Drought Stress in Plants: Physiological and Biochemical Effects for Exams

[00:00:00]hello good evening and welcome to all of you this is rajes and I am here to discuss the new lecture on the effect of broad stress on plant growth and development so friend this is a one of the very important topic for all the competitive exams and in this lecture we will discuss the different effects of the Bro stress on plant physiological morphological biochemical processes so friends in in the last class the atic basics of atic stress we had discussed that there are so many types of stress and drought is a one of the major stress which affect the different processes like physiological morphological biochemical and molecular in the plants and also ultimately reduce the yield potential of all the crops so in this lecture we will discuss the some effects of the Dr stress so Dr is defined as the event okay when there is a prolong shortage in the supply of water means the water supply is less for a long period then there will be a shortage of water it could be atmospheric means there will be a less rainfall below the average rainfall or it could be agriculture drought when the irrigation supply is less than the demand of irrigation then soil DRS means there will be a shortage of surface and groundwater and last one is the physiological drought when the transmation is higher than the water uptake so these are the conditions which makes the root stress or water stress means if there is a less rainfall or there will be a less irrigation or there is a less ability of surface and groundw and the transmission is higher than the water upate so this condition increase the water stress also the occurrence of bradress at different growth stage of the plants interfere with the normal plant functioning which results in the reduction in final so friends you know that there are so many types of growth stages growth stages in the plant so first is the germination germination phase second that seedling establishment is there seing establishment or you can say it is juvenile phase then there is a vegetative phase then reproductive phage and then maturity so are number of growth phases in the plant growth cycle okay so they are the effect of drought is different at the different growth stages means drought could be more sensitive for the germination and reproductive stage as compared to the vegetative stage so there will be a different effect of the RO at the different stage and interfere with the normal plant functioning which ultimately cause the reduction in final yeld so the effect of dro St vary with the crop stage of even uh the effect of drought also vary with the different types of crop means the effect of drought means in the wheat crop the effect of drought is different than the rice crop and also some crop like sorghum they are more tolerant as compared to the other crop so they are there will be some dra tolerant crop or some Ro susceptible crop so the effect also vary with the crop and the different growth stages also it is BU with the local environmental conditions okay like if we will see that in the Rajasthan Athan there is a drought then there is also high heat because there is a very high temperature so generally crop faes the dro and heat stress so the drought affect the seed germination vegetative reproductive growth as well as maturity stage of a crop at different scales means it vary with the different crop and different St also it is vary with the frequency and duration of the drao stress means the dra stress is the high moderate or low so it is also very with the means there will be a low could be low Dr stress moderate or high Dr stress it is also vary with the duration means Ro stress is for short duration moderate duration or long prolong period so when the Dr stress is for prolong period and the frequency is also High then there will be a high there will be a high effect means they will more affect the grow growth and development so the Dr mainly reduce the mechanism of plant that interfere that reduce the crop yield like they decrease the Kopi absorption of P me they reduce the photosynthetic active radiation they reduce the radiation huge efficiency also they reducing the harvesting index hi so they are also affecting the several mechan so this is about the some basic of the Dr stress now come to the effect of broad stress on the plant so first is the this impaired the germination and poor stand establishment so this is the first effect of the first growth stage that at germination and seedling establishment stage this draw stress reduce the germination percentage or germination potential hypoc length suit and root pH WD also the seedling length seedling length and the phas and dry weight of the seedling decrease the cell elongation because there will be less water available for the growth and also they reduce the expansion of cells and reduce the mitosis or cell division so these are the um important or man effect of the dro stress at the initial germination phase so in this fix also you can see that in control condition there will be a good growth but at hyroad condition there will be a reduction in seedling length seedling growth also germination potential ultimately they reduce the seedling figer so these are the effect of Ro stress on the initial phage next it reduce the yield determining or yield structure attributes okay so draw reduce the time to enthesis so some plant use the enthesis time to take unto enthesis they also do the short and the grain filling periods so these are mainly R escapers mechan means they are reducing the the period for the growth and development in the valley they reduce the number of ters per gra tillers also reduce the grain per plant and also reduce the individual grain weight means tast weight in which water stress redu the yield by the delaying the silking intervals in so soin Ro stress reduce the total s seed yield and the branch seed yield means from the primary and secondary Branch they affect the CD at high concentration of drought at flooring could be result in the beess of the p means there will be a no seed formation because of the reduction in the assimilate flux to the developing ear blue reduce when the drought condition is very high or water stress for the prolong period Then it can cause the baroness in the ports because it reduce the assimilate paring to the grain part or developing grains it also decline in Grain yield from reduce sucrose synthetic activity means they reduce the syntheis of the sucros synthetic enzy so ultimately it reduce the r gild so these are the effect on the yield attributing traits then water relation so you know that there is a water stress so it will ultimately affect the water relation sources of the plant so it reduce the relative water content leaf water potential stoal conductance transformation rate that LE temperature kop temperature also influenced by the plant water relationship means they increase the leaf and Kopi temperature and reduce the relative water content leaf water potential instal conductance and transmission R so ultimately they affect the plant water relationships in a study it was found that in Opia there will be a total 50 27% of total water content is reduced under the r stress what it increases the water uency so we can say that if there will be a Dro stress or water stress then water uh plant use water more efficiently because it need to save for the surv so they increase the water VI efficiency and then next is the neutr nutrient relationships so you know that water is important for the nutrient uptake and transport okay so it will reduce the there will be a lower absorption and transport of the nutrient from the soils it is also there will reduction in the energy ability ability for the assimilation of nitrate and ammonium also decrease the nitrogen use efficiency and nutrient acquisation so the all the aspects of the nutrient relationships like uh uptake transport absorption uh acquisition assimilation the all the process are reduced under the thr stress then assimilate fening so you know that uh the Water stress reduce the assimilate paring and reduce the uh transfer of the assimilate to the grains so it also reduce the alteration of dry matter to the roots and there will be a decrease in the photosynthesis means there will be a decrease in the source disrupt metabolic level of so crow in the leaves that SP over a decrease export rate means there will be a less synthesis of suos so ultimately it decrease the exports of the uh export of the carbohydrates decrease the sucrose export to the sinks so there will be a less avability of srose to the sink tissue like Roots grains Okay so it causes the reproductive abortion okay also it reduce the invert activity so this it cause the improper unloading of the FL also inhibit the cell division in the developing embo and endosperm which result in the weak sink intensity ultimately cause the fruit abortion so these are the sum effect of the dra stress now come to the photosynthesis so dra stress reduce the Leaf exp expansion which reduce the photosynthetic mry means it damage the photo system first second also some proteins D1 D2 also it's redu the Risco activity okay and there will be a premature Leaf sense so it can also be seen in many field condition that underwater condition plant start sense very early also it decrease the food production and limited CO2 uptakes then photosynthesis can be reduced by the there will be three reasons that it affects the stomat oscillation means reduce the CO2 up then closing of stomata reduce the TG pressure also reduce the CO2 inflow and there will be a production of R so environmental condition that enance the rate of transp also increase the pH of the leaf cell which can promote the AV accumulation and decrease the stomatal conductance so there will be a under drao condition there will be a movement of stomata and formation of AA then photosynthetic enes so it decrease the rubisco activity also cells inas increase cell inrage increase solute concentration rapid diminution of rubiscos small subunit means damaging of a small subunity carox reduction of carox efficiency speed of rubisco also reduced and also some enzymes like pep cage nadp mic enzymes rubisco lactose B phosphate ppdk pyrro phospher diin these some important enzymes also affected under the Thro stress and next third one is the ATP synthesis that draw stress limit the ATP ATP synthetic by affecting the ATP activity okay so photosynthetic can be reduced by the estral movements photosynthetic enzymes or ATP syntheis respiration so at initially it increase the respiration means degradation of metabolites but at severe stress it reduce the respiration because of the reduce suit or root biomass also reduction in the photos synthetic activity increase in the r activity and electron goes to the alternate pathway so they will be initially there will be increase in the respiration activity But ultimately it reduce the respiration because due to reduction in the biomass photosynthesis and there will be more R activity and electron goes to the alternative Pathways and last one is the oxidative damage means there is a production of that peroxide hydroxide ions which damage the ultimately the cells so this figure describe the all the effects of the dra stress on the different processes and functions like seed germination already discussed is reduce the seed germination coefficient velocity of germination seedling energy also reduction in the root lens root length and sidling wigers at that same time it reduce the amage protage and liage activity which decrease the seed storage okay also affect the embro growth okay also it increase the ABA and GA ratio okay so decrease the germination because AA promote the dorcy and GA promote the germin then there will be accumulation of stress proteins such as heat so protein Lea protein late emogen late ambro genic aboundant proteins and dehydrations so they will be used for the r tolerance also there will be expression of some stress responsive transcription factors so these are occurs during the germination times in case of mineral nutrition it affect the uptake and transport of essential nutrients also it affect the nutrient Transporters like there will be hkt and there are so so many Transporters which are affect under the do stress then photosynthesis it reduce the total chlorophyll content pigment composition and increase the maintenance respiration or reduce the growth respiration means the respiration responsible for the growth is reduced but maintenance because there will be more damage so need to be maintained so increase the maintain maintenance respiration also affect the enzymes of crab cycle C3 C4 and phosphation and electron transport so all the most of the enzymes are affected under the r stress also affect the component of the photosystems like D1 protein D2 proteins rubisco fireo hosage also affected under the water stress so also it the Dr stress affect the water uptake and transport by the affect the gene associated with the aquaporin you know that aquaporin and osmotic adjustment okay red the uptake of water due to reduce water potential because water is already available is means ability is very less so it reduce the uptake of water it also reduce the plant growth and development bya affecting the leaf area plant height FR and dry biomass and assimilating paring during the vegetative P okay plant growth Regulators so if it affect the fysic acid GE ratio accumulation of cyto ethylene brain jasmonic acid and oxin so these hormones are also affected under the r stress and the antioxidants so you know that there is a production of reactive oxygen species like hydroxy H2O2 and there are so many even super oxide so they are reactive oxygen species which damage the cell organy by the lipid peroxidation so opposite to this plant develop the antioxidant defense system so most of the enzymes like superoxide dis mutage catalis peroxidase melide also gluten reduct as forward prod so so many enzymes are also affected under the broad strance and beaken the uh defense system of the plant and if we will see the RS rate means root structure architectures so it affect the root length root width volume density hydraulic conductivity root pulling Force root length density deeper root width and so many root trats also affected by the Dr stress stomal movements so it reduce the stomal conductance CO2 fixation and transpiration and yield and yield attributing so it reduce the qualitative traits like protein content vitamins ion fatty acid and lipid content in the grain so it reduce the quality of the grains and it also affect the pollination fertilization panicle length panicle weight seed number and gra re so these are the yield structure or yield attributing traits okay so yield attributing traits also affected under the r stress and there will be some molecular changes like it also affect the transcript expression of the gene associated with the antioxidant enzymes like sod cataly peroxidise MDA PPO grn apx and also genes associated with the photosynthetic enzyme and metabolic genes so these also affected it can can be increase or decrease under the uh this Dr stress also it affect the plant growth and development by the modulate expression of transcription factors transcription factors like maybe is there neck is there Medbox is there work is there mice is there D is there so these transcription factors are also affected under the dra stress so friends in this lecture we have discussed that the dra stress is a qu tra means it affect the many trait at A T from seed germination to the maturity different enzymes activity different growth and development traits so ultimately these traits affect the yield and the yield potential of the crop so hope you understand the topic and thank you very much