May 4, 2018 | Author: mailtosiba | Category: Tissue (Biology), Bark, Root, Plant Stem, Morphology (Biology)
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Biology course notes at school level...


Chapter 31


There are about 262,000 species of plants. About 235,000 species or 90%, are angiosperms. Angiosperms can be either herbaceous or oo!". #erbaceous plants can be annuals, biennials an! perennials. $oo!" plants are perennials.

THE PLANT BODY The plant bo!" consists of a root system an! a shoot system. The shoot s"stem consists of a stem that bears leaes, floers, fruits an! sometimes ade!t"t"o#s roots. &lants are ma!e of cells organi'e! into tissues an! organs. (oots, stems, floers an! fruits are organs. There are three tissue s"stems that e)ten! throughout the entire bo!" of the plant. *ach tissue s"stem contains to or more tissues, hich can be simple or comple) !epen!ing on the +in!s of cells that form the tissue. A groing plant cell secretes a $r"mary %e&& 'a&& that stretches as the cell increases in si'e. The se%o!dary %e&& 'a&& is !eposite! after the cell stops groing. CELL TYPES Pare!%hyma %e&&s • • • •

iing cells at maturit". maturit". #ae thin primar" alls. -unction in storage, secretion an! photos"nthesis. photos"nthesis. -oun! throughout the bo!" of the plant.

Co&&e!%hyma %e&&s • • • •

iing cells at maturit". maturit". #ae uneenl" thic+ene! primar" cell alls. -unction in support in fle)ible parts of the plant. -oun! in petioles, leaf eins an! other parts of the plant that must be fle)ible.

S%&ere!%hyma %e&&s • •

#ae both primar" an! thic+ene! secon!ar" cell alls. Cells are often !ea! at maturit".

• •

econ!ar" all ith pits. &roi!e structural support.

There are to t"pes of sclerench"ma sclerench"ma cells/ s%&ere"ds an! (")ers. • • • •

• • • • •

S%&ere"ds ma" be liing or !ea! at maturit". hort, cubical cells. clerei! rich tissue ma" be har! an! infle)ible. -orm part of the shell an! pits of fruits, e.g. coconuts, alnuts, cherries, etc. F")ers are often !ea! at maturit". ong, tapere! cells often in clumps. #ae fe pits in their secon!ar" all. &roi!e strength an! elasticit". -oun! throughout the plant bo!", common in stems an! some leaes.

Tra%he"ds • • • • •

ea! at maturit". ong an! tapere! cells. #ae secon!ar" alls e)cept at pits. &its on lateral an! en! alls. Con!uction of ater an! minerals.

*esse& e&eme!ts • • • • •

ea! at maturit". ong an! c"lin!rical cells oine! en! to en!. econ!ar" cell all e)cept at pits. *n! alls hae perforations. Con!uction of ater an! minerals.

S"ee t#)e mem)ers • • • • • • •

iing cells at maturit". maturit". ac+ nucleus an! other organelles at maturit". maturit". *longate! cells, c"lin!rical, oine! en! to en!. econ!ar" cell all present. *n! alls are s"ee $&ates ith holes. C"toplasm e)ten!s from one cell to the ne)t through the holes of the siee plate. Con!uct the pro!ucts of photos"nthesis.

Com$a!"o! %e&&s • • • •

iing cells at maturit". maturit". Associate! to a siee tube member b" means of plasmo!esmata. Assists in moing sugars in an! out of siee tube members. The nucleus is thought to !irect the actiit" of both cells.


Compose! of three simple tissues. &arench"ma tissue Collench"ma tissue clerench"ma tissue

parench"ma cells Collench"ma cells sclerei!s, fibers


Compose! of to comple) tissues. "lem

Trachei!s essel elements &arench"ma cells -ibers


iee tube members Companion cells &arench"ma cells -ibers


Compose! of to comple) tissues. *pi!ermis

&arench"ma cells 4uar! cells Trichomes


Cor+ cells Cor+ cambium cells Cor+ parench"ma

Gro#!d t"ss#e performs man" functions/ •

&hotos"nthesis, &hotos"nthesis, storage, secretion, fle)ible an! rigi! structural support

&arench"ma cells hae thin primar" alls pol"he!ral cells function in photos"nthesis, storage an! secretion remain alie at maturit".

Collench"ma cells hae an uneenl" thic+ene! primar" all proi!e fle)ible structural support in soft nonoo!" organs cells elongate! remain alie at maturit".

clerench"ma cells hae primar" an! thic+ secon!ar" alls proi!e rigi! support to organs cells usuall" !ie at maturit" fibers are long an! tapere! sclerei!s are short an! cubical.

*as%#&ar t"ss#e system  con!ucts materials throughout the plant bo!" an! proi!es support. •

0y&em con!ucts ater an! minerals from the roots to all parts of the plant

trachei!s an! essel elements are the con!ucting cells an! are !ea! at maturit" both hae all pits for lateral transport.

Ph&oem transports sugars in solution to all plant parts

siee tube members are the con!ucting cells companion cells regulate the metabolism of the siee tube members

 both remain alie at maturit" maturit" siee tube members members lac+ nucleus an! other other organelles.

Derma& t"ss#e system is the outer protectie coering of herbaceous plants an! the "oung ten!er parts of oo!" plants. •

E$"derm"s usuall" consists of a single la"er of parench"ma cells ith 1#ard %e&&s an! tr"%homes secretes the a)" %#t"%&e gas e)change occurs through the stomata. 7t is ma!e of   parench"ma t"pe cells. Per"derm forms the outer bar+ of oo!" plants %or2 %e&&s are !ea! at maturit" an! fille! ith s#)er"!, a ater proof substance %or2 $are!%hyma functions as a storage tissue.

GROWTH 4roth in plants is locali'e! in regions calle! meristems. •

7t inoles cell !iision, cell elongation an! cell !ifferentiation.

1. Pr"mary 1ro'th causes the roots an! stems to elongate. • •

7t occurs in all plants. The apical meristem at the tip of roots an! stems is responsible.

2. Se%o!dary 1ro'th is an increase in stem an! root girth. • • •

7t occurs in oo!" plants onl". 7t is !ue to the actiit" of the lateral meristems/ ascular cambium an! cor+ cambium. ascular ascular cambium forms a c"lin!er along the length of roots an! stems, beteen the )"lem an!  phloem it pro!uces more more )"lem an! phloem. Cor+ cambium is locate! in the outer bar+.

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