Short-term High Temperature Effects on Stomatal Behaviors of Rice Plants. I. Occurring at the Vegetative Stage'

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1 Jur. Agric, Res. China (J:f:tMfff) 4(2) : (1991) 233 Shrt-term High Temperature Effects n Stmatal Behavirs f Rice Plants. I. Occurring at the Vegetative Stage' Chwin-Ming Yang2 and James L. Heilman" Abstract: In this study, the effects f a shrt perid f high temperature (35 C, 8 days), relative t 25 C, ccurring at the vegetative stage (Leaf 7 stage) n the seasnal changes f stmatal mvements f rice plants (Ory'za sativa L.) were investigated under cntrlled envirnment. The diurnal variatins f stmatal pattern during the curse f temperature changes were als mnitred. The physilgical imprtance f such effect was evaluated and discussed. Stmatal diffusive cnductances f 35 C-treated plants were significantly higher than 25 C during the curse f treatrnent, thugh the diurnal pattern f stmatal variatins f bth treatmints was bserved. Instead f the phenmenn knwn as midday partial stmatal clsure, the maximum cnductance ccurred at abut nn (14 h). Effect f temperature treatments may prlng up t Leaf 13 stage, which can be clearly discerned by pltting the data at 8, 14 and 2 h. Stmatal cnductance declined after heading as plants aged. Key wrds: high temperature effects, stmatal behavir, rice, Oryza sativa L. vegetative stage, cntrlled envirnment. Intrductin Stmatal mvements are directly affected by temperature, an enverinmental variable that greatly cmtributes t the grwth, develpment and yield f plants. Changes f temperature may influence water relatins f guard cells, which alng with slute exchanges and mechanical interactin between guard cells and neighbring cells gvern the pening and clsing f stmata (Willmer, 1983). Indirectly, increase f temperature may affect internal crabn dixide cncentratins, caused by the utpace f respiratin ver phtsynthesis, and the leaf-air vapr pressure deficit, resulting in plant water stress, that in turn affect stmatal mvements. Since the majr rle f stmata is t cntrl entry f carbn dixide fr phtsynthesis and t allw exit f water vapr in the prcess f transpiratin, it is expected that the 1. Cntributin N frm Taiwan Agricultural Research Institute (TARn. Part f this wrk was a prtin f senir authr's Ph.D. dissertatin. 2. Agrnmist, Department f Agrnmy,TARI, Wufeng 4131, Taichung, Taiwan, ROC. 3. Assciate prfessr, Department f Sil & Crp Sciences, Texas A&M University.Cllege Statin, Texas 77843, USA.

2 234 Jur. Agri, Res. China 4 (2) 1991 behavir f stmata in a leaf can affect the phtsynthetic rate if water is nt limited. Althugh Cwan and Farquhar (1977) have suggested that stmata may ptimize gas exchange by maintaining a cnstant rati f water lss against carbn assimilatin, thisbalance mav be jepardized by an impact f high temperature. As temperature be raised, stmatal aperture will be stimulated due t the increase f the metablic activity within the guard cells and the leaf as a whle. Beynd the range f ptimal temperature stmata pening reduced as cell damage ccurs. Taniyama et ale (1987) reprted that stmatal aperture f all cultivars f the tested rice plants reached a maximum. at abut midday bth at active tillering stage and panicle initiatin stage. Whereas, Ishihara and Saith (1987) and thers (Tenhunen et al., 1987; Turner et al., 1978) have identified a midday depressin f leaf gas exchange, especially'in a ht, dry fine day and t thse plants that are regularly subjected t drught. Yang and Heilman (199b) bserved a diurnal change f stmatal mvements in the leaves f rice plants grwn under cntrlled envirnment. Few researches have yet mnitred the diurnal variatins f stmatal mvements f rice plants during the curse f heat stress. Als, there is little infrmatin n the effect f a shrt-term high temperature, ccurring at either vegetative r reprduvtive phase, upn the seasnal changes f stmatal behavirs in rice plants. A serise f experiments were cnducted in this study t examine the crrelatins between high temperature and stmatal mvements in well-watered rice plants. The impact f a shrt perid f heat stress t the lng term stmatal behavirs was als investigated. This paper is emphasized n such effects impsing at the vegetative stage. Materials and Methds Plants f rice variety Lemnt (Bllich et al., 1984, 1985) were grwn in paque plastic cntainers (.25m diameter,. 2 rn height,.49 m" surface area), filled with fritted clay. Three plants were grwn per pt, with even space, and irrigated with nutrient slutins (see Yang and Heilman, 199a). The plants were irrigated in excess twice a day, early mrning and late afternn, t keep the sil saturated. They were flushed with distilled water, every 7 days during the vegetative grwth phase and every 3 days during the reprductive grwth phase, t avid salt accumulatin. The pts were plugged in the center s that extra water was drained frm the sil after irrigatin. The rice plants were grwn as grups in a cntrlled-envirnment grwth chamber with circulated ambient air (day/night temperatures 3 C/2 C ; relative humidity 55-7%/951%; C2 cncentratin ppmr.the daylength was 12 hurs (8-2 h) with a PPFD (phtsynthetic phntn flux density) f abut 68 tlmle n1-2 s". Wind speed was abut.8 m s '. They were rtated peridically t ensure unifrmity within the chamber. When reaching the leaf 7 (L7) stage, plants were mved t an assimilatin cabinet fr 8-day temperature treatments (25C and 35 Cl.and then returned back t the grwth chamber and grwn t maturity. The assimilatin cabinet was set fr a phtperid f 12

3 Shrt-term High Temperature Effects n Stmatal Behavirs f Rice Plants. I. Occurring at the Vegetative Stage 235 hurs (8-2 h) and cnstant day/night temperatures (25C/25C r 35C/35C) and abslute humidity. Average wind speed was abut 1 m s". The average value f PPFD at the tp f the cabinet, abut 13 j.tmle m" s", was prvided by 'Ceramalux' lamps (Philips Crp., NJ; 4 W). Air timperature was measured by a dry- and wet-bulb psychrmeter, which was placed adjacent t plant canpy and was cntrlled within ± C. The leaf stage (plant age) was assessed by the emergence f the primary leaf n the main culm (Yshida, 1981). Fr example, when the 8th primary leaf emerges frm the main culm; the plant is said t be at leaf 7 (L7) stage. Heading stage is the time perid frm the first day t the seventh day frm heading; the R-1 (R1) stage is the time perid frm the 8th t the 14th day frm heading, and s n. Stmatal (leaf) diffusive resistance was measured in the middle prtin f the yungest fully expanded primary leaves by a parameter (MK3, Delta-T Devices, England). Fr diurnal data, -the first measurement was taken at 8 h, the nset f phtperid, and the measurements were cntinued every tw hurs until 2 h, the end f daytime hurs. Stmatal cnductance, the inverse f stmatal resistance, was used fr analysis thrughut this study. The mean values and standard deviatins were taken frm the averages f each grup;at least fur grups fr each mean value. Results When plants were transferred frm the grwth chamber (day/night temperatures 3 C /2 C) t the assimilatin cabinet (25 C/25 C), stmatal cnductances declined until the fifth day f treatment (Figs. 1 and 2) as a result f changing grwth. Hwever, a reversed result was shwn until the fifth day when plants were transferred t high temperature (35 C/35 C) cabinet (Fig. 2). There were cnsiderable differences f stmatal cnductance between the tw temperature levels. Nevertheless, diurnal variatins f stmatal cnductance were bserved in bth treatments thugh data frm 25 C were less distinctive than 35 C. Cnductance was greatest at abut 14 h, the middle f phtperid, during the treatment perids. Mnitring f the diurnal variatins f stmatal cnductance after the treatments, frm Leaf 8 stage t R-4 stage (Figs. 3 and 4), shwed that temperature effects between treatments may extend up t Leaf 13 stage. This result is mre clearly discerned frm the cnductances measured at 8, 14 and 2 h as a functin f stage f develpment as shwn in figs. 5, 6 and 7. It was als shwn that stmatal diffusive cnductances declined after heading as plants aged.

4 236 J ur. Agri, Res. China 4 (2) Leaf 7 ụ., (f) -, E -.c:;.., c u ;:l " c u Time Fig 1. Stmatal cnductances f Primary leaf 7 measured in the grwth chamber (day/night tem peratures 3 C/2 C) at the Leaf 7 stage. T he measured primary leaf was the yungest fully expanded leaf. Standard deviatin is included. 4 day 1 day 2 day 3 day 4 day G - 25 C 3.., u c u ;:l " C < Time Fig 2. Effects f temperature treatments (35 C and 25 C) at the Leaf 7 stage n the diurnal changes f stmatal cnductances f the 7th primary leaf. The measured primary leaf was the yungest fully expanded leaf. Standard deviatin is included.

5 Shrt-term High Temperature Effects n Stmatal Behavirs f Rice Plants. I. Occurring at the Vegetative Stage Leaf 8 1 Leaf 1 Leaf C -25C 7 \...'.-' ;-. (,) Cl) Leaf 11 1 S.:'..... t.. 1. <l,; e (,) c:: r ::s c:: Leaf 13 Leaf 15 Leaf C -25 C (/) -, '-'" Leaf 12. U Leaf Time Fig 3. The diurnal changes f stmatal cnductances f the primary leaves 8 t 16 as affected by 8-day temperature treatments impsed at the Leaf 7 stage. The measurements were taken at the crrespnding stages. Standard deviatin is included. 237

6 238 J ur. Agri, Res. China 4 (2) U Q) Ul -, s A ( I r Leaf C - 25 C Heading R-1 At,n,. (1':' y. Q) c 5 ;:l " c:: 1 R C - 25 C R-3 R-4 " ' I. «,......\ j l-,... '..." Time Fig 4. The diurnal changes f stmatal cnductances f the 17th primary leaf at the leaf 17, hea ding, the R-1,t he R-2, the R-3, and, the R-4 stages, as affected by 8-day temperature treatments impsed at the Leaf 7 stage. Standard deviatin is included. 1 At 8 h C U Il) - 25 C -, '" E -.3 e, -. ' "..,.., Il).... u.., c «l... u ;:l ' " c U H R1 R2 R3 R4 Leaf Stage ( Plant Age) Fig 5. Stmatal cnductances at 8 h as functins f temperature and leaf stage (plant age).

7 Shrt-term High Temperature Effects n Stmatal Behavirs f Rice Plants. 239 I. Occurring at the Vegetative Stage 2. At 14 h U 1 Q) (/'J -, S <;» C --25 C H Rl R2 R3 R4 Leaf Stage ( Plant Age ) Fig 6. Stmatal cnductances at 14 h as functins f temperature and legf stage (plant age). 1 At 2 h u en -, e C --25 C u es u ::J ' u H m R2 R3 R4 Leaf Stage ( Plant Age ) Fig 7. Stmatal cnductances at 2 h as functins f temperature and legf stage (plant age).

8 Jur. Agri, Res. China 4 (2) Discussin Diurnal changes f stmatal mvements were bserved in rice plants under cntrlled envirnment, Whereas, stmatal pening was stimulated at 35 C thugh diurnal patterns were preserved. This behavir is similar t rice grwn under natural cnditins (Tenhunen et al., 1987) and als fr field-grwn rice varieties (Kawamitsu and Agata, 1987; Ishihara and Saith, 1987). As Willmer (1983) pinted ut, increased stmatal cnductance due t high temperature may enhance gas exchanges in favr f phtsynthesis and evaprative cling f the leaf and imprve the transpiratin stream fr in uptaks and transprt. Hwever, the demand fr metablic activities, the lss f water in increasing transpiratin rate, and the damage t cells and grwing prcesses may ffset the advantages and result in a detrimental effect, especially when such heat stress is prlnged. The relatinship between leaf cnductance and net phtsynthesis is clsely crrelated ( Wng et al., 1979; Krner et al., 1979). Frm linear regressin, a clse crrelatin between stmatal cnductance and phtsynthetic rate was fund in rice plants (Kawamitsu and Agata, 1987). The same cnclusin \vas als made by thers (Ishihara and Saith, 1987; Ishii et al., 1977). Mre wrks, hwever, need t be dne t elucidate increase f stmatal cnductance in relatin t the cunterbalance f phtsynthesis and respiratin during treatment perid. The phenmenn knwn as midday stmatal clsure "vas nt bserved in this case, which may be due t a well-watered plants and the cntrl f abslute air humidity in the grwth chamber. Taniyarna et ale (1987) reprted similar results in the tested rice cultivars, while Ishihara and Saith (1987) shwed that leaf stmatal aperture f rice plant decreased in fine day with high evaprative demand under submerged cnditin in the field. Effects f 8-day temperature treatments n stmatal behavir was fund t extend up t leaf 13 stage. The result was mre clearly discerned at 8, 14 and 2 h. Whether such effects have a significant impact upn grwth and develpment f rice plants needs t be further studied. The decrease f cnductances after heading is n surprise since the senescence f the measured leaf as well as plant canpy was in prgress. References 1. Bllich, C. N., B.D. Webb, M.A. Marchetti, J.E. Sctt and J.vV. Stanesl Lemnt characteristics and perfrmance, In : The semidwarf-a New Era in Rice Prductin. p The Texas Agric, Exp, Sta., Cllege Statin,Texas, USA. 2. Bllich, C.N.. B.D. Webb, M.A. Marchetti, and J.E. Sctt Registratin f Lemnt rice. Crp Sci. 25 : Cwan, I.R. and G. D. Farquhar Stmatal functin in relatin t leaf metablism and envirnment. In : Integratin f Activity in the Higher Plant. Sc. Exp. 'Bil. Symp. 31: Ishihara, K, nad K. Saith Diurnal curses f phtsynthesis, transpiratin, and diffusive cnductance in the single-leaf f rice plants grwn in the paddy field under submerged cnditin. Japan. J. Crp Sci. 56: 7-17.

9 Shrt-term High Temperature Effects n Stmatal Behavirs f Rice Plants. I. Occurring at the Vegetative Stage Ishii, R., R. Ohsugi and Y, Murata The effect f temperature n rates f phtsynthesis, respiratin and the activity f RuDP carbxylase in barley, rice and maize. Japan. J. Crp Sci. 46 : Kawarnitsu, Y. and W. Agata, Varietal differences in phtsynthetic rate, transpiratin rate and leaf cnductance fr leaves f rice plants. Japan. J. Crp Sci. 56 : Krner, C., J. A. Scheel and H. Bauer Maxirnurn leaf diffusive cnductance in vascular plants. Phtsvn thetica 13: T'anivarna, T., M. L. N. Ra, S. V. Subbauah and K. Ikeda Cultivatin and ecphvsilgy f stmatal aperture in S111e rice cultivars f India. Japan. J. Crp Sci. 56:226-23l. 9. Tenhunen, J. D., R.vV. Pearcy and O.L. Lange Diurnal variatins in leaf cnductance and gas exchange in natural envirnments. In : Stmata Functin. p E. Zeiger, G.D. Farquhar and 1. R. Cwan, eds. Stanfrd University Press, Stanfrd, Califrnia. 1. Turner, N. C., J. E. Begg, H. 1\1. Ra-wsn, S. D. English and A. B. Hearn Agrnmic and physilgical respnses f sybean and srghum crps t water deficits. III. Cmpnents f leaf water ptential, leaf cmductance, 14 C2 phtsynthesis, and adaptatin t water deficits. Aust. J. Plant Physil. 5 : Willmer, C. M Stmata. p, Lngman, Lndn. 12. Wng, S. C., 1. R. Cwan and G. D. Farquar Stmatal cnductance crrelates with phtsynthetic capacity. Nature 282 : Yang, C-M. and J. L. Heilman. 199a. Study f leaf area as functin f age and temperature in rice i.orsza sativa L.). J. Agric, Res. China 39 : Yang, C-M. and J. L. Heilman. 199b. Diurnal and seasnal stmatal behavirs f rice plants grwn in cntrlled envirnment. Chinese Agrn. J. 1 : Yshida, S Fundamentals f rice crp science. p Internatinal Rice Research Institute. Ls Bans, Philippines.

10 242 Jur. Agri. Res. China 4 (2) 短期高溫處理對水稻氣孔表現之效應. 楊純!tJ I. 營養生長時期 1 James L. Heilman 3 摘要本文旨在控制環境下探討水稻 ( O r)切 sa tiva L.) 營養生長期間短期高溫處理(35 C 8天 ) 後氣孔運動之季節性表現並調查處理期間氣孔每日週期性變化以瞭解和評估高溫對水稻氣孔行為及生理上之影響結果顯示高溫雖然提高氣孔傳導度但不影響其每日週期性變化氣孔傳導度在中午達到最高點因此所謂午間氣孔部份關閉現象並未發現結果亦顯示營養生長初期(第 7葉齡期 )短期的天)溫度處理之效應可達至第 1 3葉齡期至幼穗形成期時氣孔傳導度顯著升高此一結果可能為植株追求高光合成需要所產生之自身調節且不受第七葉齡期短期高溫處理之影響本試驗同時證明水稻葉片在控制環境下具有氣孔運動 ' Oryza 關鍵詞:高溫處理氣孔行為水稻 sativa L. 營養生長期間控制環境 1.臺灣省農業試驗所研究報告第 1 574號 2. 本所農藝系副研究員臺灣省臺中縣霧峰鄉 3. 美國德州農工大學土壤暨作物系副教授美國德州大學城

Study of Leaf Area as Functions of Age and Temperature in Rice (Oryza sativa L.) 1

Jour. Agri, Res. China ($J!Uff) 39(4) : 259--268 (199) Study of Leaf Area as Functions of Age and Temperature in Rice (Oryza sativa L.) 1 Chwen-Ming Yang" and James L. Heilman" Abstract: Correlations between