Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
GB
Uploaded bygohil sanjay bhagvanji
PPTX, PDF36,058 views

Theory of shoot apical meristem

The document discusses various theories related to shoot apical meristem, highlighting its role as a self-organizing center in plants that generates new cells and tissues. Key theories include the Apical Cell Theory, which posits a single apical cell as the controlling unit, the Histogenic Layer Theory detailing three histogenic layers in angiosperms, and the Anneu Initial and Meristem d'Attente Theory, which identifies different regions within the apical meristem. The document references relevant textbooks and online resources for further reading.

Education◦
Downloaded 169 times
Theories Of Shoot Apical Meristem Presented by : Panchal Rita C. M.sc Sem : 2 Roll no. 205 CBO: 405 Department Of life Sciences, H.N.G.U. Patan
 Content • Introduction • Apical cell Theory • Histogenic layer Theory • Anneu initial & meristem d'attente Theory
 Introduction • The shoot apical meristem is the terminal meristem of the shoot which is the continuing embryonic region of the plant. • It continuously gives rise to new cells and tissues from which new organs are formed. • It is self determining and autonomous organising centre of the plant.
• Apical Cell Theory • Presence of a single tetrahedral apical cell in the shoot apex of most vascular Cryptogams prompted Nageli (1878) to postulate the apical cell theory. • According to this theory a single apical cell is the structural and functional unit of apical meristem and it governs the whole process of growth.
• Such a single apical cell occurs in algae and majority of bryophytes and pteridophytes. • A single apical cell was also believed to be present in seed plants.
 Histogenic layer Theory • According to Dermen (1947) the terms tunica and corpus do not have fixed values and they fall short of having real meaning histogenetically. • He recognized three basic histogenic layers in all angiospermic Plants which were referred to as L -1 , L-2 and L-3 layers.
• These layers exist in various combinations of ploidy in the shoot apices. • For example the cells of L-1 may be 2x, to those of L- 2-2x and those of L-3-4x. • Expressed in terms of ploidy the Constitution would be 2,2,4.
• The epidermis of the stem and leaves is derived from L-1. The L-2 layer forms L-3 layered hypodermic of stems in some cases inner cortical tissues are also derived from it and in still others it may contribute to a portion of vascular tissue. • In general the vascular tissue and pith originate from L-3 layer.
 Anneu Initial and Meristem d'attente Theory • Buvat (1955) proposed that peripheral and subterminal regions are real initiating zones wheres distal zones are inert in nature. • He recognised three distinct regions in apical meristem. 1. The anneu ( the peripheral active zone) 2. The meristem d'attente ( the waiting meristem which becomes active only during formation of terminal flower or inflorescence)
3. The meristem medullary ( the central pith region) • Meristem d'attente consists of two parts the promeristeme sporogene and promeristeme receptaculair which thus contain part of tunica (except anneu Initial) and part of corpus ( except meristem medullary) • This Theory becomes Controversial Mainly because it consides meristem d’attente as waiting meristem which were priviously regarded as apical initial.
• References • A Text book of botany plant anatomy and economic botany volume -3 : by – S.N.Pandey A. Chadha • Text book of Botany Angiosperms by: B.P.Pandey https://en.m.wikipedia.org https://www.slideshare.net
Thank You