues. These tissues are derived from specialized groups of actively dividing cells called

Meristem

Characteristics of meristematic tissues

The cells of meristematic tissue are similar in structure and have thin cellulose cell walls.  The cells may be round, oval, polygonal or rectangular in shape  They are compact, having no intercellular space.  There is a large nucleus and abundant cytoplasm.  The protoplasm contains very few or no vacuoles at all.

This type of meristem is situated at the growing tip of a dicot stems and roots i.e. at shoot apex and root apex.

Apical meristem

In monocots, apical meristems are located at ________

Root tips

As cells in apical meristems divide and elongate, shoot tips and root tips grow longer. This increase in length is called

Primary growth

• These are located at the base of the nodes, internodes, leaves etc. • They are also present in between the permanent tissue. • It produces an increase of length of organ. • Monocots, like grasses, have intercalary meristems which allow the leaves to grow back after mowing

Intercalary meristem

Dividing cells responsible for the lateral growth of the plant. This is also involved in the production of tissues that makes stem bigger in diameter or girth. This is also called secondary thickening.

Cambial Meristem

Three main tissue types

Dermal, Ground and Vascular Tissue

Covers and protects the plant, and controls gas exchange and water absorption (in roots).

Dermal tissue

The site of photosynthesis, provides a supporting matrix for the vascular tissue, provides structural support for the stem, and helps to store water and sugars.

Ground tissue

Transports water, minerals, and sugars to different parts of the plant. It is made of two specialized conducting tissues: xylem and phloem.

Vascular tissue

Specialized pores that allow gas exchange through holes in the cuticle.

Stomata

Based on the function of Ground Tissue (photosynthesis in the leaves, and storage in the roots),

Parenchyma

Based on the function of Ground Tissue (shoot support in areas of active growth),

Collenchyma

Based on the function of Ground Tissue (shoot support in areas where growth has ceased)

Schlerenchyma

Transports water and nutrients from the roots to different parts of the plant, and also plays a role in structural support in the stem.

Xylem tissue

Transports organic compounds from the site of photosynthesis to other parts of the plant.

Phloem tissue

A single cell type plant tissues

Simple tissues

Tissues made from different (aggregates) cell types

Complex tissues.

Simple or complex, act together as a unit to accomplish a collective function and are derived from meristems.

Tissues

Made of cells that are the workhorse cells of the plant body. They do the photosynthesis, load things in and out of the vascular system, hold up the weight of the plant, store things, and generally conduct the important business and housekeeping chores needed to keep the plant body healthy and functioning.

Simple tissues

Three types of simple tissues:

Parenchyma, Collenchyma, and Sclerenchyma

Most abundant and versatile cell type in plants. They have primary cell walls which are thin and flexible, and most lack a secondary cell wall. They are usually somewhat spherical or elongated, but they may have diverse shapes.

Parenchyma cells

Divide and differentiate into all cell types of the plant, and are the cells responsible for rooting a cut stem.

Parenchyma cells

Sites of photosynthesis in leaves

Parenchyma cells

Parenchyma cells are sites of sugar or starch storage in roots

Parenchyma Cells

Basic metabolic functions of cells:

Respiration, photosynthesis, storage, and secretion.

Specialized parenchyma cells with air spaces (large in stems and leaves)

Aerenchyma

Polymer that is embedded between cell wall cellulose molecules, which makes the wall impermeable to water so that water movement occurs only through openings in the cell wall

Lignin

Openings in the cell wall

Pits

Crystals of many different shapes and sizes are usually made in ___________, they are commonly found inside the vacuoles of parenchyma cells.

Calcium oxalate

Are modified parenchyma cells that have many cell wall ingrowths. This enables these cells to improve the transport of water and minerals over short distances between themselves and attached cells. They are found at the ends of files of vascular cells, where they help load and unload sugars and other substances.

Transfer cells

Like parenchyma, lacks secondary cell walls but has thicker primary cell walls than parenchyma. They are long and thin cells that retain the ability to stretch and elongate; this feature helps them provide structural support in growing regions of the shoot system

Collenchyma cells

Highly abundant in elongating stems.

Collenchyma cells

Chloroplasts of Collenchyma cells

Chlorenchyma

The walls of collenchyma cells are composed of _________

Alternating layers of pectin and cellulose.

Compactly arranged, no intercellular spaces, deposition of hemicelluloses and pectin occurs only at the crosswalls separating adjacent cells, usually found in petiole of leaves; cell wall is thickest in two opposite sides (in the bark)

Lamellar

Compactly arranged, no intercellular spaces, deposition of hemicelluloses and pectin occurs only in the angles found in stems, usually below the epidermis, forming a region called hypodermis; cell wall is thickest in corners (herb)

Angular

Spherical or oval, enclose with small intercellular spaces, deposition of hemicellulos and pectin occurs only along the border of intercellular spaces, usually found in the fruit wall

Lacunar

Cells that tend to have thick secondary cell walls due to lignin. They are dead at maturity. Thus, these can no longer stretch, and they provide important structural support in mature stems after growth has stopped.

Sclerenchyma

Occur in aggregates forming a continuous cylinder around stems. They are long, narrow cells with thick, pitted cell walls and tapered ends

Fibers

They may connect end- to-end to form multicellular strands acting like strengthening cables like re-bar in concrete; or they can form a component of vascular tissues. . sometimes very elastic and can be stretched to a degree, but they will snap back to their original lengths.

Fibers

Sometimes occur as sheets but they usually occur in small clusters or as solitary cells. They have many striking shapes, from elaborately branched cells, to star-shaped cells, to the simple stone cells that give a gritty texture to pear fruits.

Sclereids

Vascular tissue system contains two types of conducting tissues that distribute water and solutes

Xylem and Phloem

Consists of an interconnected network of cells that traverse the entire body of the plant.

Vascular system

Complex tissue made up of different kinds of cells that work together to transport water and dissolved minerals.

Xylem

Cell types found in xylem are:

1. water-conducting cells--tracheids and vessel members (the latter join together end to end to make vessels); 2. fibers, for strength and support; and 3. parenchyma cells, which help load minerals in and out of the vessel members and tracheids.

TAKE NOTE: Parenchyma cells are the only living cells found in xylem. (PLEASE CLICK BONUS IN THE RIGHT ANSWER)

BONUS

Function to support xylem tissue and hold it rigid, rather like a steel rod would be used to hold up a plastic water pipe.

Fibers

Not living at maturity. Before the cells die their cell wall becomes thickened with cellulose and lignin, and then the protoplast degenerates.

Tracheary elements

Tiny openings

Pits.

A cell with an oblique, pointed, or transverse end. The ends of mature vessel members are partially or completely digested away during their development to form a perforation plate.

Vessel member

The most common types of perforation plates

Simple and scalariform

Series of vessel members connected end to end. They are often several centimeters long, and in some vines and trees they may be many meters in length.

Vessel

An elongated cell with more or less pointed ends. Tracheids are joined at overlapping ends through bordered pits, and they do not have perforation plates. Both tracheids and vessel members may be present in a single flowering plant.

Tracheid

It is formed in the root and shoot apex very early in organ development.

Primary xylem.

Xylem that forms later in the development of stems and roots is organized in cylindrical patterns

Secondary xylem.

The tissue that transports sugar through the plant.

Phloem

Phloem is made up of several different types of cells:

1. sieve-tube members, 2. companion cells, 3. parenchyma and 4. fibers and/or sclereids (sometimes).

Cells that join at their ends, to form long sieve tubes.

Sieve-tube members

Conducting elements of the phloem, which transport sugars produced by photosynthesis in the leaves to other plant parts.

Sieve tubes

Occurs in vascular bundles near the primary xylem in young stems and leaves and in the vascular cylinder in roots.

Primary phloem

Occurs outside the secondary xylem in older stems and roots, usually in plants that live more than one year.

Secondary phloem

Also known to play an important role in the mechanism of loading and unloading the phloem.

Companion cells

Usually living cells that function in phloem loading and unloading.

Phloem parenchyma cells

The walls of mature sieve-tube members contain aggregates of small pores called

Sieve areas

One or more sieve areas on the end wall of a sieve-tube member is called

Sieve plate

The conducting elements in the phloem. These cells are quite long, with tapered ends. They have sieve areas but no sieve plates at their ends.

Sieve cells

Short, living cells that act as companion cells to these sieve cells.

Adjacent albuminous cells

Refers to the changes that a cell undergoes structurally and biochemically so that it can perform a specialized function.

Cell differentiation

Originate in apical meristems and differentiate into the primary tissues.

Primary meristems

Produce the secondary tissues, which allows vascular plants to grow very large and to great age.

Secondary meristems

Tip of root apex

Root cap

Protects the root apical meristem • Outermost cell layer becomes slimy, eases the movement of the root within the soil • Enables the geotropic growth of the root • Outer cells are continuously worn away, adding new cells to the inner portion. As cells disintegrate they form a strong protective cover.

Root cap

Small, centrally located part of the RAM, divides cell at extremely slow rate- activated during acute stressreplaces the meristematic cells of the rootcap meristem

Quiscent center

Cells divide every 12-36 h toward the edges of the concave dome

Region of cell division

Cells undergo rapid enlargement, i.e. the cells undergo rapid growth in length

Region of elongation

Meristematic and elongation zones are also referred

Region of growth

Cells undergo differentiation into specialized cells (e.g. xylem & phloem) • to anchor the plant • root surface cells mature into epidermal hairs, each with root hair

Region of maturation/differentiation

Three primary meristems that give rise to primary tissues:

Protoderm, procambium, and ground meristems.

Differentiate into the epidermis.

Protoderm

Differentiate into the cells of the primary xylem and primary phloem.

Procambium

Differentiates into the cells of the pith and cortex of stems and roots and the mesophyll of leaves.

Ground meristem

Outer (single) layer of the cells of the young root; it is developed from the protoderm.

Epidermis

Is developed from the ground meristem; cell walls are thickened with suberin and lignin

Cortex

Functions of the cortex

Diffusion of H2O, mineral salts, and O2 from the root hairs inwards • transport water and salts from the root hairs to the center of the root • stores foods reserve (starch)

Innermost layer of the cortex; it is consists of single row of cells; cells more rectangular in shape and the side walls thickened with suberin

Endodermis

It facilitates movement of water from the cortex to the xylem.

Casparian strips

Single layer of thick-walled, tightly-packed cells without intercellular spaces

Pericycle

First primary xylem elements to mature

Protoxylem

Last primary xylem elements to mature

Metaxylem

Shoot system is composed of

Stem and its lateral appendages