Three Basic Transport Mechanisms in Vascular Plants to transfer water, minerals and sugars

Diffusion, Active Transport, and Bulk Flow

36.1: Land Plants Acquire Resources Both Above and Below Ground

Land Plants inhabit two worlds

Above Ground and below ground

Above Ground Shoot Systems acquire sunlight and CO2

Below Ground Root Systems acquire water and minerals

Evolution of Vascular Tissue w/ xylem and phloem

Development of extensive root and shoot systems that carry out long-distance transport

Shoot Systems Stems serve as supporting structures for leaves and as conduits for the transport of water and nutrients

Variation in Shoot Systems Arrangement of leaves, outgrowth of axillary buds, and relative growth in stem length and thickness

Large Leaves Tropical Rainforests

Small Leaves Dry or cold environments

Phyllotaxy Arrangement of leaves on stem important in light capture/

Alternate (Spiral) Phyllotaxy One leaf per node

Opposite Phyllotaxy Two leaves per node

Whorled Phyllotaxy More than two leaves per node

Angiosperms Leaves arranged in an ascending spiral around the stem (137.5 degrees)

137.5 Degrees Angle allows each leaf to get the max exposure to light and reduces shading of the lower leaves by those above

Leaf Area Index Ratio of the total upper leaf surface of a single plant or an entire crop divided by the surface area of the land on which the plant or crop grows

Self-Pruning Nonproductive leaves or branches undergo programmed cell death (due to being shaded too much by higher leaves)

Leaf Orientation Affects light capture

Horizontal Oriented Leaves Low-Light Conditions

Vertical Oriented Leaves GrassLands or Other Sunny Regions

Stem Thickness thick stems = greater vascular flow to the leaves and mechanical support

Thin Stems (Vines) rely on other plants to raise their leaves higher

Root Branching Enable strong anchorage

Taller Plants (Gymnosperms and eudicots)

Anchored by strong taproot systems w/ numerous branches

Small Plants (Monocots) Small due to weaker fibrous root systems as anchors

Mycorrhizae Mutualistic associations between roots and fungi (80% of all plants)

Fungal Hyphae Provides an extensive surface area for the absorption of water and minerals

Stem Elongation (766) Carbon dioxide and sunlight are easilier absorbed through branching (exploitation) Plants have a finite amount of energy to devote to shoot growth

Can not put all energy in branching → will be shaded by taller plants Must find a proper median based off their environment