LECTURE 3: INTRODUCTION TO LIGHT RESPONSE

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http://smtom.lecture.ub.ac.id/ Password: https://syukur16tom.wordpress.com/ Password: LECTURE 3: INTRODUCTION TO LIGHT RESPONSE LECTURE FLOW 1.

1 Password: Password: LECTURE 3: INTRODUCTION TO LIGHT RESPONSE LECTURE FLOW 1. INTRODUCTION 1. Definition 2. Other Tropism 2. TYPES OF LIGHT EFFECTS 1. Several Types of Light Effects 2. Potato Case 3. PHOTOMORPHOGENESIS 4. CASES OF PLANT RESPONSES 1

2 LECTURE OUTCOME After the completion of this lecture and mastering the lecture materials, students should be able to 1. explain the meaning of photomorphogenesis, phototropism, photoperiodism, and geotropism 2. explain various types of light effects on plant growth and development explain the mechanism adaptation of mangrove to salinity explain some changes in plants due to breeding program INTRODUCTION 1. Definition Plants show many different responses or reactions to light and most of which can be classified into four types; photosynthesis, photomorphogenesis, phototropism and photoperiodism - Photomorphogenesis is the regulatory effect of light on the growth, development and differentiation of plant cells, tissues and organs. - Phototropism is the growth response of a plant in response to light direction. Different parts of a plant exhibit different reactions to light. Stems exhibit positive phototropism while most roots exhibit negative phototropism. 2

Phototropism is one way a plant can maximize its exposure to sunlight. This is also an important survival tactic because plants need sunlight to make food. https://encryptedtbn3.

Other Tropisms A tropism (from Greek τρόπος, tropos, "a turning") is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in

3 Phototropism is one way a plant can maximize its exposure to sunlight. This is also an important survival tactic because plants need sunlight to make food. rzhzxiebley5ff-lfkvrxavffdqsek20cynvb1r24 nses.htm 2. Other Tropisms A tropism (from Greek τρόπος, tropos, "a turning") is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. Geotropism is the growth response of a plant in response to gravity. Roots exhibit positive geotropism while stems and leaves exhibit negative geotropism. 3

4 Hydrotropism is the growth response of a plant to water. Roots exhibit positive hydrotropism. Thigmotropism is the growth response of a plant to physical contact (touch). Plants that cling to physical structures such as walls exhibit positive thigmotropism. 4

Inhibition of the elongation of the hypocotyls Inhibition of translocation from the cotyledons Increase of the surface area of the cotyledons Unfolding of the cotyledons lamina

5 Unfolding manner of common beech leaves: (a) a bud, (b) buds just after opening, (c) an early stage of unfolding, and (d) corrugated leaves. a b c d Nastic movement, Thigmotropism or Circadian response 2. TYPES OF LIGHT EFFECT 1. Several Types of Light Effects Inhibition of the elongation of the hypocotyls Inhibition of translocation from the cotyledons Increase of the surface area of the cotyledons Unfolding of the cotyledons lamina Development of hairs at the hypocotyls Opening of the hypocotyls hook Development of the primary leaves Development of mature leaf primordia Increase in the negative geotropic reaction of the hypocotyls Development of xylem elements synthesis 5

6 Differentiation of the stomata within the epidermis of the cotyledons. Development of super-etioplasts in the cotyledons mesophyll. Changes in the intensity of the cell respiration. Synthesis of anthocyanin in the cotyledons and the hypocotyls. Increase in the synthesis of carotenoids. Increase in the capacity of the chlorophyll synthesis. Increase in the RNA synthesis within cotyledons. Increase in the protein synthesis within cotyledons. Intensification of the storage fat breakdown. Intensification of the Storage protein breakdown. Increase in the synthesis of ethylene. Acceleration of the Shibata-shift within the cotyledons Determination of the cotyledons capacity to photophosphorylate Modulation of the cotyledons enzyme synthesis Inhibition of arabidopsis hypocotyl elongation by jasmonates is enhanced under red light in phytochrome B-dependent manner. MeJA action still remained in the coi1 mutant, and (+)-7-iso-JA-L-Ile, a well-known active form of jasmonate, had a weaker effect than MeJA under the red light condition. Methyl jasmonate (MeJA), 6

Inhibition of arabidopsis hypocotyl elongation by jasmonates is enhanced under red light in phytochrome B dependent manner Bc Rc a Hypocotyl lengths of 6-day-old Col seedlings with 0, 1, 10, 30, 50,

7 Inhibition of arabidopsis hypocotyl elongation by jasmonates is enhanced under red light in phytochrome B dependent manner Bc Rc a Hypocotyl lengths of 6-day-old Col seedlings with 0, 1, 10, 30, 50, or 100 μm MeJA on MS medium (with 1 % sucrose) under μmol m 2 s 1 Rc, 2 5 μmol m 2 s 1 Bc or μmol m 2 s 1 FRc. b Photograph of 6day-old Col and coi1-16s seedlings grown on MS medium (with 1 % sucrose) with different concentrations of MeJA under μmol m 2 s 1 Rc. c Hypocotyl lengths of 6-day-old Col and coi1-16s mutant seedlings with 0, 1, 10, 30, 50, or 100 μm MeJA treatment on MS medium (with 1 % sucrose) under μmol m 2 s 1 Rc. For a and c data are the mean ± SD (n = 20 seedlings per genotype). Chen et al. (2013) Methyl jasmonate (MeJA), red light (Rc), blue light (Bc), far red light (FRc) 2. Potato Case A potato left growing in darkness produces shoots that look unhealthy and lacks elongated roots. These are morphological adaptations for growing in darkness, collectively called etiolation. After exposure to light, a potato undergoes changes called de-etiolation, in which shoots and roots grow normally. A potato s response to light is an example of cell-signal processing. The stages are reception, transduction, and response. 7

week sexposure exposureto to (b) natural

most obvious in germinating seedlings, but

ways throughout all stages of development.

8 (a) Before exposure to light (a) Before exposure to light (b)after Afteraaweek s week sexposure exposureto to (b) natural daylight natural daylight 3. PHOTOMORPHOGENESIS 1. Typically, photomorphogenic responses are most obvious in germinating seedlings, but light affects plant development in many ways throughout all stages of development. Photomorphogenesis is the process by which plant development is controlled by light Next 8

Amylase accelerates hydrolysis of starch Phytochromes, pigments containing protein functioning as

9 Process: Seed Germination 2. Gibberelic Acid - Arrives at aleurone cells Activates certain genes 3. Transcription Transportation Translation amylase 4. Amylase accelerates hydrolysis of starch Phytochromes, pigments containing protein functioning as photoreceptor, is involved in some response of plants to light Phytochromes are located in cytoplasm for the unactivated form, and in the nucleus for the activated form 9

10 Phytochromes are red (R)/far-red (FR) light photoreceptors that play fundamental roles in photoperception of the light environment and the subsequent adaptation of plant growth and development. There are five distinct phytochromes in Arabidopsis thaliana, designated phytochrome A (phya) to phye. phya is light-labile and is the primary photoreceptor responsible for mediating photomorphogenic responses in FR light, whereas phyb-phye are light stable, and phyb is the predominant phytochrome regulating de-etiolation responses in R light. Phytochromes are synthesized in the cytosol in their inactive Pr form. Upon light irradiation, phytochromes are converted to the biologically active Pfr form, and translocate into the nucleus. phyb can enter the nucleus by itself in response to R light, whereas phya nuclear import depends on two small plant-specific proteins FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) and FHY1LIKE (FHL). Phytochromes may function as light-regulated serine/threonine kinases, and can phosphorylate several substrates, including themselves in vitro. Phytochromes are phosphoproteins, and can be dephosphorylated by a few protein phosphatases. 10

11 Absorption spectra of the two forms (Pr and Pfr) of phytochromes. The Pr form absorbs maximally at 660 nm, while the Pfr form absorbs maximallyat 730 nm. The biosynthesis pathway of Arabidopsis phytochrome chromophore. Image adapted from Kohchi et al. (2001). 11

12 (B) Red (R) light triggers a Z to E isomerization in the C15 C16 double bond between the C and D rings of the linear tetrapyrrole (upper panel), which is accompanied by rearrangement of the apoprotein backbone (lower panel; adapted from Bae and Choi, 2008). 12

Pr form is first synthesized and, after exposed to red, converted to

13 What is the type of phytochromes actually inhibitory for seed germination? What is the first event in germination? Pr form is first synthesized and, after exposed to red, converted to Pfr form which then enters nucleus and binds to DNA protein to inhibit or activate specific genes 13

The case of Mougeotia An example of Photomorphogenesis is the rotation of chloroplast observed in Mougeotia - Mougeotia is a filamentous green alga whose cells contain a single ribbon-like

14 The case of Mougeotia An example of Photomorphogenesis is the rotation of chloroplast observed in Mougeotia - Mougeotia is a filamentous green alga whose cells contain a single ribbon-like chloroplast nestled between two large vacuoles and surrounded by a layer of cytoplasm. Phytochrome is implicated in the rotation response of Mougeotia chloroplast because the system is most sensitive to red light, and the red light effect can be reversed by far-red light. - Using microbeams of red and far-red light, Wolfgang Haupt and his coworkers in Germany showed that in Mougeotia, phytochrome is localized near the periphery of the cytoplasm in the vicinity of the plasma membrane. 14

- When a microbeam of red light was directed at the cell surface under a microscope, the edge of the chloroplast adjacent to the microbeam rotated 90, even though the chloroplast itself was not

- The chloroplast can rotate about its long axis and can respond to light by orienting perpendicularly to the direction of light The perpendicular orientation is referred to as "face position.

15 - When a microbeam of red light was directed at the cell surface under a microscope, the edge of the chloroplast adjacent to the microbeam rotated 90, even though the chloroplast itself was not illuminated. - The chloroplast can rotate about its long axis and can respond to light by orienting perpendicularly to the direction of light The perpendicular orientation is referred to as "face position." Haupt and his coworkers discovered that the ability of plane-polarized red light to cause chloroplast rotation depends on the plane of polarization relative to the long axis of the cell. This phenomenon is depicted in the experiment when half of a cell was illuminated over the entire surface with polarized red light (R) vibrating perpendicular to the cell axis; the other half was illuminated with light vibrating parallel to the cell axis. The chloroplast rotated from the profile to the face position only in response to red light vibrating in the perpendicular direction, producing a twist in the chloroplast. On the basis of these experiments, it was concluded that phytochrome molecules have a defined orientation (Haupt 1982). 15

16 31 4. CASES OF PLANT RESPONSES 1. Response to drought stress 16

2. Mangrove Adaptation to Salinity Like all other halophilous plants (plants that grow on saline soil or soil that affected by salt water), mangroves can tolerate higher internal salinity.

balance Salt Excretion. Some mangrove plants are salt secretors. The common salt concentration in the sap is high at about one-tenth that of sea water.

17 2. Mangrove Adaptation to Salinity Like all other halophilous plants (plants that grow on saline soil or soil that affected by salt water), mangroves can tolerate higher internal salinity. Mangroves balance the osmosis through accumulating carbohydrates of small molecular weights inside their bodies instead of proline, an amino acid that most halophilous plants accumulate for the balance Salt Excretion. Some mangrove plants are salt secretors. The common salt concentration in the sap is high at about one-tenth that of sea water. Salt is partially excluded by the roots and the salt is excreted by the salt glands by the plant expending energy The concentrated salt solution evaporates near the gland, becomes crystals which are removed by wind or rain. One can taste the salt by licking the leaves of these species to confirm this! Salt crystals on the leaves of Acanthus ilicifolius Examples: Api-api (Avicennia species), Jeruju (Acanthus species) or Kacang-kacang (Aegiceras corniculata) 17

Salt gland from the mangrove swamp species Aegiceras corniculatum. (a) Secretory cells surrounded by cuticle and epidermal cells [after W. P. Anderson (ed.

Other mangrove plants can prevent salt from entering xylem of the roots and stop salt being transported to tissues through ultrafiltration.

18 Salt gland from the mangrove swamp species Aegiceras corniculatum. (a) Secretory cells surrounded by cuticle and epidermal cells [after W. P. Anderson (ed.), Ion Transport in Plants, Academic Press, New York, 1973]. (b) Section through the gland. Salt Exclusion. Other mangrove plants can prevent salt from entering xylem of the roots and stop salt being transported to tissues through ultrafiltration. However, even with this, exclusion is not complete. Some salt is lost by transpiration through the leaf surface or accumulates in some cells of the leaf. Species deposit a good part of the excess salts in the old leaves which are shed Examples: Bruguiera, Lumnitzera, Rhizophora or Sonneratia 18

19 Shedding of plant parts. They store salt inside the vacuoles or fix it in the leaves in the form of crystals. Salt are expelled by the mother plant when the leaves fall. Some species of mangroves can regulate salinity inside their bodies by a mix of the aforementioned methods. Examples: Many-petaled Mangrove, Milky Mangrove Xeromorphic Characters. Mangroves are xeromorphic plants, therefore they must preserve a high density of water to minimise absorption of sea water, which has a high salinity. To adapt this unique habitat, mangroves develop some special features: - - Succulence some species of mangroves contain water storing tissues in the leaves Thick cuticle ceraceous cuticle and periderm Sunken stomata concave breathing pores at the back of the leaves Buttress root thick roots to absorb water on the soil surface Tiny hair Some leaves possess hair-like trichomes to reduce water loss Active growth and increase in succulence of cells. Mangroves can grow rapidly and have high cell succulence. These increase their salt storing capacity and weaken the effect of high salinity. Reduction of transpiration rate. Reduce transpiration on leaf surface can minimise salt intake. 19

20 3. Breeding Program In the last few decades, the breeding of agricultural crops for higher yields has been very successful. Breeders usually select for high-yielding genotypes empirically, without particular attention to specific plant traits that might be conducive to higher yields. However, comparing old, low-yielding lines of any crop with advanced, high-yielding lines shows clearly that many morphological, physiological, and biochemical traits have been altered by the intense selection pressures for higher yields Stomatal conductance. Stomatal conductance has increased in parallel with agronomic yields in irrigated Pima cotton (Gossypium barbadense) selected for higher yields at a high temperature. The figure shows the relationship between lint yield and stomatal conductance in a historical series of Pima cotton grown in Arizona. The abbreviations P32 and PS-1 through PS-7 designate successive commercial releases between 1949 and (From Lu et al ) 20

21 Frequency distribution of stomatal conductance in parental populations of the high-yielding Pima cotton line (P73), the old Pima line (P32), and their F 1 and F2 progeny. (A) Nonoverlapping distribution of stomatal conductance in the two parental populations. (B) Distribution of stomatal conductance in an F1 population from a cross between the two parents. (C) Distribution of stomatal conductance in an F2 population derived from F1 parents. (After Percy et al ) The relationship between grain yield and stomatal conductance in a historical series of semidwarf bread wheat grown in Ciudad Obregón, Mexico. The abbreviations H1 through H8 designate successive commercial lines released by the International Maize and Wheat Improvement Center between 1962 and (From Lu et al ) 21

The importance of membrane lipids for tolerance to low temperatures How changes in relative levels of cis-unsaturated molecular species of phosphatidylglycerol (PG) in thylakoid membranes of (A)

22 The importance of membrane lipids for tolerance to low temperatures How changes in relative levels of cis-unsaturated molecular species of phosphatidylglycerol (PG) in thylakoid membranes of (A) tobacco and (B) Arabidopsis affect sensitivity to chilling. (After Nishida and Murata 1996.) Ice Formation in Higher-Plant Cells Temperature of parenchyma cells in cucumber (Cucumis sativus) fruit during freezing. The temperature was recorded with an electronic device, a thermistor, inserted into a 5 20 mm cylinder of tissue and immersed in a coolant at 5.8 C. (A B) Supercooling. (B C) Release of heat during freezing in cell walls and intercellular spaces. (C D) Supercooling. (D E) Small heat spikes released during intracellular freezing of individual protoplasts. (After Brown et al ) 22

http://leavingbio.net/thest ructureandfunctionsofflo wers%5b1%5d.htm 45 Photomorphogenesis as a morphological and as a cellular process.

23 ructureandfunctionsofflo wers%5b1%5d.htm 45 Photomorphogenesis as a morphological and as a cellular process. The left photos show the change in form of an Arabidopsis thaliana seedling grown in darkness (top) or in white light. The right hand illustration shows the change in chloroplast structure and diagrams the progress of light signals through two receptor systems, cryptochrome and phytochrome. Adapted from Biochemistry and Molecular Biology of Plants, (c) American Society of Plant Biologists, with permission. Source: Shinkle (?). 23

CONTROL OF PLANT GROWTH AND DEVELOPMENT BI-2232 RIZKITA R E

CONTROL OF PLANT GROWTH AND DEVELOPMENT BI-2232 RIZKITA R E The development of a plant the series of progressive changes that take place throughout its life is regulated in complex ways. Factors take part