Untitled Document
Contact Us    |   Register
SITE SEARCH
HOME
ONLINE COMMUNITY
MEMBERSHIP
MEETINGS & EVENTS
PUBLICATIONS/RESOURCES
CAREERS
GOVERNANCE
SECTIONS
AWARDS & FUNDING
EDUCATION & RESEARCH
PUBLIC AFFAIRS
EDUCATION FOUNDATION
ABOUT US


seo services

garcinia cambogia extract

cash loans

Chapter 22

Responses to
Abiotic Stresses

 

Abiotic stresses are prevalent in nature and can substantially diminish plant yields. Plant responses to stressful environmental factors can be part of the mechanisms that permit the plant to withstand the stress. Alternatively, such responses may be a manifestation of injury that has occurred in response to the stress. The response depends on the severity and duration of the stress, the developmental stage of the affected plant, the tissue type, and the interactions of multiple stresses. Mechanisms that permit stress survival are termed resistance mechanisms and can allow an organism to avoid or tolerate stress. Acclimation, a process that improves stress resistance, may occur in response to a mild non-lethal stress. Changes in gene expression may be involved in the mechanism of stress resistance or may be a result of injury. Described in this chapter are the abiotic stresses arising from drought, salinity, low temperature, flooding, air pollution, and high temperature.
      Stresses involving water deficit may arise from drought conditions, saline soils, or low temperature. To quantify the effect of this stress on the plant, one can determine the water status of the plant by using either or RWC. Measuring the water status of the plant is important for determining the impact of the environmental condition. Decreases in plant water potential may be brought about by osmotic adjustment, the accumulation of compatible solutes that promote acclimation to dry or saline soils. Compatible solutes, such as glycine betaine, mannitol, pinitol, and proline, do not disrupt cellular function when accumulated to high concentrations in the cytoplasm. In addition to osmotic adjustment, some compatible solutes may serve other protective functions. Effects of water deficit and perturbing ions on the membrane may be minimized by the action of carriers, pumps, and channels. Amelioration of plant stress may also arise from the function of a set of genes discovered during investigation of the desiccation stages of seed development. Five groups of Lea genes have been identified, based on homology among different species. The majority of these proteins are hydrophilic and soluble when boiled; however, not all groups have these characteristics. Several LEA-encoding genes have been shown to function in stress resistance by using overexpression technology in transgenic plants or yeast. Various other types of genes also are induced by water deficit, including those that may protect the plant from secondary biotic stresses. Osmotin, a tobacco protein with antifungal activity, accumulates during water deficit. The mechanisms of gene induction are regulated by specific DNA elements: Two classes of elements, ABRE and DRE, have been found in many water-deficit–induced genes.
      Flooding causes an oxygen deficit in the cell that impacts respiratory metabolism. The ability to tolerate flooding varies greatly among species and can be altered by acclimation processes involving exposure to hypoxic conditions (3 kPa oxygen). During short-term acclimation to anoxic conditions, plants generate ATP through glycolysis and fermentation; this shift from aerobic metabolism to glycolytic fermentation involves changes in gene expression. The plant hormone ethylene promotes long-term acclimative responses, including formation of aerenchyma and stem elongation. Some wetland genotypes are adapted to long-term flooding.
      Oxidative stress may arise from any abiotic or biotic stress that causes the formation of a ROS, such as hydrogen peroxide (H2O2), superoxide anion (O2•–), and hydroxyl radical (HO ), or perhydroxyl radical (HO2). Plants scavenge and eliminate these reactive molecules by using antioxidant defense systems—antioxidants and antioxidant enzymes— that are present in various subcellular compartments. Ozone exposure to plants can be used as a model system to determine how ROS cause oxidative damage to biomolecules. Studies in which antioxidant enzymes are overexpressed in transgenic plants have emphasized the important role of subcellular compartmentation in detoxification mechanisms; that is, overexpression of antioxidant enzymes in one compartment may not improve stress tolerance if oxidant-scavenging mechanisms are limiting in other cellular compartments.
      Heat stress responses are widely conserved among different organisms. Thermotolerance can be developed as plants acclimate to a nonlethal high temperature. During heat stress in plants, as in other organisms, gene expression patterns, including transcription and translation, are altered to promote the accumulation of HSPs. The five major classes of HSPs, defined according to size, are conserved among different organisms. In general, the HSPs function as chaperones to promote proper folding of proteins. Expression of HSPs is controlled by a transcription factor that recognizes a conserved DNA element, 5’-nGAAn-3’, present in multiple copies in the promoter. The transcription factor is active as a trimer and must be derepressed to activate gene expression.
      Progress in understanding plant responses to stress has been impressive. Nonetheless, numerous important questions remain. None of the mechanisms by which higher plants perceive abiotic stresses has been elucidated. Progress in this crucial area will advance substantially our knowledge of stress-initiated signal transduction events. Stress-related signals are propagated by several different agents. In some cases, these signal transduction events involve at least one of the five best-studied plant hormones: ABA, auxins, cytokinins, ethylene, and gibberellins. Calcium is implicated as a second messenger in many stress responses. However, perhaps signaling molecules not yet identified also participate in controlling plant responses to the environment. As plant genomes are analyzed, it has become apparent that many genes associated with mammalian signal transduction cascades, including peptide hormones and membrane receptor kinases, also are present in plants.


© Copyright American Society of Plant Biologists 2013 (All Rights Reserved)


Debugging Information
ColdFusion Server Enterprise 9,0,1,274733
Template /publications/biotext/sumrys/ch22.cfm
Time Stamp 08-Feb-16 01:39 PM
Locale English (US)
User Agent CCBot/2.0 (http://commoncrawl.org/faq/)
Remote IP 54.167.40.25
Host Name 54.167.40.25


Execution Time

Total Time Avg Time Count Template
232 ms 232 ms 1 top level C:\home\dev.aspb.org\www.aspb.org\publications\biotext\sumrys\ch22.cfm
227 ms 227 ms 1 C:/home/dev.aspb.org/www.aspb.org/includes/header.cfm
107 ms 107 ms 1 C:/home/dev.aspb.org/www.aspb.org/Application.cfm
0 ms 0 ms 1 C:/home/dev.aspb.org/www.aspb.org/includes/aspbtop2.cfm
0 ms 0 ms 1 C:/home/dev.aspb.org/www.aspb.org/includes/footer.cfm
3 ms  STARTUP, PARSING, COMPILING, LOADING, & SHUTDOWN
342 ms  TOTAL EXECUTION TIME
red = over 250 ms average execution time


SQL Queries

GetGlobalSettings (Datasource=ASPBAwards, Time=22ms, Records=1) in C:\home\dev.aspb.org\www.aspb.org\Application.cfm @ 13:39:57.057
	SELECT
       [MeetingLocation]
      ,[MeetingURL]
      ,[MeetingDates]
  FROM [dbo].[GlobalSettings]


Scope Variables

Application Variables:
applicationname=aspb_web
awardsadminemail=slee@aspb.org
awardsadminfax=
awardsadminname=Sylvia Lee
awardsadminphone=301-251-0560 x114
awardsadmintitle=Executive and Governance Affairs Administrator
awardsappyear=2016
awardsdeadline=02/15/2016
awardsenddate=Monday, February 15, 2016 (11:59 p.m. ET)
awardsnextyear=2017
awardsnotifydate=March 21, 2016
awardsstartdate=Monday, January 04, 2016
awardstitle=Call for 2016 Nominations for ASPB Awards
awardsyear=2016
bloomeadminemail=katie@aspb.org
bloomeadminfax=301-251-0560
bloomeadminname=Katie Engen
bloomeadminphone=301-251-0560
bloomeadmintitle=ASPB Education Coordinator
bloomedeadline=04/15/2015
bloomeenddate=Wednesday, April 15, 2015 (11:59 p.m. ET)
bloomenextyear=
bloomenotifydate=_ 
bloomestartdate=Tuesday, February 03, 2015
bloometitle=Plant BLOOME 2015
bloomeyear=2015
excomadminemail=slee@aspb.org
excomadminfax=301-251-0560
excomadminname=Sylvia Lee
excomadminphone=301-251-0560 x114
excomadmintitle=Executive and Governance Affairs Administrator
excomballotdeadline=05/29/2015
excomballotenddate=Friday, May 29, 2015 (11:59 p.m. ET)
excomballotnotifydate=06/10/2015
excomballotstartdate=Thursday, April 23, 2015
excomballottitle=ASPB Official 2015 Election Ballot
excomlastyear=2014
excommode=Nominate
excomnextyear=2016
excomnominatedeadline=02/16/2015
excomnominateenddate=Monday, February 16, 2015 (11:59 p.m. ET)
excomnominatenotifydate=mid-March, 2015
excomnominatestartdate=Friday, December 12, 2014
excomnominatetitle=ASPB Call for Executive Committee Nominations 2015
excomyear=2015
highwireadminemail=lpalmer@aspb.org
highwireadminname=Linda Palmer
hosthead=dev.aspb.org
journalaccessadminemail=katie@aspb.org
journalaccessadminfax=301-296-0902
journalaccessadminname=Katie Engen
journalaccessadminphone=301-296-0902
journalaccessadmintitle=ASPB Education Coordinator
journalaccessdeadline=02/13/2013
journalaccessenddate=Tuesday, February 12, 2013 (11:59 p.m. ET)
journalaccessnextyear=2014
journalaccessnotifydate=late-April, 2013
journalaccessstartdate=Thursday, September 27, 2012
journalaccesstitle=ASPB Journals - Online Access Nomination Form
journalaccessyear=2014
meetingdates=July 9-13, 2016
meetinglocation=Austin, Texas
meetingurl=http://my.aspb.org/?page=ME_Index
mepadminemail=katie@aspb.org
mepadminfax=301-296-0902
mepadminname=Katie Engen
mepadminphone=301-296-0903
mepadmintitle=ASPB Education Coordinator
mepdeadline=10/31/2014
mependdate=Friday, October 31, 2014 (11:59 p.m. ET)
mepnextyear=2015
mepnotifydate=November 21, 2014
mepstartdate=Monday, August 18, 2014
meptitle=ASPB Master Educator Program (MEP)
mepyear=2014
newshead=newsletter.aspb.org
pgcb=
physloc=c:\home\dev.aspb.org\wwwroot
rtaadminemail=slee@aspb.org
rtaadminfax=301-279-2996
rtaadminname=Sylvia Lee
rtaadminphone=301-251-0560 x114
rtaadmintitle=Executive and Governance Affairs Administrator
rtadeadline=03/04/2016
rtaenddate=Friday, March 04, 2016 (11:59 p.m. ET)
rtanextyear=
rtanotifydate=mid-April, 2016
rtastartdate=Monday, October 26, 2015
rtatitle=ASPB Minority Affairs Committee 2015 Recognition Travel Award Applications
rtayear=2016
showrightrail=true
surfadminemail=katie@aspb.org
surfadminfax=301-279-2996
surfadminname=Katie Engen
surfadminphone=301-251-0560 x114
surfadmintitle=ASPB Education Coordinator
surfdeadline=02/11/2015
surfenddate=Wednesday, February 11, 2015 (11:59 p.m. ET)
surfnextyear=2016
surfnotifydate=mid-April, 2015
surfstartdate=Tuesday, December 01, 2015
surftitle=2015 Summer Undergraduate Research Fellowship Awards
surfyear=2015
travelgrantsabstractdate=February 16, 2015
travelgrantsabstractfee=$25
travelgrantsadminemail=slee@aspb.org
travelgrantsadminname=Sylvia Lee
travelgrantsadminphone=301-251-0560 x114
travelgrantsadmintitle=Executive and Governance Affairs Administrator
travelgrantsdeadline=01/12/2015
travelgrantsenddate=Monday, January 12, 2015 (11:59 p.m. EDT)
travelgrantsfeewaived=$200
travelgrantsgrantamount=$575
travelgrantsgranttotal=
travelgrantsnextyear=2016
travelgrantsnotifydate=Tuesday, February 10, 2015
travelgrantsstartdate=Monday, November 03, 2014
travelgrantstitle=ASPB 2015 Travel Grants Award Application
travelgrantstotalamount=$46,000
travelgrantswaived=
travelgrantsyear=2015
wyitaabstractfee=$50
wyitaadminemail=slee@aspb.org
wyitaadminname=Sylvia Lee
wyitaadminphone=301-251-0560 x114
wyitaadmintitle=Executive and Governance Affairs Administrator
wyitaappyear=2015
wyitadeadline=01/13/2015
wyitaenddate=Tuesday, January 13, 2015 (11:59 p.m. ET)
wyitafeewaived=$165
wyitagrantamount=$1000
wyitagranttotal=$7000
wyitanextyear=2016
wyitanotifydate=February 10, 2015
wyitastartdate=Monday, November 03, 2014
wyitatitle=ASPB 2015 Women's Young Investigator Travel Award Applications
wyitawaived=
wyitayear=2015
ymhosthead=my.aspb.org
CGI Variables:
AUTH_PASSWORD=
AUTH_TYPE=
AUTH_USER=
CERT_COOKIE=
CERT_FLAGS=
CERT_ISSUER=
CERT_KEYSIZE=
CERT_SECRETKEYSIZE=
CERT_SERIALNUMBER=
CERT_SERVER_ISSUER=
CERT_SERVER_SUBJECT=
CERT_SUBJECT=
CF_TEMPLATE_PATH=C:\home\dev.aspb.org\www.aspb.org\publications\biotext\sumrys\ch22.cfm
CONTENT_LENGTH=
CONTENT_TYPE=
CONTEXT_PATH=
GATEWAY_INTERFACE=CGI/1.1
HTTPS=off
HTTPS_KEYSIZE=
HTTPS_SECRETKEYSIZE=
HTTPS_SERVER_ISSUER=
HTTPS_SERVER_SUBJECT=
HTTP_ACCEPT=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
HTTP_ACCEPT_ENCODING=x-gzip, gzip, deflate
HTTP_ACCEPT_LANGUAGE=en-us,en-gb,en;q=0.7,*;q=0.3
HTTP_CONNECTION=
HTTP_COOKIE=
HTTP_HOST=www.aspb.org
HTTP_REFERER=
HTTP_USER_AGENT=CCBot/2.0 (http://commoncrawl.org/faq/)
PATH_INFO=/publications/biotext/sumrys/ch22.cfm
PATH_TRANSLATED=C:\home\dev.aspb.org\www.aspb.org\publications\biotext\sumrys\ch22.cfm
QUERY_STRING=
REMOTE_ADDR=54.167.40.25
REMOTE_HOST=54.167.40.25
REMOTE_USER=
REQUEST_METHOD=GET
SCRIPT_NAME=/publications/biotext/sumrys/ch22.cfm
SERVER_NAME=www.aspb.org
SERVER_PORT=80
SERVER_PORT_SECURE=0
SERVER_PROTOCOL=HTTP/1.0
SERVER_SOFTWARE=Microsoft-IIS/7.5
WEB_SERVER_API=
Client Variables:
cfid=1867498
cftoken=7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
hitcount=1
lastvisit={ts '2016-02-08 13:39:57'}
timecreated={ts '2016-02-08 13:39:57'}
urltoken=CFID=1867498&CFTOKEN=7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
Cookie Variables:
CFID=1867498
CFTOKEN=7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
Server Variables:
coldfusion=Struct (8)
os=Struct (5)
Session Variables:
address1=
address2=
cfid=1867498
cftoken=7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
city=
constituentid=
cookie=
country=
email=
fax=
firstname=
gender=
id=
institution=
lastname=
memberemail=
memberid=
membername=
membership=
membertype=
middlename=
pgcb=ok
phone=
prefix=
sessionid=ASPB_WEB_1867498_7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
state=
suffix=
title=
urltoken=CFID=1867498&CFTOKEN=7adc15aa4bde96a-95C60DBF-CC90-1021-0EA4382263A47848
websiteid=
ymsessionid=
zip=
URL Parameters:
COOKIE=
Debug Rendering Time: 62 ms