chapter 23 - plant nutrition and transport Flashcards
How do plants acquire C, H, O, N, and P?
Carbon comes from CO2 absorbed from the atmosphere.
Hydrogen comes from water absorbed from the roots
Oxygen comes from H2O, CO2, or O2 in the atmosphere or dissolved water.
Nitrogen and Phosphorus are dissolved in water absorbed by the roots
How would planting nodule-producing legumes be useful in crop rotations?
Nodules contain nitrogen-fixing bacteria, such as Rhizobium. These bacteria would raise the nitrogen content available for other crops and reduce the reliance on fertilizers
What are the components of xylem sap?
it contains water, dissolved minerals, and some types of hormones
Trace the path of water and dissolved minerals from soil, into the root’s xylem, and up to the leaves.
water and minerals enter the root through the epidermis and then may move between or within cells of the cortex. once the water and minerals encounter the endodermis, the Casparian strip ensures that all materials enter cells. they next enter the xylem and are pulled up the stem and into leaves. water vapor moves out of the stomata as part of the transpiration stream
How do the cuticle and stomata help plants conserve water?
the cuticle is a waxy barrier that reduces water loss from aboveground plant tissues. guard cells close stomata when conditions are hot and dry, reducing the evaporation of water from leaf tissues
What are the components of phloem sap?
phloem sap is a solution containing sugar, hormones, and other compounds, combined with water and dissolved minerals from the xylem
Explain the pressure flow theory of phloem transport
the pressure flow theory states that phloem moves under positive pressure from sources to sinks. at a source, companion cells load sugars into the phloem’s sieve tube elements. water from adjacent xylem enters by osmosis, increasing the pressure in the phloem. this increased pressure pushes the phloem sap towards sinks, where sugar is unloaded. at a sink, water moves out of the phloem by osmosis, keeping the pressure at the sink low
Distinguish between a source and a sink
a source is any plant part that produces or releases sugars to the phloem
A sink is any plant (typically nonphotosynthetic) that receives sugars in the phloem.
How can the same plant part act as both a source and a sink?
a given plant part that can act as a sink when it receives carbohydrates for storage and as a source when it later releases those carbohydrates to the rest of the plant
Explain why the only effective treatment for mistletoe is to prune off infected branches
knocking off the mistletoe plants will only eliminate the part of the plant that emerges from the branch; the mistletoe can grow back from the parts that were not removed. Pruning away infected branches, eliminates all of the mistletoe
Why can some parasitic plants live without photosynthetic tissues?
it taps into the vascular tissues of its host and steals its sugars. the parasitic plant, therefore, may not need to produce its own sugars by photosynthesis
