How many number of mango trees are flowering in your place?
Kerala shows high percentage of flowering than delhi ?
What are the common mango varieties are there in your area ?
What are the factors responsible for flowering?
1)external clues : Temperature,Day length
2)Internal clues: Hormone ??
Many more !?
@Prithviraj CUBE had an interesting story to tell us ;
there is a mango tree with one branch having flowers and another branch without flowers?
Why that ?what cause branch A to not flower?
How does a plant change from a Vegetative meristem to floral meristem?
Do we have problems in understanding terms like differentiation, meristem !? Yes.we have
How shoot apical meristem gives rise to stem ,leaf , Trichome (shoot hair )?
Are there any hormone are required?
shoot apical meristem(SAM) have any ability to synthesis Auxin !?
How auxin is synthesized in SAM? @Prithviraj CUBE
Auxin is derived from *tryptophan ( sorry I mentioned in Chatshaala that methionine as a precursor for auxin ,but methionine is a precursor for ethylene).
How tryptophan is synthesized by plants?
During the course of their life cycles, plants undergo various morphological and physiological changes un- derlying juvenile-to-adult and adult-to-flowering phase transitions. To flower or not to flower is a key step of plasticity of a plant toward the start of its new life cycle.https://www.researchgate.net/publication/273131527_To_Bloom_or_Not_to_Bloom_Role_of_MicroRNAs_in_Plant_Flowering
CUBE context to Curriculum WhatsApp group
[14/01, 10:19 am] Arunan sir: Very interesting insights from Simple Mango Tree Mapping.
What can be the difference between Vegetative Meristem and Floral Meristem?
[14/01, 10:55 am] Himanshu Joshi: Tree growth is driven by leaf primordium initiation at shoot apices through a series of growth and developmental events largely mediated hormonally and often determinate in nature. This repeating pattern keeps trees alive and reproductive and conserves the phenotype.
[14/01, 11:12 am] Himanshu Joshi: auxin is indole acetic acid (abbreviated IAA), a weak organic acid with a structure similar to the amino acid tryptophan.
It controls cell division, cell expansion, and cell differentiation. It has a ubiquitous and context-dependent function, making it difficult to assign a single function to auxin.
It appears that auxin affects almost all developmental steps in plants from early embryogenesis to fruit ripening and controls organogenesis at the meristems, which define plant architecture. Nowadays, research focuses on understanding how such a small molecule can be ubiquitous and at the same time have context-dependent function.
Sounds like context to the curriculum
Questions came in yesterday’s Chatshaala
How does SAM ( shoot apical meristem)synthesis Auxin?
Auxin is formed from a precursor Tryptophan.
Tryptophan biosynthesis pathway begins with phosphoenol pyruvate ( intermediate of glycolysis)>Shikimate >Anthranilate > Chorismate and follow the flowchart
How does auxin help in shoot formation?
Early stage of adventitious shoot formation. Auxin is transferred from the apical to the basal region of the internodal segment by PIN auxin efflux carriers, which maintain low endogenous auxin levels on the apical side, facilitating differentiation of adventitious shoots. Auxin accumulates on the basal side of the internodal segment, where it suppresses adventitious shoot formation and induces callus formation.
b) Late stage of adventitious shoot formation.
One of the shoots formed becomes dominant. Auxin from its apical meristem is transported into the internodal segment, and the auxin transport stream suppresses growth of other shoots.
Where in SAM( shoot apical meristem) the stemcell present?
Wus plays a key stem-cell-promoting role, which therefore
also makes it a likely target of pathways involved in terminating stem cell maintenance in floral meristems
The stem cells in the shoot apical meristem (SAM) are
located in the L1–L3 layers at the meristem centre, and
their progeny are progressively displaced towards the periphery of the meristem where they are recruited
into organ primordia.(leaf primordia & flower primordia ,i guess)
Vegetative meristem formation
WUS and CLV3, whereby WUS promotes the expression of
CLV3 which in turn* , via activation of the Clv complex-
dependent signalling pathway, restricts WUS expression
Floral meristem formation
Two groups have now shown that AGAMOUS (AG), a gene
previously known to play a dual role in floral organ patterning and the termination of flower development, interacts
with WUS .
Moreover, when WUS
expression was forced by expression under control of either
the LEAFY (LFY) or APETALA3 (AP3)  or AG promoters , supernumerary stamens and carpels as well as
homeotic transformations were observed.
(Actually LFY,AP3,AG all are floral genes)
Transition from Vegetative growth to reproductive growth https://www.cell.com/fulltext/S0960-9822(01)00471-7
[14/01, 1:00 pm] Prithviraj CUBE: Give details of florigen formation and function also.
[14/01, 1:28 pm] Vijaya tilak : What is WUS expression Theertha.
Thank you for informative tutorial🙏
Recent advances in molecular genetics in plants revealed the molecular nature of florigen as a globular protein named FT.These prerequisites were determined from the long history of classical physiological studies, and they are as follows: (1) produced in leaves under a favorable day length, (2) transported from leaves to the SAM through phloem, and (3) conserved across angiosperms .
Florigen is a mobile flowering signal in plants that has a strong impact on plant reproduction and is considered one of the important targets for crop improvement. At the molecular level, *florigen is represented as a protein product encoded by the FLOWERING LOCUS T (FT) gene, which is highly conserved across flowering plants and thus the understanding of this protein is expected to be applied to the improvement of many crops.
WUSCHEL (WUS) is a transcription factor,which means a protein that formed from WUS gene that can promote the production of protein CLV3)& there by helping in vegetative growth. This is what I understood. Let’s read this paper too.
The maintenance of the stem cell niche in the shoot apical meristem, the structure that generates all of the aerial organs of the plant, relies on a canonical *feedback loop between WUSCHEL (WUS) and CLAVATA3 (CLV3). *WUS is a homeodomain transcription factor (a protein produced from WUS gene, i think ) expressed in the organizing centre that moves to the central zone to promote stem cell fate. CLV3 is a peptide whose expression is induced by WUS in the central zone and that can move back to the organizing centre to inhibit WUS expression.
Question arises in yesterday’s Chatshaala
1)what is a meristem!?
Meristems are clusters of cells that allow the basic body pattern established during embryogenesis to be reiterated and extended after germination.
Meristematic cells are similar to stem cells in animals.
Meristems fall into three categories: apical lateral, and intercalary.
Apical meristem:Shoot & Root
The shoot apical meristem produces stems, leaves, and reproductive structures.
Vegetative Growth - Developmental Biology - NCBI Bookshelf.
The root stem cell niche resides within quiescent centre (QC)
The shoot stem cell is in Organizing centre (OC).
(A) In the Arabidopsis root, stem cells for all cell types surround the quiescent center (QC), a small group of organizer cells that are required for stem cell maintenance. Stem cells undergo asymmetric cell divisions and their daughter cells differentiate into all root cell types. Root stem cells and quiescent cells are specified by a combination of the PLETHORA (PLT1 and PLT2), SHORTROOT (SHR), and SCARECROW (SCR) transcription factors.(responsible for root parts formation ,I think )Black arrows define a stem cell maintenance signal produced by quiescent cells that has yet to be identified.
(B) In the shoot of Arabidopsis, a stem cell pool is located above the organizer cells (OC), (also called Organizing centre)which express the WUSCHEL (WUS) transcription factor. The black arrow indicates an unknown signal that induces the organizer cells to express WUS. Stem cells of the plant shoot produce the small secreted protein CLAVATA3 (CLV3) that negatively regulates expression of WUS (green arrows). Stem cell daughters that leave the signaling domain differentiate and form leaf primordia (LP).