The Temperature Factor - Crop Ecology and Morphology - Lecture Slides | CSS 200, Study notes of Agricultural engineering

Download The Temperature Factor - Crop Ecology and Morphology - Lecture Slides | CSS 200 and more Study notes Agricultural engineering in PDF only on Docsity! Crop and Soil Science CSS 200 Crop Ecology and Morphology The Temperature Factor • Temperature stress can cause injury or death of the plant. • Temperatures outside the optimum for various plant processes can have serious consequences for crop yield. • The plants’ response to temperature stress depends on genetic constitution of the plant, the timing of the stress during plant development, and the duration and the magnitude of the stress. The Temperature Factor Ph ot os yn th et ic R at e (g C O 2 m -2 h- 1 ) Cellular responses in freezing-sensitive and tolerant plants: • In cells that are not acclimated, the membrane is damaged by encytotic vesiculation while in acclimated cells membranes are preserved as exocytotic extrusions. • After thawing, cell expansion causes lysis of the membrane in cells that are not acclimated, but in acclimated cells after thawing, the extrusions permit expansion of the cell. The Temperature Factor 5°C 5°C 25°C 5°C 5°C • Acclimation or cold hardening - tolerance to low temperatures can be achieved if plants are hardened at low temperature prior to exposure. Solutes, including sugars, certain proteins, and amino acids, accumulate at temperatures just above freezing. • Sugars that accumulate in the vacuole decrease the amount of ice formed. • Sugars may also protect the cell against freeze-induced dehydration. Water soluble carbohydrate accumulation in roots and shoots of spring wheat, winter wheat, and spring x winter crosses. (Equiza et al., 1997) The Temperature Factor • Low temperature stress during vegetative development causes reduced plant population and/or a reduction in branching or tillering. • Freeze or frost damage at the 2-leaf stage in spring barley, if severe, will cause chlorosis of the plant. The plants will recover the green color but will produce less grain than expected. Frost-damaged barley seedlings (top) frost-damaged spikes in wheat (bottom) and frost-damaged pods in peas (right). The Temperature Factor • Gradual increase in temperature permitted maize plants to acclimate to high temperature stress. Plants that were acclimated had greater photosynthesis at the same temperature than those exposed to a rapid increase in temperature. • Inhibition of photosynthesis was not related to stomatal closure as transpiration was increased in proportion to increased temperature. □ = Gradual exposure to heat ○ = Rapid exposure to heat (Crafts-Brandner and Salvucci, 2002) The Temperature Factor • Night temperatures (greater than 20°C) adversely affect pollen development in tomato, common bean, cowpea, cotton, rice, Russian wildrye and sorghum. • High night temperature reduces the number or seeds or fruit produced. Reductions reach 50% at 26°C in cowpea. Cowpea plants will tolerate 50°C in the daytime. The Temperature Factor • The effect of high temperatures during flowering and pod development were measured over a 30-year period near Pendleton Oregon. • Pea is very sensitive to high temperatures and will die when 35°C is exceeded. • Maximum daily temperatures below 26°C had no effect on fresh pea yield in eastern Oregon. Daily temperatures above 26°C depressed yield in an exponential manner. 0 10 20 30 40 50 60 70 80 20 25 30 35 40 Maximum Temperature (C) Yi el d Re du ct io n (k g/ ha /C ) 26°C High temperature effects during flowering and pod development on yield of green peas (Pumphrey and Ramig, 1990) The Temperature Factor