PBL 2: Meristems and Plant Tissues Flashcards

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1
Q

Plant tissue and types

A

Plant tissue: collection of similar cells conducting the same function

Types:
-Permanent tissues, which lost their ability of cell division
-Meristematic tissues, actively dividing cells.

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2
Q

Simple permanent tissue

A

Only have primary walls, made of cellulose+hemicellulose

-Parenchyma: Most common, permeable,
weak
-Collenchyma: Unevenly thickened wall, plastic support, can be reshaped
-Sclerenchyma: Primary+ thick secondary wall, elastic support, maintains the leaf’s shape

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3
Q

Complex permanent tissue

A

More than one type of cell, i.e:
-Epidermis: the outermost layer, consists of a single layer of parenchyma cells, covered by wax and cutin.

-Ground tissues/cortex: internal layer to the epidermis, parenchyma that later undergoes photosynthesis.

-Pith: Internal to the vascular tissue
-Vascular tissue: Xylem+Phloem

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4
Q

Epidermis Function

A

-Transpiration, protection from bacteria, insects, fungi.
-Reflective to prevent overheating
-Gas exchange
-Can have trichomes: protection, prevents water loss, can contain chemicals

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5
Q

Ground tissue Function

A

Food storage, transportation, secretion, photosynthesis
-Aerenchyma cells: allows for plant to flow on water by filling intercellular spaces with air.

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6
Q

Xylem

A

Dead and hollow sclerenchyma cells, conduct water+minerals, made of tracheids and vessel elements.
-Only flows in one direction

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7
Q

Tracheids

A

Transfer water via pit membranes (tracheids overlap), found in flowering plants and ferns.

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8
Q

Vessel Elements

A

Provide movement of water with less friction due to perforations in primary walls.
-Perforations of adjacent cells align and form a vessel

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9
Q

Phloem

A

Distributes sugars+minerals, no secondary walls, living cells.
-Flows in any direction
-Accompanied by companion cells with nucleus

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10
Q

Sieve Elements

A

Made up of sieve tube elements and sieve cells.
-Parenchyma cells, living cells with cytoplasm, no nucleus, enlarged plasmodesmata called sieve pores.

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11
Q

Sieve Cell

A

Elongated and spindle shaped cell with sieve areas.
-Associated with albuminous cells

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12
Q

Sieve tubes

A

Stacked cells with aligned sieve areas (sieve plates) on bottom+upper end
-Have companion cells, which lead sugars in and out of cell

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13
Q

Apical Meristem (Meristematic tissue)

A

Growth of the tips of the roots+shoots, produced primary meristems and then primary tissues.

Process of cell division: One cell remains meristem, the other one becomes the primary meristem, the latter of which can differentiate into:
1. Provascular tissue: xylem+phloem
2.Protoderm: epidermis
3.Ground tissue: pith+cortex

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14
Q

Lateral Meristem (Meristematic tissue)

A

Responsible for secondary tissue growth in stem+roots,
-Increases stem & roots in diameter

Structure: In the vascular bundle,
1. the xylem is internal to the phloem
2. In between this is the vascular cambium
3. The fusion of cambium cells forms a ring.

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15
Q

Vascular cambium (meristematic tissue)

A

Consists of two cell types:

  1. Fusiform initials:
    -thin primary wall, longitudinal cell division, produces two cells: (one remains meristem, other develops into phloem/xylem depending on position)
  2. Ray initials:
    -short+cubica, storage&transport function between xylem and phloem, and vice versa
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15
Q

Cork cambium (meristematic tissue element)

A

Produced when cells die and parenchyma cells are reactivated in the external layers:
-serves as a protective layer, production of phloem cells.

16
Q

More info on the cork cambium

A

-Cell division: inner cell remains cork cambium, outer cambium becomes cork cell (periderm=cork cell layers)

-Mature cork cells produce suberin (waterproof)
-Regions (lenticels) allow for gas diffusion into intercellular spaces.

17
Q

Growth ring

A

Cambium cells that keep adding new layers of phloem+xylem