Bot-Lab (Sem-1) - Chapter 14: The Leaf

leaf

main photosynthetic organ of plants; often described as flattened, laterally spread and green

xylem

water-conducting tissue

phloem

food-conducting tissue

chlorenchyma

photosynthetic parenchyma; strategically located within the blade in the mesophyll layer

mesophyll

the layer in which chlorenchyma cells can be found

dorsi-ventral leaf

leaves where stomata are confined to the lower epidermis

isobilateral leaf

leaves where stomata are on both the lower and upper epidermis

Poaceae

grass family

Fabaceae

legume family

Malvaceae

cotton family

leaf morphology

based on the foliage leaf; highly variable across major plant groups

leaf blade/lamina

flat, light-harvesting portion of the leaf

abaxial surface

the blade’s lower side/dorsal surface

adaxial side

the blade’s upper side/ventral surface

midrib

the large central vascular tissue of the leaf

midvein

other term for midrib

veins

arise from the midrib and supply the blade

petiole

the stalk that attaches a leaf to the node of the stem

sessile

leaf without a petiole

monocot leaf

characterized by parallel venation

simple parallel venation

the veins run alongside each other from the base to the tip

leaf sheath

a clasping sheath that attaches the monocot leaf to the stem; base attachment encircles the whole stem, hence, ring-like nodes

Bambusa sp.

bamboo

penni-parallel venation

veins are arranged on both sides of the midrib in parallel direction like barbs of feathers

Musa sp.

banana

(parallel) palmate venation

veins arise from a common point and radiate in a parallel fan-shape fashion to the tip

Sanbus rotundifolius

anahaw

obsolete venation

mostly observed in succulents; veins are not visible

Sanseveria sp.

snake plant

Aloe vera

leaf spines; succulent leaves; sabila

eudicot leaf

a type of leaf with netted venation

stipules

two small flaps of tissue at the base of the petiole

netted venation

branching/reticulate veins arise from one large midrib

Psidium guajava

opposite phyllotaxy; guava

(netted) palmate venation

netted veins that arise from the base of the midrib

Carica papaya

papaya

simple leaf

consists of a single unincised blade/incised incision does not reach up to the midrib

compound leaf

made up of several leaflets; incisions reach up to the midrib or to the tip of the petiole; leaflets are ALWAYS arranged in two rows and never in spiral, whorled, or decussate phyllotaxy

petiolule

the “stem” that attaches the leaflet to the primary rachis

primary rachis

an extension of the petiole of a compound leaf that bears the leaflets; never have a terminal bud

secondary rachis

branches of the primary rachis

tertiary rachis

branches of the secondary rachis

pinnately compound; palmately compound

types of compound leaf

pinnately-compound leaf

the lamina is incised up to the midrib which gets modified into a rachis bearing leaflets laterally

unipinnate; bipinnate; tripinnate

types of pinnately compound leaves

unipinnate

leaflets arise on the primary rachis; even-pinnate if the number of leaflets is in even number; odd pinnate if the number of leaflets is odd

even-pinnate

a unipinnate leaf with 2 terminal leaflets

Cassia alata

candle bush; asunting

Arachis hypogea

peanut

odd-pinnate

a unipinnate leaf with 1 terminal leaflet

Rosa sp.

rose

bipinnate

type of pinnately compound leaf when the primary rachis branch one and leaflets arise from the secondary rachis

Delonix regia

firetree

Leucaena leucocephala

ipil-ipil

tripinnnate

type of pinnately compound leaf when the secondary rachis branches and the leaflets arise from the tertiary rachis

Moringa oliefera

malunggay

palmately compound leaf

all the leaflets arise from a common point; becomes incised up to the petiole; leaflets appear like articulated fingers

unifoliolate; bifoliolate; trifoliolate; quadrifoliolate; pentafoliolate; multifoliolate

types of palmately compound leaf

unifoliolate

palmately compound; a single leaflet; two lateral leaflets are suppressed and only the central leaflet becomes functional

Citrus sp.

pomelo

bifoliolate

palmately compound; with double leaflet

Pyrostegia venusta

flametree

Phaseolus sp.

bean

trifoliolate

palmately compound; with triple leaflets

Erythrina variegata

dapdap

quadrifoliolate

palmately compound; with four leaflets

Marsilea sp.

water clover

pentafoliolate

palmately compound; with five leaflets

Schefflera sp.

lima-lima

multifoliolate

palmately compound; more than five leaflets

Ceiba pentandra

kapok

dorsi-ventral/bifacial leaf

a feature of most eudicots; horizontal in orientation; a distinct upper and lower surface

mesophyll

distinctly divided into a palisade mesophyll and spongy mesophyll

palisade mesophyll

composed of tall cells vertically oriented to the leaf surface

spongy mesophyll

composed of irregular parenchyma with a lot of intercellular spaces; where the stomata are confined

guard cells

cells that regulate the opening and closing of the stomatal pores

stomatal pores

openings on the leaf’s surface flanked by guard cells that regulate moisture

crypts

areas where the epidermis is depressed

x-s of Ixora finalysoniana leaf

identify the specimen

x-s Adelfa (Nerium oleander) leaf

identify the specimen

petiole

considered as transition between the stem and the lamina (leaf blade); epidermis contain fewer stomata and trichomes than lamina; non-aerenchymatous mesophyll

leaf traces

the convergence of the stem and petiole

leaf gaps

parenchymatous regions located adaxially from the diverging leaf traces

x-s petiole of Schefflera

identify the specimen

x-s petiole of Citrus

identify the specimen

isobilateral/equifacial leaf

vertically-oriented leaf; distinction between upper and lower surfaces of the leaf is absent; mesophyll is usually indistinguishable

amphistomatic

having stomata on both sides of the blade

x-s of Eucalyptus leaf or Callistemon

identify the specimen

x-s of the corn (Zea mays) leaf

identify the specimen

phyllotaxy

the arrangement of leaves on stem; important in positioning leaves so that they will not shade each other

alternate; opposite; whorled

three types of phyllotaxy

alternate phyllotaxy

only one leaf attached to the node, alternating up the stem

Chrysophyllum cainito

alternate phyllotaxy; caimito

opposite phyllotaxy

two leaves attached per node

whorled phyllotaxy

three or more leaves per node

Nerium oleander

whorled phyllotaxy; adelfa

specialized leaves

leaves that become modified and perform other functions

tendrils

threadlike sensitive structures that coils on a surface and gives support to the plant

Ipomoea cairica

tendrils; morning glory

Clitoria ternatea

tendrils; butterfly pea