Asian Journal of Sciences 7 (I): 67-72, 2008 ISSN 1682-3974 O 2008 Asian Network for Scientific Information

Adaptation of Growth and Respiration of Three Varieties of to Environmental Temperature

'Weili Yu, 3Lee D. Hansen, 'Wenying Fan, 'Wenyi Zhao and 4E.Durant McArthur 'College of Soil and Water Conservation, Beijing Forest University, Beijing 100083, China 'Inner Mongolia Academy of Forest and Science, Huhhot, Inner Mongolia 010010, China 3Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA 4USDA Forest Service, Rocky Mountain Research Station, Shrub Sciences Laboratory, Provo, Utah 84606, USA

Abstract: Growth and respiratoIy characteristics of Caragana korshinskii from Wushen and two dfferent seed sources of C. davazamcii from Hehnger and Yimhuole, all grown at the same conditions, were determined by measuring metabolic heat and CO, production rates by isothermal calorimetq at 5°C intervals from 10 to 40°C. Substrate carbon conversion efficiencies and growth (anabolic) rates were calculated from the measured data. Differences in substrate carbon conversion efficiency, respiratoIy rates and temperature responses of respiratoIy rates among the three accessiom all contribute to produce dffering temperature responses of growth rate. Planting seeds from these seed sources outside their native ranges will probably not be successful because of the differences in temperature adaptation.

Key words: Wushen Caragana korshinskii, Yijmhuole Caragana davazamcii, Helinger Caragana davazamcii, substrate carbon conversion efficiency, CO, production rate, metabolic heat rate,

INTRODUCTION vegetation. C. korshinskii is a species of the southern Alashan and western Ordos where it occurs in fixed and Temperature is one of the most significant semi-fixed dunes of the steppe desert and the typical determinants of plant distribution. adapt their desert zone. The zonal distribution of Caragana forms an growth to their niche by adapting their respiratoIy obvious geographc substituted dstribution from east to metabolism to the temperature pattern of the environment west or from nohto south (Zhao, 2005). C. korshinskii (Criddle et al., 2005). Altering rates and the temperature and C. davazamcii are distinguished by characteristics dependence of metabolism and metabolic efficiency of flowers, seeds, leaves and especially bark and height. may all be impomnt in adapting growth characteristics C. korshinskii has yellow-gold, lustrous bark and to the local climate. This study compares growth and grows taller (300-500 cm, Zhao, 2005) than C. davazamcii respiration characteristics of Caragana korshinskii (50.1 50 cm, Zhang et al., 2002). The morphology of leaves from Wuhen and C. davazamcii from Helinger and of Caragana show a regular geographic gradent, leaf Yijinhuole, Inner Mongolia. These shrubs are used for area becomes smaller and well developed palisade tissue combating desertification, for water and soil conservation in the intercellular space also tends to become smaller (Zhang et al., 2002; Niu, 2002), as feed for cattle and from east to west (Yan et al., 2002). Drought tolerance wild animals in deserts and grasslands and are the also increases from east to west. There are main shrub used for rangeland restoration in Inner disagreements on the of C. davazamcii and Mongolia. C. korshinskii; Sanchir (1 974), Fu (1977), Liu (1 984) and C. korshinskii and C. davazamcii are dstributed Zhao (1990) argue that they are independent species, from the west to the middle of Inner Mongolia. Yakovlev (1988) argues that they are the same species and C. davazamcii is a species of the eastern Gobi, occurring Zhang and Zhu (2004) argue that C. davazamcii is a in the steppe desert and desert steppe zones on sand variant of C. korshinskii For nomenclature purposes lands and Loess hlls of the Ordos Plateau and nohern only, in th~sstudy C. korshinskii and C. davazamcii are Loess Plateau where it is a dominant species of shrub considered to be independent species.

CorrespondingAuthor: Lee D. Hamen, Chemisby ClOOBNSN, BYU, Provo, Utah 84602, USA 67 Asian J. Plant Sci., 7 (1): 67-72, 2008

In this study, CO, production rates (Rco,) and C, = Carbon substrate which is assumed to be metabolic heat rates (R,) are measured as a function of carbohydrate in this reaction as written temperature by calorespirometry on young, growing leaf C,,, = New growth, ie, the rate of formation of C,,, is tissue of C. korshinskii and C. davazamcii. These data equal to the rate of growth or development allow calculation of growth (or anabolic) rates and substrate carbon conversion efficiencies as functions of Heat energy stored in ATP by the catabolic reaction temperature. Selection of accessions for restoration can is released in the anabolic reaction, but because the ATP then be done by matching growth respomes to local reactions cancel in the overall process, th~sheat can be temperature patterns to maximize the hkehhood of assigned to either reaction and the calculations are greatly success. Ths 1aboratoIy method cannot completely simplified if it is assigned to catabolism. replace field experiments, but can save much time and The sum of the catabolic and anabolic reactions is: effod and make field experiments much more efficient. Determining the relationshp between metabolism and C, + aO, + (N,P,K, etc.) - FC,,,+(~-F)CO, (3) growth and thence the mechanism of adaptation of different accessions to environmental temperature Where, F is the substrate carbon conversion patterns will provide better understanding for use of efficiency, ie, the fraction of C, converted to C,,,. these shrubs. Equations relating mass-specific growth (anabolic) rate (R,,) to F and to measured Rco, and R, have been MATERIALS AND METHODS derived (Hansen et al., 2005, 2004);

This study was conducted at the Shrub Sciences R,JRco, = ~/(1-F) or R,, = Rco, [d(1-F)] (4) LaboratoIy of the USDA Forest Service and the and Depament of Chemistry and Biochemistry of Brigham Young University, both inProvo, Utah, USA.

Theory: Plant growth depends on photosynthesis to Where, AH, and AHco, are, respectively, enthalpy supply substrate carbon, but under many conditions the changes for the difference in heats of combustion of limiting factor for growth is not photosynthate, but substrate and biomass and for the heat of combustion of micronutrients andor the rate of utilization of substrate to CO,. For closely related tissues, AH, can be photosynthate by respiration (Vitousek and Howah, regarded as a comtant and for vegetative tissue similar to 1991; Hansen et al., 1998). Fder,because the processes that used in this study, can be assumed equal to +30 kJ of photosynthesis and respiration are separated in time, Cmol-' (Lamprecht 1999). From Thornton's ~ule,AHco, is photosynthesis rate cannot be used to predxt growth approximately equal to -455(l -y,/4)kJ Cmol-' where y, is rate. However, growth rate of vegetative tissue is equal to the chemical oxidation state of carbon in the substrate the anabolic rate in respiration and calorespirometry can (eg, for carbohydrate y, = 0, for lipid y, = -1.8 and for be used to obtain both the anabolic and catabolic rates protein y, = -1.0). Specifically for carbohydrate, and thus the growth rate and substrate carbon conversion AHco, is -470 kJ Cmol-I; so in the absence of efficiency (Hansen et al., 2004, 2005). Catabolism of evidence for other substrates, AHco, is assumed equal to photosynthate provides the energy to drive anabolism -470 kJ Cmol-I. and anabolism produces structural biomass from Combining Eq. 4 and 5 to eliminate R,, gives an photosynthate. Because nearly all of the heat of equation for F respiration is produced by catabolism, the metabolic heat rate (R,) measures the rate of catabolism;

C, + 0, + xADP + xPi - CO, + H,O + xATP +heat (1) Determination of anabolic and catabolic rates and F Where, C, is the carbon substrate (assumed to be as functiom of temperature for different genotypes grown carbohydrate in this reaction as written). ATP generated under the same condtions allows determination of the during catabolism supplies energy to drive anabolism, influence of genotype and thus of natural selection by environmental temperature on these characteristics.

Materials: Seeds of Caragana korshinskii were collected Where: near and Nohwest of Wushen, Inner Mongolia and Asian J. Plant Sci., 7 (1): 67-72, 2008

Table 1: Results of linear least squares fitting (Excel, linest function) of plots of avmge values of Rco, versus % at 10, 15, 20, 25, 30, 35 and 40°C. Uncertainties are given as the standard deviation Elevation RJRco, Rco, Intercept Cm. Substrate carbon Species Origin Location (m) (kJ mol-I) (pmol seccl mg-? coeff R2) conversion efficiency (8') Cmqwakorslunrkii Wushen 38" 42'N 108" 40'E 1307 377+16* 0 1i0.9 0.991 075* Cmqmdwarmcii Yijinhuole 39' 34'N 109' 47'E 1329 429+26 2.4i1.8 0.981 0.58 Cmqmdwarmcii Hellnger 40°26'N 111" 50'E 1522 440+17 1.8t0.9 0.992 0.50 ": The substrate carbon conversion efficieno e was calculated with eauation 6 assuming AHco, = -470 kJ Cmol-I and AH, = +30 kJ CmolP, *: Indicates these values differ significantly from the others in the column

seeds of Caragana davazamcii were collected near obtained after drying the samples for 24 h in a vacuum Helinger and east Yimhuole, Inner Mongolia (Table 1). oven at 70-80°C. Metabolic heat and CO, rates were Seeds were planted in small containers with potting soil divided by the dry weights to obtain mass-specific rates. and grown in a greenhouse to a seedling height of 10-15 cm. Stems with attached leaves from the top branch RESULTS were used for the calorespirometric measurements. Figure 1 and 2, respectively show the average heat Measurement method: HaJt Scientific Model 7707 and and CO, production rates versus temperature. These plots Calorimetq Sciences Corporation Model 4100 are not linear when plotted on Arrhenius axes, ie, h(rate) calorimeters, each with three 1 mL sample and one versus reciprocal absolute temperature. The metabolic reference ampule, w ere used in isothermal mode. heat and CO, rates have similar responses to temperature, Seventy to 110 mg fresh tissue was placed into a sample but the responses differ among the three accessions. At ampule and the ampule inserted into the calorimeter. The temperatures below 25T, R, and Rco, of the three calorimeter was set to a selected temperature and allowed accessions are comparable. At temperatures above 25T, to equilibrate for 20-30 min to obtain a steady-state R, and Rco, of Yijinhuole are hgher than those of metabolic heat rate which was obtained during the last Helinger, which are higher than those of the Wushen 5-10 min of this period. The ampule was then taken out variety. and a 40 pL vial of 0.4 M NaOH placed in the ampule with To determine whether the substrate carbon the tissue, the ampule was replaced in the calorimeter and conversion efficiency (F) changed with temperature, plots the heat rate measured again. The heat rate from th~s of Rco, versus R, were constructed and fit to a linear second measurement is the sum of metabolic heat and equation by least squares. The results are shown in heat from NaOH reacting with CO,, Table 1. If such a plot is linear and has a zero intercept, it

CO, (g) + 20H-(aq) = CO, '-(aq) + H,O(aq) AH = -108.5 kJ mol-' (7)

After removing the vial of NaOH, the metabolic heat rate is measured again. The metabolic heat rates from the first and third measurements are averaged and subtracted from the heat rate from the second measurement to obtain the heat rate for formation of carbonate (in pW or pJ sec-I). Dividmg th~srate by 108.5 pJ nmol-' gives the production rate (Rco,) of CO, in nmol set-I. Averaging the two measurements of metabolic heat rate corrects for any small drift in the rate during the measurement period. This Temperahm (DC) protocol was repeated at 10, 15, 20, 25, 30, 35 and 40°C for each seed source. A given tissue sample was Fig. 1: Metabolic heat rates (pW or pJ sec-' mg-' dry measured in sequence at 20, 15 and 10°C, at 20, 25 and weight) of leaf tissue from Caragana korshinskii 30°C, or at 30, 35 and 40°C. To verify that sample hstory from Wushen (WNJ) and C. davazamcii from had no effect addtional samples were measured at only Helinger (HXJ) and from Yimhuole (YXJ), Inner one temperature. Because the calorimeters measure the Mongolia. Error bars show the 95% confidence heat rates from three samples simultaneously, there were intervals. The scatter is largely due to dffering three to nine replicates for each species and seed source, respomes of tissue samples since the instment with each ampule being a unit. Dry Weights (DW) were scatter is 4% Asian J. Plant Sci., 7 (1): 67-72, 2008

fiy April Msy June h Month Fig. 2: CO, production rates of leaf tissue from I Caragana korshinskii from Wushen (WNJ) and Fig. 4: Monthly average temperatures for Wushen C. davazamcii from Helinger (HXJ) and from (WNJ), Hehnger (HXJ) andYijmhuole (YXJ), Inner Yimhuole (YXJ), Inner Mongolia. Error bars show Mongolia the 95% confidence intervals. The scatter is largely due to differing responses of tissue Because it is hghly unlikely that AHco, or AH, samples since the imtmment scatter is 40% differ among the accessiom, we conclude that the substrate carbon conversion efficiency and thus the anabolic-catabolic coupling of the Wushen variety is significantly greater than the substrate carbon conversion efficiencies of the Yijinhuole and Helinger varieties. Figure 3 shows that the temperature of maximum growth rate is similar among the three accessiom, but the maximum growth rate differs. The maximum growth rate decreases in the order Yiinhuole>Wushen>Helinger, but note that total growth is propofiional to the integral of the growth rate over the temperatures and time of the growth season. These cwes show Wushen is adapted to grow at environmental temperatures from 12-43°C; Yimhuole from 18-41"C and Helinger from 5-46°C. Yijmhuole may have a second, lower growth rate maximum around 10°C. Such bimodal cwes of growth rate versus temperature have previously been found for plants adapted to climates Fig. 3: Growth rates calculated from average metabolic with large, comistent diurnal temperature variations heat and CO, production rates of leaf tissue from (McCarlie et al., 2003; Ward, 2007). In agreement with Caragana korshinskii from Wushen (WNJ) and these results, Helinger is native to the coldest region, C. davazamcii from Helinger (HXJ) and from Yijinhuole is in the middle and Wushen is native to the Yijmhuole (YXJ), inner Mongolia. The temperature warmest climate. Monthly average temperature and ranges estimated from the growth cwes indicate the range for optimal growth precipitation during the growth season are given in Fig. 4 and 5. Wushen is slightly wanner on average and

can be concluded that AHco,, AH, and F do not change the average temperatures are not significantly dfferent with temperature (Eq. 6) and thus that the substrate and between the other two sites, but averaging apparently biomass composition and catabolic-anabolic coupling do hides significant dfferences in the temperature not change with temperature over the linear range of the patterm. It is unfodate that data on high and low plot. The intercepts in Table 1 are near zero and the plots temperatures at these sites are not available to compare are linear, showing that none of these characteristics with the temperature ranges derived from the growth change significantly with temperature. cwes. Asian J. Plant Sci., 7 (1): 67-72, 2008

In conclusion, this study shows that no simple relation exists between any one respiratoIy characteristic and the growth propedies of these three accessions of closely related plants. The temperature responses of the growth rates result in similar total seasonal growth of plants of each accession when grown in the native climate, but planting seeds from these seed sources outside their native ranges will probably not be successful because of the dfferences in temperature adaptation.

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