1、Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Roots,Chapter 5,Copyright McGraw-Hill Companies PermissionRequired for Reproduction or Display,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Outline,Root Function Roo
2、t Development Root Structure Specialized Roots Mycorrhizae Root Nodules,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Function,There are several functions for a root Anchorage Water and mineral absorption/conduction Storage Starch Water Extensive undergrou
3、nd organ A single grass plant 15 x 106 roots = 400 miles of root / 2 ft3 soil,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,How Roots Develop,When a seed germinates,
4、the embryos radicle grows out and develops into the first root.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Radicle,Root development,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Development: Tap root - Fibrous
5、 root,May develop into thick taproot with branch roots. Dicotyledonous Plants May develop a fibrous root system. Monocotyledonous PlantsAdventitious roots are roots that develop from non-root plant partsBoth monocots and dicots,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGr
6、aw Hill Companies,Adventitious Roots,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,What are the advantages and disadvantages of a fibrous and a taproot root system?,Advantages,Fibrous Large surface area, increased access to water and minerals Taproot Good
7、for a storage of nutrients, can access water and nutrients at great depths, good during drought periods,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Disadvantages,Fibrous Does not reach water and nutrients deep in soil profile - not good during drought No
8、t good for storage of water or carbohydrates Taproot Not as efficient as fibrous at getting water & minerals in upper soil profile.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,ROOTS,Root Function Root Development Root Structure Specialized Roots Mycorrhi
9、zae Root Nodules,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Root Structure,Root Cap Region of Cell Division Region of Cell Elongation Region of Cell MaturationNot all regions well-defined at their boundaries. Development in roots unlike other organs fol
10、lows a linear vector,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Root Structure and Root Tissue Comparison,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Root Structure,Root Cap - Thimble-shaped mass of parenchy
11、ma cells covering each root tip. Protects tissue from damage. Function in gravity perception. Cells secrete a slimy substance and slough off forming a slimy lubricant that helps roots move through soil,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region o
12、f Cell Division,Root apical meristem 12 to 36 h cell cycle,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region of Elongation,About 1 cm from root tip Cells become several times their original length. Vacuoles merge and form 90% of the mature cell,Stern -
13、Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region of Maturation,Sometimes called “region of differentiation” or “root-hair zone” Most cells differentiate into various distinctive cell types. Vascularization and development of root hairs,Stern - Introductory Pla
14、nt Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region of maturationRoot hairs,Absorb water and minerals and adhere tightly to soil particles. Grass plant 2ft3 soil, 15 x 106 roots has 14 x 109 root hairs Root surface area volleyball court Root hair surface area football field Root
15、 hairs function for 2 days to 3 weeks,Tuberous extensions of specialized epidermal cells,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region of MaturationCortex cells,Cortex cells mostly store food Between epidermis and inner tissues. Has endodermis as in
16、ner boundary (single layer cells) Cell walls impregnated with suberin bands; Casparian Strips. Forces all water and dissolved substances entering and leaving the central core to pass through plasma membranes of the endodermal cells.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved -
17、 McGraw Hill Companies,Region of MaturationCortex cells,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Region of Maturation,Vascular Cylinder lies at the inside of the endodermis. (xylem/phloem),Stern - Introductory Plant Biology: 9th Ed. - All Rights Reser
18、ved - McGraw Hill Companies,Development of Secondary Roots,Pericycle lies directly against the inner boundary of the endodermis. Lateral (branch) Roots develop,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,What structure within the root is responsible for
19、forming secondary or lateral roots?,A. Casparian strip B. Vascular cambium C. Cork cambium D. Pericycle E. Endodermis,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Specialized Roots,Food Storage Roots Sweet Potatoes Yams,Store starch, carbohydrates,Stern -
20、 Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Carrots, beets, turnips, radishes are food-storage tissues that are a combination of root and stem,Specialized Roots,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Water Stor
21、age Roots Pumpkin Family Propagative Roots Adventitious Buds develop into suckers. Fruit Trees,Specialized Roots,Manroot (Marah),Sisal,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Specialized Roots,Pneumatophores Spongy roots that extend above the waters
22、surface and enhance gas exchange between the atmosphere and subsurface roots.,Mangroves,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Aerial Roots-can absorb water from the air; has a thick epidermis to reduce water loss Orchids Banyan trees,Specialized Ro
23、ots,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Specialized Roots,Contractile Roots Pull plant deeper into the soil. Lilly Bulbs. Buttress Roots Stability - Tropical Trees.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill C
24、ompanies,Mycorrhizaefungi,Mycorrhizae form a mutualistic association with plant roots. (found in3/4 of all seed plants) Fungus is able to absorb and concentrate phosphorus much better than it can be absorbed by the root hairs.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGra
25、w Hill Companies,Mycorrhizaefungi,Mucorrhizal arbuscule inside a plant cell,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Root Nodules,Few species of bacteria (Rhizobium) produce enzymes that can convert nitrogen into nitrates and other nitrogenous substan
26、ces readily absorbed by roots. Legume Family (Fabaceae) Root nodules contain large numbers of nitrogen-fixing bacteria.,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Root Nodules,Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies,Review,Root Development Root Structure Specialized Roots Mycorrhizae Root Nodules,
