DFF lecture 29

On your walk home one afternoon you notice an herbaceous plant with an interesting-looking form. Its branches have repeating leaf-petiole units attached to a central stalk. Which observation would lead you to believe you were looking at simple leaves rather than a compound leaf? There are no axillary buds between the petiole and the stalk. There is a terminal bud at the end of the stalk. There are axillary buds between the petioles and the stalk. There is no terminal bud at the end of the stalk. The stalk lacks leaf primordia.

There are axillary buds between the petioles and the stalk.

Which structure is mostly composed of sclereids? Redwood tree bark Acorn shell Carrot root hair String in celery Tomato trichome

acorn shell (think: thick, secondary cell walls)

what does the vascular cambium meristem do?

adds additional phloem and xylem to preexisting vascular bundles, increasing the diameter of the plant and therefore aiding in secondary growth it kinda squeezes in secondary xylem and phloem

where does primary growth occur in plants?

at the shoot apical meristem and root apical meristem (NOT the entire plant)

what are bud scales and what role do they play?

bud scales are a bunch of tiny modified leaves formed by the meristem that surround the shoot apical meristem. They're present throughout the winter to protect the shoot apical meristem and then fall off in the spring when it starts growing again, and they leave a scar where they fall off NOT photosynthetic

put in order from outer to inner in a plant: elongation, cell division and differentiation

cell division, elongation, differentiation

guard cells

cells on the lower epidermis that open/close pores (stoma) to limit water loss

how can we visualize growth in a stem?

in the spring, there is a lot of water availability so the cells are big and lighter, and in the summer dryness the cells are smaller and darker, and in the winter there is no growth at all. So this allows you to see the boundaries between years of growth- patterns between light (spring) and dark (summer)

the pericycle is farther _________ than the endodermis.

inside The pericycle arises from procambium and is the outermost part of the vascular cylinder the endodermis is NOT part of the vascular cylinder but is directly outside it (endodermis contains Casparian strip)

how does the vascular cambium make the different tissues?

kinda like a stem cell! whenever it divides, it'll make one cell that stays cambium and one that can differentiate into either a new xylem (inner) or phloem (outer) cell. This repeats many times this thickens the stem

pericycle is the origin of ____________ roots

lateral

how do meristems compare to mature leaves?

meristems are growing points at the very tips of roots and shoots and are undifferentiated and rapidly dividing, while in mature leaves, all cells are differentiated and cells aren't dividing

does the vascular cambium ALWAYS continually divide to add xylem and phloem?

no, only throughout the growing season

do wood and bark both get thicker?

no- wood (xylem) gets thicker every year but bark (phloem) maintains constant thickness

describe the anatomy of a root

outside layer: epidermis cortex (middle layer): ground tissue center: vascular tissue called stele that contains xylem and phloem pericycle is part of the stele and is the origin of root branches endodermis = C cortex root apical meristem is at the tip and has actively dividing, undifferentiated cells pushing through the soil. There is a root cap outside of it to protect the apical meristem. sl 24!

palisade vs spongy mesophyll cells

palisade mesophyll cells are on the upper surface of a leaf and are tightly packed, while spongy mesophyll cells are less tightly packed and have lots of air spaces which line up with the gaps in the lower epidermis for gas exchange

primary vs secondary growth

primary growth is the increase in length of root and shoot, while secondary growth is increase in width (thicker)

how do vascular bundles differentiate?

procambium differentiates into xylem at one end and phloem at the other, and they slowly make their way in until either the entire bundle is differentiated into xylem and phloem or there is some vascular cambium left in the middle the vascular cambium is necessary to further differentiate throughout life

where are new root daughter cells produced?

root apical meristem most daughter cells differentiate into the primary tissues of the root (like epidermis, ground, etc.)

what are the 3 kinds of meristem?

shoot apical, root apical, and vascular cambium

leaf anatomy

top to bottom: cuticle, upper epidermis, palisade mesophyll cells, vascular bundles (with xylem and phloem), spongy mesophyll cells, lower epidermis, cuticle

procambium cells

undifferentiated cells in the vascular bundles that will give rise to phloem and xylem on opposite ends of the bundle

meristem

undifferentiated tissue in plants that is rapidly dividing to form new tissue- can be located at root, shoot or in cambium

xylem and phloem are contained within the ____________ ___________

vascular bundles

how can we know how old a twig is?

where the bud scales fall off every spring, they'll leave a scar, so you can determine how many years old it is by the number of scars left by bud scales

pericycle

The outermost layer in the vascular cylinder, from which lateral roots arise. part of the stele

where is the vascular cylinder found? What's contained in it?

found in the very center of roots, and within it is alternating xylem and phloem

vascular cambium

growth tissue in stems and roots that produces secondary xylem (inwards) and secondary phloem (outwards)

what 2 things stick out of the root and what are their functions?

1. root hair- single cell that increases the SA of the root and improves its ability for water absorption 2. root branches/lateral root- multicellular and has the same structure of the root it came from, and has those same layers of tissues

what does the ground tissue in a leaf consist of?

2 kinds of mesophyll cells- palisade mesophyll (tightly packed) and spongy mesophyll (lots of air spaces)

You extract cells from an unusual-looking leaf. Some of the cells appear to lack chlorophyll and contain large vacuoles. How would you classify these cells? Please choose the correct answer from the following choices, and then select the submit answer button.

epidermal

all angiosperms have the same stem anatomy except for what one difference?

the arrangement of vascular bundles eudicot: arranged in ring monocot: peppered throughout entire stem cross section but the individual bundles aren't fundamentally different

compare the upper and lower epidermis

they both provide an interface between the rest of the leaf and the air surrounding it, but the upper epidermis is completely sealed, while the lower epidermis has gaps with specialized cells for gas exchange

xylem cells have ________ walls, while phloem cells have _______ walls. Therefore...

thick; thin xylem becomes wood (thicker), phloem becomes bark (thinner)