CH25: Shoots Structure and Development + Leaves Flashcards
What are found at shoot nodes?
At each node, one or more strands of the vascular cylinder of the stem turn outward and extend into the leaf, leaving one or more gaps in the vascular cylinder opposite of the leaf. There are no such gaps in the vasular cylinders (protosteles) of roots.
How does the arrangement of monocot and dicot stem vascular tissue differ?
Monocot: have a number of vascular bundles scattered throughout nonconducting stem tissue
Dicot:
- herbaceous eudicots have discrete vascular bundles arranged in a ring
- vascular bundles are separated by only a very thin layer of cells and so appear as a cylinder
Where is pith likely to be located in herbaceous stems?
The “middle” of the stem, taking up most of the space and separating the vascular bundles.
What tissue type supports the outside angles of herbaceous stems?
The several layers of collenchyma cells, which provide support to the stem, form a continuous cylinder beneath the epidermis.
What are the primary purposes of the stems?
Support and conduction
What are the modified stem types that rest on the ground or grow below ground?
Rhizomes
What is a modified cactus stem modified to do? What are the leaves modified to do?
The green, fleshy stems serve as both photosynthetic and storage organs. The water-storing tissue consists of large, thin-walled parenchyma cells that lack chloroplasts.
The modified leaves are hard, dry, and nonphotosynthetic: spines. They serve to protect the stem
Mesophytes
Plants that require an environment that is neither too wet nor too dry
Hydrophytes
Plants that require a large supply of water or grow wholly or partly submerged in water
In leaves of hydrophytes that float on water, stomata may occur in the upper epidermis only.
Submerged leaves usually lack stomata entirely.
Xerophytes
Plants adapted to arid habitats.
Contain greater number of stomata (higher rate of gas exchange during rare periods of water supply). Stomata are sunken in depressions on the lower surface of leaves and the depressions may also contain trichomes.
What is the name of process that moves water from the ground up through roots, stems, and out through stomata?
Where do phloem proteins/slime plugs form? Why?
What is the function of the stem?
- An attatchment point for buds, leaves, flowers, fruits/cones
- elongation above ground
- increase surface area and mass
- conduct water, minarals, and organic compound between leaves and roots
What are sources and sinks in regards to phloem loading?
Where are palisade and spongy parenchyma of the mesophyll located in leaves?
