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Basics of Plant Physiology

Basics of Plant Physiology

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Basics of Plant Physiology


· Two regions of the spectrum is effective photocybernetically blue to U.V. and red to near infrared.

· Phytochrome is photoconvertible that is it occurs in two forms i.e. P-660 and P-730.

· Based on the photoperiodic responses Garner and Allard have calassifeid the plants into 3 categories.
1. Short day 2. Long day 3. Day Neutral .

· Long day plants form only a compact rosette of leaves when grown on short days.

· Garner and Allard found that the amount of Vegetative growth is proportional to the duration of day light.

· Day light at the equator – 12 hrs.


· The tendency of substance to give up heat is called “Temperature”.

· Temperature is a qualitative term while heat is a quantitative term of radiant energy.

· The hottest spots on earth inhabitated by living organisms are called “Geysers”.

· Heat exchange between the plant and environment takes place in three ways.

1. Conduction and Convection (Sensible heat exchange).

2. Evaporation and condensation of water (Latent heat exchange).

3. Direct radiation.

· The different between solar (incoming) radiation and terrestrial (outgoing) radiation is called “Net radiation”.

· The process influenced must strongly by temperature include

i. Chemical reactions.

ii. Gas solubility.

iii. Mineral absorption.

iv. water uptake.

· The Viscosity of water doubles as temperature drops from 250C to 00C.

· Optimum absorption of water takes places above 300C.

· Each crop plant requires a certain number of effective heat units before it can mature called as “Thermal constant”.

· Thermal constant for Maize – 1600 – 1800 units.

Cotton – 1900 units.

· Plant zero for spring Wheat 2.80C.

Corn 12.80C.

Cotton 16.80C

· When temperature rise above the maximum for growth a plant enters a “Quiscent State”. When plant drop below the minimum for growth a plant enters “Dormant”.

· Classification based on heat resistant :

1. Heat sensitive – Tomato wilt virus (TWV).

2. Heat tolerant eukaryotes – Plants of sunny and dry habitats.

3. Heat tolerant prokaryotes – Bacteria, B.G.A.

· Classification based on cold – resistant.

1. Chilling sensitive – Rice, Cotton, Cowpea.

2. Freezing sensitive – Valancia, Peanuts.

3. Freezing tolerant – Certain fresh water algae.

· 73% of earth’s surface is covered with water.

· According to Hutchinson world precipitation amounts to about 4.46 X 1020 ga. Falls on land, 3.47 X 1020 ga falls on ocean.

· White crystals of frozen water – snow.

· A special type of pecipitation during the summer season in the from of small ice pieces Hail.

· Frozen (or) partly frozen rain is called “Sleet”.

· Visibles vapor content of the atmosphere – Fog & Mist.

· The moisture condensed upon the surfaces of cool bodies like grasses, usually at night is called “Dew”. It is the main source of “Ephemeral plants”.

· Based on the rainfall India is divided into 4 climatic regions.

1. Wet zone – rainfall exceeding 200 cm.

Natural vegetation – Evergreen and Semi evergreen forests.

2. Intermediate zone – 100 – 200 cm NV – Deciduous forests

3. Dry zone – 50 -100 cm NV – Thorny dry deciders and Semi desert.

4. Arid zone – < 50 cm N.V. – Thorny forests with large areas of desert and semi desert.

· Based on the adaptation of plants to water factor warming.

· Proposed 3 ecological groups viz., Hydrophytes, Mesophyte, Xerophytes.

· In hydrophytes extensive development of “aeren chyma”.

· Mesophytes Exhibit temporary willing at noon time.

· Homihydric plants : Large central vacuole. Eg: Most of Angiospern.

· Water balance – water absorption – Transpiration.· Classification of plants based on water balance.

1. Hydrostable – Water balance remaining near zero. Eg: Trees, some grasses.

2. Hydrolabile – Larger losses of water and greater increases in cell sap concentration. Eg: Many herbs of sunny habilats.

· In the terminology of levitt.

Drought restance = Drought avoidance + Drought tolerance.

· All flowering plants can with stand severe deficits in the “dormant seed stage”.

· Water use efficiency (WUE) = Dry matter produced (DM) / Evapotamspiration (FT).

· Units of WUE gm/kg.

· WUE of C4 species is twice that of C3 species.

· Blossom – end rot of tomato fruits is the classic example of a drought related fruit disorder (due to ‘Ca’ deficiency).


· Air in motion is called “Wind”.

· Wind speed is measured by an “anemometer”.

· The term “leeward” refers to the direction toward which the wind blows.

· Composition of atmospheric air (% by volume).

N2 – 78.09; O2 – 20.93, Organ – 0.93, CO2 – 0.03, Misc – 0.02%

· For every gram of glucose formed 1.47 g of CO2 are required and the volume of air from which this amount can be withdrawn amounts is about 2500 litres.

· When CO2 content of the air is artificially raised to 0.1 and 0.3% by volume, C3 plants are able to bind 2-3 times and C4 plants 1-5 times.

· O2 concentration in the soil is lower than in the open air.

· BGA in rice fields produces 50 – 70 kg N ha-1 yr-1.

· The most important symbiotic N – fixation organisms are of the genus Rhizobium.

· Rhizobium fix 200 kg N per ha. per season.

· Actinomyces form root nodules in Casuarina.

· Study of soil formation, composition and classification of soil known as Pedology.

1. Oxylophytes – plants growing on acid soil. Eg: Pinaceae.

2. Halophytes – on Saline soils.

3. Psammophytes – on sandy soils.

4. Lithophytes – on rocks. Eg. Lichens, Selaginella.

5. Chasmophytes – On rock crevices. Eg: Equisetum.

· Mangrove plants exhibit vivipary, vast net work of roots, negatively geotropic Pneumatophores a specialized organs for respiration.

· Altitude refers to the position of the land surface to the mean sea level (MSL).

· “Epiphytes” are small herbaceous plants that grow on higher plant. In Epiphytes aerial roots are covered with greenish white tissue called “Valaman”.

· Total parasite “Orabanche cernua – on the roots of brinjal and Tobacco.

Striga asiatica – on toots of Sorghum and Sugarcane.

Cuscuta reflexa – On the stem of many herbs.

· Partial parasite : Loranthus longiflorus – On the stem of Neem, Guava etc.

· Mycorhiza is a group of fungi which live in (or) on the roots of higher plants.

· It is essential for development of pines and orchids.

· They absorbs N and P.

· “Resin” causes natural fire by constant rubbing.

· Fire stimulating the growth of certain plants like Cynodon to produce more seeds.

· Fire resistant and easily escape from fire injury – Pinus.

· Vanamahosov – Twice in a year – February and July.

· Light: less light intensity due to more mutual shading.

· Temperature less, humidity more, CO2 concentration less between it is utilized by plants in photosynthesis. O2 more.

· Temperature more, humidity less CO2 more, O2 less.


· Coal burning accounts for 50% of the SO2 pollution.

· The CO competitively inhibits N fixation by legumes.

· The content of smog are named as peroxyacyl nitrite (PAN) and Ozone.

· The symptoms of chlorine injury are of three basic types.

Chlorosis, Necrosis and redening.

· Bhopal gas tragedy – Methyl isocyanate (MIC).

· Lead taken up by plants is accumulated in the cell wall.

· Phytotron – F.W. Went.

· Climateron – Fritzwent.

· World most ultra – modern climatron is in “Japan”.

· Chrysanthemum – Short day plant.

· Tomato – Day neutral plant.

· In sorghum M 35- 1 varieties was developed in Mahatastra to scatter the needs of drought prone areas.


1. Natural ecosystem – Forests, Oceans, lakes.

2. Artificial Ecosystem – Cropped lands like rice, Sorghum.

· “Odum” classify ecosystem based on community metabolism ratio between photosynthesis and respiration.

1. P/R = 1 – Stabilized ecosystem.
2. P/R = > 1 – Autotrophic ecosystem.
3. P/R = < 1 – Heterotrophic ecosystem.

· For 500 cal/cm2/day total radiation, the net carbohydrate production would be 71 g/m2/day.

· The values of dry matter have been calculated per different latitudes of the globe by “Devent”.

· Production potential by Sinha and Swaminathan Pn = R X DI X 0.32 gm-2. Dry matter = 0.65 X Pn.

· Hydrology and physiography are most fundamental constraints of agriculture use of low lands.

1. Crop water use efficiency (or) consumptive use efficiency.
= Y/G + T + Es
Y = Yield
G = Amount of water required for growth.
T = Transpired through foliage.
Es = Evaporated from the soil surface

2. Field water use effeiciency = Q/G + T + Es + D.
D = Deep percolation
· WUE inverse relationship with R.H.

· WUE of C4 species is twice that of C3 species.

· The crop if it is having an LAI of 4-6 the light interception in the crop canopy will be good.

· Mulches economizing water use by the plant to the extenssion of 10-15%.

· Black mualches increase the temperature by 5-80C.

· Marimar calsssified the xerophytic plants into two distinct greeds of drought avuoiders.

1. Water Savers.
2. Water spenders.

· Water savers lose as little as 1/4300 of their dry weight per hour. Thus water spenders may be water as much as 5 lakhs times rapidly as water savers.

· Stomata can act as humidity sensors.

· Culticular to somatal ratio for mesophytes higher (1/2 to 1/5).

· While lsser in xerophytes (1/5 to 1/80).

· At the time of rains special type of roots develop in periheral region called as “Rain roots”.

· Metabolic water Eg: Cactus.

· Non succulent plants that fallow CAM mechanism. Eg: Prosophis juliflora

· Succulent type – Pine apple

· Plants capable of reaching water table are called “Phractophtes”.

· Dem absorption members of the family Chinopodiacea.

· The high rate of transiration of xeromorphe leaves caused by larger amounts as palisade tissue.

· Chreas is of mainly two types.

1. It may be deficit (or) water
2. Excess water.

· Same seeds avoid the effect of water stress by secretion of mucilage which effectively increase their contact with the soil. Eg: Mustard

· ABA increases under water deficit.

Growth parameters Symbol
1. CGR :C
2. RGR :R
3. NAR :E
4. LAR :F
5. LAI :L
6. LAD (leaf area duration) 😀

LWR = leaf weight ratio

SLA = Specific leaf area.

· Generally light has a positive effect on NAR and negative effect on LAR (-ve).

· “Hydrophonics” is the method of growing plants in nutrient solution.

· Term Allelopathy was coined by “Mulish”.

· Parthenium hysterophorus was controlled succeusfully by introducing Casia Uniflora.

· Biogeography is the study of present and paid geographical distribution of organisms on
 the earth.

· Energy transformation are one way.

· The movement of chemical elements in the ecosystem between the organisms and environment are known as “Biogeoc hemical cycles”.

· Cellular endosperm – Each neuclear division is accompanied by cell wall formation.

· Helobial endosperm – between nuclear and cellular.

· In coffee and pig weed endosperm is absent; perisperm (2n) act a storage structure. Endospermic seeds – legume – Fenugreek; dicots – castor.

Non endospermic monocots – Orchids.

Dicots – Peas, beans, grams.

· Living cells of outer most layer of endosperm – Aleuron layers.

· In a diitoped seed the surface of the coat shows a scar like structure at the place of it detachment from funicular and the structure is called – “Hilum”.

· The state at which seed reaches its maximum dry weight viability is, “Physiological maturity”.

· Physilogical maturity 30-40 DA anthesis in Sorghum.

· Viability means the capacity of a seed to germinate and produce a natural seedling.

· The potential with which the seeds produce healthy seedling – Vigour.

· Tetrazolium test (for Viability) is usually based on measuring the activity of “denydrogenase enzyme”, 2, 3, 5 triphenyl tetrazolium chloride red colour strain based on relative rates of respiration. It is also called “Quick test”.

· Mathematically speed of germination is expressed as “Coefficient of germination” (Vigour).

· “Exhaustive test” is used in cereals (Vigour test).

· “Lupin” seeds have largest period of viability – 10,000 yr.

· Haseringlon rules for storage: 1% moisture ↓ double life ↑ 5 – 60C ↓Double life ↑

· The arthematic sum of the storage temperature in degrees and percent relative humidity should not exceed 100.

· 8 – 10% moisture is favourable for better storage.

· Thoher CO2 can nitrogen gas increase the longivity of seed to onion and Wheat.

· Dimeasery in Epnul – Errbryes, Sunflower – seed coat.

· Failure of seeds to germinate for want of a particular environment factor is called “Quiscence”.

· Monoculture – Continous cropping of same crop species in the same piece of land.

· Poly culture – cultivation of different species.

· Individuals of Sps in which invitro – specific competition is dominant may show better growth in poly culture where as species more sensitive to inter – specific competition will show their best growth in monoculture.

· Physical (or) Chemical change prodcuced by stress is called strain.

· Cobalt is used for drought hardening in sunflower crop 1% CaCl2 – Groundnut.

· Accumulation of pesticide in an organism – Bioconcentration.

· A resource out of place – “Pollutant”.

· Allelopathic agent identified in Sorghum – Chlorogenic acid.

· Methane gas is mainly released from – Rice fields.

· World’s largest carbonate deposit were discouvered at “Mississipi”.

· Artificial rainfall – AgI.

· The transpiration/assimilation ratio is higher in C3 plants.

· Amino acid increases under water defiet – Proline.

· In case of grasses and fodder LAI – 6 – 11.

· Succinic acid for drought hardening in tomato.

· Plant that absorb dew very efficiently – Horse gram.

· Kaolinite – Reflective type of antitranspirant.

· Controlled burning to burn humus in acid soils

· Allelochemical “Parthenin” present in leaves of parthinum Sps.

· Example of plant that converts from C3 to C4 photosynthesis is Rice.

· In monocotyledon is referred as “Seutellum”.

· Embryo and embryonic axis are the life of a new plant.

· Shoot of the cotyledon – Coleoptile.

· Base of the hypocotyls – Coleothiza.

· Nuclear endosperm – free nuclei – Eg: Wheat.

· Primary dormancy – Innate dormancy.

· Secondary dormancy – Induced dormancy.

· Failure of germination of mustard seed exposed to high concentration of CO2.

· Immature embryo – Physiological dormancy. Eg: Apple, Pear.

· Breaking of dormancy with H2SO4 – Cotton.

· Senescence is ageing process.

· Heat stress – senescence interfere with Ca translocation.

· Antisenescence hormone – Cytokinins.

· Panicle senescence can be retarded by maintaining “Succinic dehydrogenase (SDH), ‘N’ application at booting stage.

· During senescence increase in activity of hydrolyzing enzymes.

· Downward movements takesplace in the sieve elements of phloem (Sugar).

· The process of sugar movement in the sieve tube – Translocation water and minerals – Xylem cells.

· The quantity of sugar translocated per unit cross sectional per unit time is called “Specific mass transfer”.

· Before reaching the sieve elements the sugars produced in green cells through layers of parenchyma cells. This process is called “phloem loading” or Vein loading. The translocated sugars leaving the elements is known as “phloem unloading”. Both loading and unloading takes place in “Parechyma cells”.

· Source – Sink (Sugar).

· Auxins cause apical dominance – cell elongation.

Initial flowering in long day plants – GA.

· Bolting (Production of floral axis) – GA promote bolting – stem elongation GA shows inhibitory effect on germination of rice seeds,

· Cell division – cytokinins.

· Richmand long effect – Cytokinins delay the senescence.

· When ethylene is applied on upper part of petiole it shows swelling and dropping of leaving.

· Application of ABA initiates flowering in short day plants. Inhibits in long day plants.

· Critical day length (photoperid require to induce flowers).

· Flowering induced chemicals – Florigen.

· Cytokinins are deviation of adenine molecule.

· Phytochrome is a blue proteinanceous pigment compased of “protein” and chromophore”.

Light red erosm

Pr Pfr → Photo convertion

Far red

730 nm → Thermal convertion

· Biological active form of phytochrome – Pfr.

· In shortday plants if Pfr/Pr ratio is high flowering inhibited, if ratio is low induced.

· In long day plants if PFr/Pr ratio is high flowering induced.

· Minimum vegetative growth (or) minimum number of leaves required for flowering is called “ripe – to – flower”.

· “Vernalisation” is defined as the method of inducing early flowering in plants by pretreatment at their seeds at very low temperature Eg: Winter wheat.

· Sugar accumulated in tomato stems during a low night temperature.

· The sleeping movement of leaves and flower – “Nyctinastic” due to absence of light (photonastic) – Endogenous rhythoms.

· Plants grown in darkness are called as “Etiolated plants”.

· Response of plant organs to light stimulus – Pholotropism.

Red light has less effect and blue light has more effect as phototropism.

· Photomorphogenesis control alter growth, development and differentiatine.

· Mobility of chloroplarle along with the plane of light polarization is phototaxy.

· Chlorophyll has “Cyclic tetrapyrolic ring structure”.

· 2 ATP are synthesized during cyclic photophosphorylation (PSI).

· In Non-cyclie photophosphorylation water is electron donar and NADPT is the electron acceptor. In non-cyclic photophospharylation one ATP one. NADPH + H+ are liberated.

· Photolysis of water takes place in (PSI & PSI) (700,680nm).

Caluin cycle:

C3 plants

1. Carboxylation phase: first table some product in C3 plants. PGA.

During dark phase CO2 is accepted by ROBP. ROBP → PGA.

2. Reduction: PGA → DPGA.


3. Regoneration phase: PGGK + DHAP Fructose 1, 0 diphosphate.

· One molecule of glucose is formed from 6CO2 by utilizing 18 ATP; 12 NAPPH + H+.

· 4 pathway (or) b carboxylation pathway. Eg: Maize, Sorghum.

· CO2 acccepter is pep – Phosphoenol pyruvate – in mesophyll cell.

· C4 plants show kranz anatomy – calvin cycle in “Bundle sheat cells” CO2, Pep , Oxalo acetic acid. This is stable product in C4 plants.

· C4 plants are more efficient carbon fixation than C3 plants.

· CAM – Pine apple, CO3 –by PEP using night and Calvin cycle using day.

· Inhabitory effect of O2 on an photosynethesis is called “War burg effect”.

· Photosynthesis is measured by IRGA (Infra-red gas analysis).

· Glycolysis – Cyloplasm.

· At the end of glycolysis two molecules of pyruvic acid two molecules of NADAP, 2 molecules of ATP are formed (Net).


2 PGA 2 PEP.

· Kreb’s cycle @ Citric acid cycle, Tri carboxylic acid.

· Connecting link between glycolysis and Kreb’s cycle – Acetyl co-A.

Succinic acid Fumaric acid.

4NADH2 → 3 X 4 12 ATP 8 ATP in glycolysis %
1 FADH2 → 2 ATP 30 ATP in Kreb’s cycle.
1 GTP → 1 ATP 38 ATP in respiration from 1 glucose.
15 ATP

· Electron transport – oxidative photophosphorylation – Cristae.

· In oxidative pentose phosphate pathway (OPP) Net ATP molecule – 35 ATP. (or) Hexois mano phosphate pathway.

· During the formation of root nodules curling of root hairs are caused by ‘IAA’.

· Pink pigment – leg hemoglobin.

· Bacterial dividing increases in size ant shape are termed as “Bacteids”.

· Leg haemoglobin protects “Nitrogenas enzyme”.

· Protein present in hoyumineur plant routs – “Lectins.

· Hetorocysts cells are responsitle for N2 fixation in BGA.

· Fe – Synthesis of legtacnoghbin; CO – essential for legmus to fix molecular nitrogen directly.

· MO – Alternate donor and acceptor of electron in N2 fixation.

· C – Electrons and 15 ATP are required for the production of two molecules of NH3.

· Reducing power for BGA – Water; for Sulphur bacteria – H2S.

· Conversion of NO3 into NH3 – Nitrate reduction.

· 8 e- are required for nitrate reduction.

· Nitrate reductase (MO) is called as “Inducible enzyme”.

· In Nitrate reductase – Fe/C4 are electron carries.

· NH3 + 2KGA → Glutamic acid; OAB → Aspartic acid.

· N2 fixation is measured by “Acetylene reduction method”.

· Mass of undifferentiated cells – Callus.

· “Umbellifevae” family has high tolipotency.

· Cells have vacole. Vacoles retain H2O due to “Osmosis”.

· H2O is a major constitient of Protoplasm

· Water potential is measured in “Megapascel”.

· Liquid H2O potential is “Zero”; – 1.5Mpa → growth stop; – 3Mpa → Willing.

· Ψw = Ψm + Ψs + Ψp; Ψw = water protential, Ψm= matic potential, Ψs= Solute potential,
Ψp= pressure potential.

· Matric potential is high in unvaculated cells (or) in old cells.

· Hydrostntie pressure, damaged in voate the to inwardly dirceled wall pressure – “Turger

· The quality and appearance of vegetables is mainly duacta “turgor pressure.

· Moil abundant Xanthephyll – 1.4 lin.

· “Beer & Lambard’s Law” – Spectrophotometer principle.

· In a ray of manuchromalic light paises through absorbing medium its intensity decreases with increasing the length of the medium and concentration (Ceer’s).

· Chloaphy disisnvent in “Acetone”.

· Caluin cycle “Thermosensitive”.

· Cluster grown of concentration O2 acid → Casuncle.

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