Week 9 Structural Adaptations

What are the three tissue systems of a plant?

dermal

ground

vascular

What is the difference between parenchyma, sclerenchyma, and collenchyma? Whichis undifferentiated? Which is dead a maturity? Which provides flexible support?

parenchyma- generic, variable

collenchyma- provides flexible support

schlerenchyma- cell wall, rigid support, dead at maturity

Where might you find parenchyma, sclerenchyma and collenchyma tissue?

ground tissuexylem

What is the function of xylem? What is the function of phloem? Which of these twotissue types is dead at maturity?Structural Adaptations

xylem- dead at maturity, moves water up

phloem- moves sugar around

Why might many plants be phenotypically plastic?

grow different depending on the environment

What are several morphological differences between a sun and shade leaf?

sun leaves are thicker with more pallisade parenchyma

What is lignification and how does it lead to sturdy plants?

lignin makes plants tough

Often when you submerse a plant stem it becomes thicker yet less sturdy, explainwhy?

less lignin, more air space

Where do you commonly find the stomata on floating leaves and how is that different from where stomata are generally found on emergent leaves?

floating- on top

terrestrial- on bottom

submersed- absent

Why might chloroplasts occur in the epidermal layer of submerged leaves but not emergent leaves?

light is less common underwater

What are several characteristics that are common to floating leaves?Note floating leaves are generally thicker than terrestrial leaves and submerged leaves are among the thinnest leaves (of course these are generalization).

• stomata typically adaxial

• chloroplast-rich upper palisade layer

• regularly arranged spongy layer withcolumnar supports to produce a largenetwork of air-spaces

• support of chambers by branching sclereids

• phloem better differentiated than xylem

• both epidermal layers cutinized and may possess chloroplasts

What are several characteristics of submersed leaves?

• lack mechanical tissue (supported by water)

• cuticle thin or absent; lack of epicuticular (surface)wax layers

• stomata lacking or functionless

• mesophyll reduced; often a single cell layer or absent

• more chloroplasts in epidermis

• xylem greatly reduced or absent

Why are submergent dicots typically dissected, while submergent monocots are ribbon-like?

convergent evolution

Why is a high surface area to volume ratio important underwater?

more light and CO2 uptake

Why is the xylem of submerged plants often reduced or absent?

they do not need to take up water

Why is the cuticle reduced or absent in submerged plants?

to suck in CO2

Why might a broad flat submerged aquarium plant start to develop small pits on itsupper surface?

limited CO2