Whole Plant Photosynthesis, Development, and Carbon Partitioning in Potato as a Function of Temperature

Knowledge of temperature effects on whole canopy photosynthesis, growth, and development of potato (Solanum tuberosum L.) is important for crop model development and evaluation. The objective of this study was to quantify the effects of temperature on canopy photosynthesis, development, growth, and partitioning of potato cv. Atlantic under elevated atmospheric CO2 concentration (700 mL L 21 CO2). Potato plants were grown in day-lit plant growth chambers at six constant day/night temperatures, (12, 16, 20, 24, 28, and 32 C) during a 52-d experimental period in 1999 in Beltsville, MD. Main stem length andmain stem expanded leaf number weremeasured nondestructively at 4 d intervals while leaf, stem, root, and tuber weights were obtained by destructive harvesting at biweekly time intervals. Canopy level net photosynthesis (PN) was obtained from gas exchange measurements. The optimum temperature for canopy photosynthesis was 24 C early in the growth period and shifted to lower temperatures as the plants aged. Total end-of-season biomass was highest in the 20 C treatment. End-of-season tuber mass and the ratio of tuber to total biomass decreased with increasing temperature above 24 C. Accumulated biomass was a linear function of total C gain with a common slope for all treatments. However, the proportion of C allocated to tubers decreased with increasing temperatures. High respiration losses decreased total C gain at higher temperatures. When simulating photosynthesis and C assimilation in crop models, source–sink relationships with temperature and photosynthesis need to be accounted for. POTATO is very sensitive to high temperatures. Temperatures of 31/298C (day/night) in growth chambers reduced total plant dry matter by 44 to 72% after 4 wk compared to a 19/178C regime (Lafta and Lorenzen, 1995). Tuber weights were reduced relatively more than plant dry matter. Superoptimal temperatures resulted in taller plants with high stem dry weight and smaller leaves (Lafta and Lorenzen, 1995; Prange et al., 1990), and reduced tuber production for most cultivars (Ben Khedher and Ewing, 1985; Levy, 1986). Manrique and Bartholomew (1991) reported a negative correlation between minimum temperature and the ratio of tuber to total dry weight in a study that used elevation to control temperature. High temperatures extend the period of leaf growth, which ostensibly reduces net translocation of carbohydrates to the tubers (Marinus and Bodlaender, 1975). Physiological leaf aging is also increased at high temperatures (Menzel, 1985) accelerating leaf senescence and reducing the photosynthetic capacity of the canopy. The optimum temperature for leaf photosynthesis in potato has been reported to be about 248C (Ku et al., 1977) and leaf photosynthetic rates rapidly decrease with increasing temperature (Wolf et al., 1990; Leach et al., 1982). Decreased leaf photosynthesis rate at high temperature is believed to be largely due to reduced efficiency in photosystem (PS) II rather than increased maintenance dark respiration or decreased leaf area (Prange et al., 1990). Accordingly, Thornton et al. (1996) did not find a relationship between dark respiration rates (leaf level) and biomass at harvest. Prange et al. (1990) further hypothesized that the decrease in tuber production was due to a reduction in tuber initiation resulting in a smaller sink for photosynthates. Research by Lafta and Lorenzen (1995) seems to support this view that the reduction in numbers of tubers at high temperature and concomitant reduction in sink strength reduce photosynthesis. Heat stress effects on photosynthesis in cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) have also been attributed to a decrease in the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) via inhibition of Rubisco activase (Law and Crafts-Brandner, 1999). Temperature also affects development rates of potato. The maximum development rate of potato has been reported to be within the range of 14 to 228C (Driver and Hawkes, 1943; Yamaguchi et al., 1964; Marinus and Bodlaender, 1975; Sands et al., 1979). As temperatures increase to about 228C, the development phase from emergence to tuber initiation shortens (Kooman et al., 1996b). At higher temperatures, the time to tuber initiation increases (Ewing and Struik, 1992). Detailed quantification of the effects of temperature on dry matter production and C partitioning is important to develop simulation models of potato as tools for growers to use in crop management. There are a number of potato models available (Wolf and van Oijen M. 2003; Hodges et al., 1992; Ingram and McCloud, 1984). The temperature dependencies used in these models have largely been developed from data collected in field trials and greenhouses (Ingram and McCloud, 1984), and using temperature gradients with altitude (Manrique and Bartholomew 1991). In all these cases, variations in temperature are reduced but there is no true control of temperature. Although there have been detailed measurements on C partitioning as a function of temperature (Ingram and D. Timlin, V.R. Reddy, and D. Fleisher, USDA-ARS-PSI, Crop Systems and Global Climate Change Lab., Bldg. 001, Room no. 342, BARC-W, 10300 Baltimore Ave., Beltsville, MD 20705-2350; S.M. Lutfor Rahman, Texas A&M Univ., 17360 Coit Road, Dallas, TX 75252; J. Baker, USDA-ARS Cropping Systems Research Lab., 302 West I-20 Big Spring, TX 79720; and B. Quebedeaux, Univ. of Maryland, Dep. of Natural Resources Sciences and LandscapeArchitecture, Plant Science Bldg., Room 2130, College Park, MD 20742. Received 8 Sept. 2005. *Corresponding author ([email protected]). Published in Agron. J. 98:1195–1203 (2006). Potato doi:10.2134/agronj2005.0260 a American Society of Agronomy 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: CER, carbon exchange rate; DAE, days after emergence; PAR, photosynthetically active radiation; PN, net photosynthesis; PPFD, photosynthetic photon flux density; PS II, photosystem II. R e p ro d u c e d fr o m A g ro n o m y J o u rn a l. P u b lis h e d b y A m e ri c a n S o c ie ty o f A g ro n o m y . A ll c o p y ri g h ts re s e rv e d . 1195 Published online August 3, 2006