biology - experiment 7 - leaves

8/3/2019 Biology - Experiment 7 - Leaves

1/19

EXPERIMENT 7: LEAVES


2/19

PARTS OF A LEAF:


3/19

SIMPLE & COMPOUND LEAVES


4/19

LEAF MODIFICATIONS

Bulbous petiole enable the plant tofloat.

Eichhornia crassipes

Colored Bracts protect the flowerfrom pests & harshweather.

Bougainvillea glabra


5/19

Spines of cactus forprotection, absorbs

moisture from the air.

Carnegia gigantica

Tendrils of a squash help the plant climb

up to reach moresunlight.

Cucurbita maxima


6/19

Leaf base of anonion for storage.

Allium cepa

Stipules of Gumamela protect the young

leaves.

Hibiscus rosa-sinensisLinn


7/19

Fleshy leaves of Aloe Vera for asexualreproduction.

Aloe barbdensis


8/19

CROSS SECTION OF A MONOCOT LEAF


9/19


10/19

CROSS SECTION OF A DICOT LEAF


11/19

GUIDE QUESTIONS:

Briefly describe how leaves are formed.

Leaves are formed from the leafprimordium. More cellular divisions andexpansions produce an apical peg, which hasan apical meristem and a procambial strandthat forms the leafs midrib. The leaf the forms anadaxial meristem that thickens the leaf. Then theleaf forms an upper and lower leaf zone. The

upper lead zone contains marginal meristemwhich increases the surface area of the leaf.


12/19

Briefly describe the ligule and itsfunction.

A ligule is a thin, membranousout growth from the base of theblade of most grasses. This excludeswater from draining down the mid-rib of the leaf blade into the pocket

of space between the leaf sheathand the internodal groove causedby divergence of the axillary bud. Indoing this, the ligule also excludes

conditions for possible stalk rotinfection and allows the axillary budto develop and respire.


13/19

Define the following:

leaf trace - A strand of vascular tissue that extendsbetween the vascular bundle of a stem and a leaf.

abscission zone where the transformation of a corklayer results in the separation of that part from the plantbody.

deciduous plants tree or shrubs that lose their leavesseasonally.

Thigmotropism- is a movement in which an organismmoves or grows in response to touch or contact stimuli.


14/19

prophylls tiny reduced leaves near the base of alateral branch.

leaf dimorphism occurrence of morphologically

distinct leaves on the same plant. fronds leaves that are usually formed in a curled

structure called a fiddlehead.


15/19

Briefly compare the cross-section of a monocotand dicot leaf.

Dicot leaf the vascular bundles are not inparallel series and are supported by bundle sheathextension. The mesophyll is differentiated into

palisade and spongy mesophyll.

Monocot leaf the vascular bundles are inparallel series and are supported by sclerenchyma

patches. It has a uniform mesophyll.


16/19

Does your observation on the vascular tissuearrangement of a monocot and dicot stem andleaf indicate continuity of vascular tissues in theseorgans? Briefly explain your answer.

Yes, in dicots there is a continuity of vasculartissues because the venation is netted and areconnected. In monocots, there is no continuity sincethe veins are not connected.


17/19

Compare the distribution of the stomata in theupper and lower epidermis of a horizontally and avertically oriented leaf.

Horizontally oriented leaf there are morestomata at the abaxial epidermis.

Vertically oriented leaf the stomata aredistributed evenly.


18/19

Briefly compare the leaves of hydrophytes andxerophytes.

Xerophytes small, thick leaves with well-developed spongy and palisade layers. These leavesare modified for storing water. These are found indeserts.

Hydrophytes large, thin leaves with poorlydeveloped spongy and palisade layers. These leavescontain large amounts of aerenchyma. These areaquatic plants.


19/19

Give three economic importance of leaves.

Sources of medicine.

Sources of fuel because some leaves containflammable resins that can be used as fuel.

Sources of fibers which are woven into ropesand fabrics prized by clothiers and sailors.

biology - experiment 7 - leaves

Documents