PLANTS AND ENVIRONMENTAL FACTORS

its about .. An understanding of the ways individual plants and their physiology are impacted by different factors of the environment is an essential component in the design and management of cropping system The ecological study of individual plant response to the diverse factors of environment (autecology or physiological ecology) is a foundation of agroecological understanding

THE PLANT Photosynthesis Carbon Partitioning Nutritional Needs Transpiration

1. Photosynthesis “Plants convert solar energy into chemical energy stored in the chemical bonds of sugar molecules” this process is IMPORTANT for plant growth and survival

Remember what plants need… Photosynthesis light reactions light H2O Calvin cycle CO2  sun  ground  air

Fotosintesis Proses dimana organisme yang memiliki kloroplas mengubah energi cahaya matahari menjadi energi kimia Melibatkan 2 lintasan metabolik Reaksi terang: mengubah energi matahari menjadi energi seluler Siklus Calvin: reduksi CO2 menjadi CH2O

Simple equation : 6CO2 + 12H20 + light energy C6H12O6 + 6O2 + 6H2O

powers most cellular work Light energy ECOSYSTEM CO2 + H2O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O2 ATP powers most cellular work Heat energy Energi mengalir ke dalam suatu ekosistem sebagai cahaya matahari dan meninggalkannya dalam bentuk panas

Types of Photosynthesis C3 photosynthesis The most widespread type of photosynthesis. Beans, squash, and tomatoes C4 photosynthesis Corn, sorghum, and sugarcane CAM (crassulacean acid metabolism) photosynthesis Cacti, agaves, bromeliads, and others

C3 plants The first stable compound formed in dark reactions (Calvin cycle) is 3-carbon compound (glucose) A problem with C3, photosynthesis is always accompanied by photorespiration which consumes and releases CO2 in the presence of light it wastes carbon fixed by photosynthesis - up to 50% of carbon fixed in photosynthesis may be used in photorespiration

C4 plants A better way to capture CO2 In this system, CO2 is incorporated into 4-carbon compounds before it enters the dark reactions. Then enzymes break loose the extra carbon as CO2. the CO2 is then used to form the 3-carbon compounds used in dark reactions. adaptation to hot, dry climates Enables photosysthesis accur while stomata are closed

sugar cane corn

Photorespiration is nearly absent in C4 plants - so greatly increases their efficiency - this is because a high CO2: low O2 concentration limits photorespiration Thus net photosynthetic rates are higher for C4 plants (corn, sorghum, sugarcane) than in C3 relatives (wheat, rice, rye, oats)

CAM (Crassulacean Acid Metabolism) plants separate carbon fixation from Calvin cycle by Keep close stomates during day open stomates during night at night, open stomates & fix carbon in “storage” compounds (4-carbon coumpond malate and stored in vacuoles in day, close stomates & release CO2 from “storage” compounds to Calvin cycle CAM plant common in hot and dry environment, they include many succulents, pineapple, cactuses, agaves, bromeliads

CAM plants

2. Carbon Partitioning how plant distributes the carbon compounds derived from photosynthesis and allocates them to different physiological processes and plant parts

Carbon Partitioning The carbon compounds produced by photosynthesis play critical role in plant growth and respiration Humans select plants that shunt more photosynthate to the harvestable part of crop.

Nutritional Needs Carbon, hydrogen and oxygen make up approximately 95 % of the average plant’s fresh weight The elements that make up the other 5 % of living plant matter must come from soil (essensial nutrients)

Nutritional Needs Macronutrient : N, P, K and Ca, Mg, S Micronutrient : Fe, Cu, Zn, Mn, Mo, B, and Cl

Nitrogen : major component of proteins required in enzyme synthesis needed in large amounts by plant major component of proteins required in enzyme synthesis required in chlorophyll synthesis adsorbed by plant as NO3- or NH4-

Phosphorus : Important component of nucleic acids, nucleoproteins, phospholipids, ATP Cell membranes depend on phospholipids Absorbded as phosphates form through plant roots

Potassium: Its involved in osmoregulation (stomatal movement) As cofactor for many enzyme systems Needed for cell devission and growth Linked to cell permeability Plant show better resistance to disease and environmental stress when potassium supplies are adequate

Nutrient Processes Boron (B) Carbohydrate transport and metabolism, phenol metabolism, activation of growth regulators Chlorine (Cl) Cell hydration, activation of enzymes in photosynthesis Copper (Cu) Basal metabolism, nitrogen metabolism, secondary metabolism Iron (Fe) Chlorophyll synthesis , enzymes for electron transport Manganese (Mn) Basal metabolism, stabilization of chloroplast structure, nitrogen metabolism Molybdenum (Mo) Nitrogen fixation, phosphorus metabolism, iron absorption and translocation Zinc (Zn) Chlorophyll formation, enzyme activation, basal metabolism, protein breakdown, hormone biosynthesis

3. Transpiration the continual flow of water from the soil, into the roots, up the stem to the leaves, and out of the leaves through the stomata Water moving between soil and plants flows down a water potential gradient

Water movement between plants and soils

T r a n s p i r a t i o n

Interaction Plant -Environment A Plant’s Place in the Environment - Each species occupies a particular place in the ecosystem, known as the habitat - within its habitat, the species carries out a particular ecological role or function, known as the ecological niche of that species

Interaction Plant -Environment Responses to Factors of the Environment Setiap fase perkembangan tanaman melibatkan respon perubahan secara fisiologis. Sebagian besar respon tanaman berkaitan langsung dengan kondisi lingkungan - Triggered Responses - Dependent Responses - Independent Responses

Triggered Responses respon tanaman yang dipacu oleh adanya eksternal stimulus tertentu Dependent Responses respon tanaman yang tergantung pada keberadaan secara terus menerus kondisi lingkungan eksternal tertentu Independent Responses respon tanaman yang ditentukan oleh kondisi fisiologis tanaman; mis: tanaman jagung akan berbunga karena fase tertentu dari pertumbuhan dan perkembangan sudah tercapai.

Interaction Plant -Environment Limits and Tolerances Each environmental factor has both minimum and maximum levels, tolerance limits, beyond which a particular species cannot survive

Tugas Buat tulisan tentang - fotosintesis - partisi karbon (asimilat) - transpirasi