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 20

Senescence and
Programmed Cell Death

 

Selective death of cells, tissues, and organs is an essential feature of plant development and survival. The term programmed cell death refers to any process by which protoplasm, with or without the cell wall that encloses it, is eliminated as part of a developmental or adaptive event in the life cycle of the plant. Plants dispose of unwanted cytoplasm or whole cells by several mechanisms, including self-ingestion (autophagy), lysis (lysigeny), or a kind of mummification (as seen in endosperm formation). PCD is essential for normal reproductive and vegetative development and for responses to environmental stresses. During senescence (a PCD-like process associated with the terminal stages of organ development), specific genes are expressed, some of which have been cloned and their promoters analyzed. Stay-green mutants are genetic variants in which expression of senescence-associated genes is impaired.
      Senescing cells are metabolically active. The chlorophyll degradation pathway is turned on, accompanied by the unmasking or accumulation of carotenoids and other pigments. Proteins are broken down, and the mobilized organic nitrogen and organic sulfur are exported from senescing leaves. Catabolism of nucleic acids releases inorganic phosphate. Photosynthesis declines, and peroxisomes are redifferentiated into glyoxysomes, which convert lipids to sugars. Metabolic regulation during senescence involves responses to cellular redox conditions, compartmentation, and differential susceptibility of enzymes to proteolysis. Senescence is sensitive to growth regulators, particularly to the senescence-promoter ethylene and to cytokinins, which act as senescence antagonists.
      Senescence is used both as part of adaptive strategies that ensure seasonal survival and as a tactic deployed when an unpredictable stress is experienced. Formation of TE and mobilization of cereal endosperm are examples of developmental PCD. Zinnia leaf mesophyll cells induced to form TE in culture are a valuable model of cell death. Several different pathways lead to death of starchy endosperm and aleurone cells in cereals. Ethylene can induce PCD in starchy endosperm cells, and GA and ABA regulate cell death in cereal aleurone. An example of PCD under an abiotic environmental stress is aerenchyma formation, which is a response to limited oxygen availability, such as when roots are flooded. Ethylene mediates aerenchyma formation, and signaling between ethylene production and hypoxia sensing is mediated by calcium.
      The hypersensitive response is an example of PCD related to biotic stress and has its own effect on the programmed nature of cell death. Lesion-mimic mutants are useful models for analyzing HR. Such mutations in Arabidopsis fall into two groups: those that trigger defense responses, and those that do not. Lesion-mimic mutants primarily affect cell death in the context of the defense response to pathogens but apparently have no effect on other events in developmental cell death. Reactive oxygen intermediates are a key trigger in PCD accompanying the HR. HR can be compared with apoptosis, a type of PCD in animals that has been intensively researched and has been an influential general model for PCD and its regulation. Future directions for PCD research include the relationship between programmed cellular processes and whole-organism aging.


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


Debugging Information
ColdFusion Server Enterprise 9,0,1,274733
Template /publications/biotext/sumrys/ch20.cfm
Time Stamp 05-Feb-16 07:07 PM
Locale English (US)
User Agent CCBot/2.0 (http://commoncrawl.org/faq/)
Remote IP 184.72.177.182
Host Name 184.72.177.182


Execution Time

Total Time Avg Time Count Template
227 ms 227 ms 1 top level C:\home\dev.aspb.org\www.aspb.org\publications\biotext\sumrys\ch20.cfm
224 ms 224 ms 1 C:/home/dev.aspb.org/www.aspb.org/includes/header.cfm
94 ms 94 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
4 ms  STARTUP, PARSING, COMPILING, LOADING, & SHUTDOWN
325 ms  TOTAL EXECUTION TIME
red = over 250 ms average execution time


SQL Queries

GetGlobalSettings (Datasource=ASPBAwards, Time=17ms, Records=1) in C:\home\dev.aspb.org\www.aspb.org\Application.cfm @ 19:07:03.003
	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\ch20.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/ch20.cfm
PATH_TRANSLATED=C:\home\dev.aspb.org\www.aspb.org\publications\biotext\sumrys\ch20.cfm
QUERY_STRING=
REMOTE_ADDR=184.72.177.182
REMOTE_HOST=184.72.177.182
REMOTE_USER=
REQUEST_METHOD=GET
SCRIPT_NAME=/publications/biotext/sumrys/ch20.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=1862678
cftoken=6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
hitcount=1
lastvisit={ts '2016-02-05 19:07:03'}
timecreated={ts '2016-02-05 19:07:03'}
urltoken=CFID=1862678&CFTOKEN=6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
Cookie Variables:
CFID=1862678
CFTOKEN=6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
Server Variables:
coldfusion=Struct (8)
os=Struct (5)
Session Variables:
address1=
address2=
cfid=1862678
cftoken=6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
city=
constituentid=
cookie=
country=
email=
fax=
firstname=
gender=
id=
institution=
lastname=
memberemail=
memberid=
membername=
membership=
membertype=
middlename=
pgcb=ok
phone=
prefix=
sessionid=ASPB_WEB_1862678_6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
state=
suffix=
title=
urltoken=CFID=1862678&CFTOKEN=6aa81da3381bf736-070335B2-98DA-EEB2-32E420D43DA56D3D
websiteid=
ymsessionid=
zip=
URL Parameters:
COOKIE=
Debug Rendering Time: 66 ms