Open access peer-reviewed chapter

Chlorophyll a Fluorescence as an Indicator of Temperature Stress in Four Diverse Cotton Cultivars (Gossypium hirsutum L.)

Written By

Jacques M. Berner, Mathilda Magdalena van der Westhuizen and Derrick Martin Oosterhuis

Submitted: 18 February 2022 Reviewed: 21 March 2022 Published: 07 September 2022

DOI: 10.5772/intechopen.104598

From the Edited Volume


Edited by Sadia Ameen, M. Shaheer Akhtar and Hyung-Shik Shin

Chapter metrics overview

58 Chapter Downloads

View Full Metrics


Heat stress has a detrimental effect on cotton (Gossypium hirsutum L.) production worldwide. The reproductive stage is especially vulnerable to heat stress, which will result in significant yield losses. Chlorophyll a fluorescence (ChlF) induction kinetics was used to investigate the heat tolerance of four cotton cultivars. Cultivars Arkot 9704, VH260, DP393, and DP 210 B2RF were subjected to 30°C and 40°C heat treatments. Plants were grown for 46 days up to the pinhead square stage whereafter plants were subjected to the two temperature regimes for a period of 6 hours. Decreases in the maximum quantum yield of PSII (Fv/Fm) and the performance indexes (PIABS and PITOTAL) reflected the negative impact of elevated temperature on photosynthesis in all four cultivars. In cultivar DP393 the lowest drop in values for Fv/Fm, PIABS, and PITOTAL, showed the genetic capacity of this cultivar to cope with heat stress. Cultivars VH260, DP210 and to a lesser extent Arkot 9704 were adversely affected by heat stress. Chlorophyll a fluorescence measurements and the interpretation of the functions within the chlorophyll transient proved to be a fast and accurate method of identifying heat-tolerant cotton cultivars.


  • chlorophyll a fluorescence
  • cotton (Gossypium hirsutum)
  • cultivar DP393
  • heat stress
  • heat tolerant

1. Introduction

Cotton, the most important and widespread natural fiber globally, is produced in 75 countries, providing income for more than 250 million people [1]. Cotton is a significant agricultural commodity throughout the world used primarily for its fibers to manufacture textiles [2]. Approximately half of all textile products are made of cotton in the form of apparel, home textiles, and industrial products [1]. Global climate changes strongly influence plant production worldwide [3]. Crop growth and productivity are severely impacted when plants experience drought and heat stress [4]. Heat stress is defined as the rise in temperature beyond a threshold level for a sufficient period of time to cause irreversible damage to plant growth and development [5]. The effects of plant stress depend on the crops’ tolerance toward stress, timing (developmental stage), duration and severity of stress [6, 7].

High temperatures (>32°C) cause serious yield reduction in cotton by affecting its physiology, biochemistry, and quality [8]. Excessive temperatures (even 1°C) significantly limit the yield formation process, decrease boll retention, and reduce yield by 110 kg ha−1. This decline in yield is attributed to smaller boll biomass and a low number of seeds produced in a boll which is caused by heat-induced pollen damage, low fertility and fertilization efficiencies [8].

Cotton is a warm-season crop, but a negative correlation was found between yield and high temperature during the reproductive stage [9, 10]. Research in Arizona and Mississippi in the United States indicates that the reproductive performance of Upland cotton declines once the mean crop temperature exceeds 28–30°C [11, 12, 13]. Excessive temperature (above 30°C) during the reproductive stage (flowering) detrimentally affects cotton yield potential [14]. Schlenker and Roberts [15] indicated that yield growth for corn, soybean, and cotton would gradually increase with temperatures up to 29–32°C and then sharply decrease with temperature increases beyond this threshold.

The thermal kinetic window (TKW) for enzyme activity in cotton (23.5–32°C) strongly correlates with optimal temperatures for general metabolism and growth for various species [16]. Photosynthesis in cotton is highly sensitive to temperatures above 35°C [17, 18, 19, 20]. Some physiological effects of high temperature include decreased efficiency of the photosystems [19, 21, 22]. In cotton, heat stress during flowering resulted in square and flower drops when day temperatures exceeded 30°C [13].

Photosynthesis is one of the processes that are sensitive to heat stress [23]. Because of its sensitivity, the plant’s photosynthetic efficiency is often measured to determine how sensitive the plant is to stress. Photosystem II (PSII) is the initial complex in the photosynthetic electron transport chain, responsible for water oxidation and the generation of molecular oxygen [24]. Heat stress causes changes in the reduction-oxidation properties of PSII acceptors. It reduces electron transport efficiency in the photosystems [25]. Heat stress causes several reactions, for example, increases in leaf senescence, reduction of photosynthesis, deactivation of photosynthetic enzymes, and generation of oxidative damages to the chloroplasts [26].

Chlorophyll fluorescence originates from chlorophyll a pigments [27]. The absorbed light energy can undergo one of three fates, namely, (a) drive photosynthesis, (b) dissipation of excess energy as heat, and (c) re-emitted as light at a longer wavelength (fluorescence). These three processes compete with each other, such that the increase in efficiency of one will lead to a decrease in the yield of the other two [27, 28]. Chlorophyll a fluorescence is defined as the loss of partial exit energy after the antennae have absorbed the light. This occurs in Photosystem II (PSII) through the radiation of red light with a wavelength of 680 nm. Therefore, chlorophyll a fluorescence is light re-emitted by chlorophyll molecules during the return from non-excited states and used as an indicator of photosynthetic conversion in higher plants.

The motivation for the study was to evaluate diverse cotton cultivars to identify a heat-tolerant cultivar. The research was done to assess whether or not chlorophyll a fluorescence is a useful method to indicate heat tolerance in a cultivar to ease breeders’ work to breed superior cultivars, capable of withstanding heat waves that are occurring more often due to climate change. The early identification of cotton cultivars tolerant toward heat stress is of great economic importance and an objective that many plant breeders prioritize. With this study on cotton, chlorophyll a fluorescence measurements are investigated as a useful tool to identify and quantify the impact of heat stress. With such data for different cultivars, negative impacts and crop losses can be avoided, ensuring more stable cotton production.


2. Material and methods

In this study, four diverse cotton cultivars, namely, Arkot 9704, VH260, DP393, and DP210 B2RF were planted in 10 pots in soil that consisted of a 50/50% mixture of coarse sand and black arcadia clay in a greenhouse study with 30/20°C day/night temperature. The pots were placed in a randomized block design. Plants were grown for five weeks up to the pinhead square stage and then subjected to heat stress. Plants were subjected to two treatments in two laboratory ovens (Scientific 2000) to create the 30°C control and 40°C heat stress. During the first study, five-week-old plants were subjected to heat stress for 2, 4, and 6 hours. During studies 2 to 4, only a 6-hour measurement was taken as this was the only treatment that showed significant differences in their chlorophyll fluorescence measurements.

Chlorophyll fluorescence measurements of intact dark-adapted cotton leaves were measured five weeks after emergence with a portable fluorometer (PEA-Plant Efficiency Analyzer, Hansatech Instruments, King’s Lynn, Norfolk, UK). One leaf per plant was measured at three different positions on the leave. The samples were dark-adapted for 6 hours before the measurements and then illuminated with continuous light (2400 μmol m−2 s−1, 650 nm peak wavelength, for 1 s provided by an array of six light-emitting diodes focused on a circle of 5 mm diameter of the sample surface. Biolyzer v.3.0.6 software (developed by R Rodriguez, University of Geneva) evaluated fluorescence induction transients. Table 1 is a summary of parameters measured via chlorophyll a fluorescence measurements, plus a description of the formulas with references to authors.

Maximum quantum yield
a quantitative measurement of maximum or potential photochemical efficiency [29]. Fv/Fm is the most widely used parameter in chlorophyll fluorescence research to document stress [3031] and [28] defined the boundary level for a fully functional PSII system to be 0.750Fv/Fm = (Fm-F0) / Fm
F0 = minimal fluorescence,
Fm = maximal fluorescence
Fv = variable fluorescence.
Butler and Kitajima [32] were the first authors to calculate the maximum quantum yield of primary PSII photochemistry (Fv/Fm) based on the characteristics of the OJIP curve. Fv/Fm was however shown to be nonspecific [33] and insensitive [34].
PIABSa multiparametric function representing three independent parameters contributing to photosynthesis, namely;
(1) the density of fully active reaction centers (RC’s); RC||,
(2) efficiency of electron movement by trapped excitation into the electron transport chain beyond QA; and
(3) the probability that an absorbed photon will be trapped by RC’s. It therefore reflects the accumulation of all of PSII’s responses:
Strasser et al., [35] developed performance index of overall photochemistry (PIABS) by using three independent OJIP curve parameters (φPo—maximum quantum yield of primary PSII photochemistry, ψEo—efficiency with which a PSII trapped electron is transferred from Q − A to PQ: and RC/ABS—the density of PSII reaction centers) [35]. PIABS could reflect the state of plant photosynthetic apparatus more accurately than Fv/Fm [36] whereas PIABS was related only to the electron transport to the PQ pool [37].
PITOTALPITOTAL (relative photosynthetic performance) (one of the most sensitive OJIP parameters) [30]. include the four partial parameters that are related to the amount of active PSII reaction centers per absorbed energy (RC/ABS), the maximum energy flux reaching the PSII reaction centers per absorbed energy (jPo/(1 – jPo)), the probability that this energy will be conserved as redox energy and drive electron transport beyond QA (yEo/(1 – yEo)), and the probability that electrons from intermediate carriers finally reach the end acceptors of PSI (dRo/(1 – dRo)). PITOTAL is considered to be positively correlated with CO2 assimilation rates, hence to productivity based on photosynthesis [38].Tsimilli-Michael and Strasser, [39], defines PITOTAL as: RC/ABS jPo/(1–jPo) yEo/(1–yEo) dRo/(1–dRo)
[40] Hao et al., 2021 summarize, PITOTAL as calculated by PIABS and δRo (the efficiency of the electron from PQH2 is transferred to final PSI acceptors), which can fully describe the photochemical activity of the linear photosynthetic electron transfer chain

Table 1.

Parameters measured plus description.


3. Results

The Fv/Fm values were significantly lower in heat stress plants than in non-stressed plants in all four cultivars. The lowest drop for Fv/Fm in values between heat stress and non-stressed plants were in the leaves of cultivar DP393, meaning DP393 coped with the heat stress and exhibits heat tolerance. The highest drop in values was in cultivar VH260, then DP210 and Arkot 9704 (Figure 1). The decreased values of Fv/Fm in heat stress plants were likely due to damage to the PSII system and a consequent increase in non-photochemical quenching (NPQ) [41]. Increasing temperature damages PSII reaction centers and dissociates antennae pigment-protein complexes from the central core of the PSII light-harvesting apparatus, consequently impairing photosynthesis [42].

Figure 1.

The effect of 6 hours of continuous heat stress on the maximum quantum yield (Fv/Fm) of four cultivars (Arkot 9704, VH260, DP393 and DP 210 B2RF) treatment values not connected by the same letters are significantly different (P < 0.05).

3.1 The difference in relative variable fluorescence (ΔVXX)

Double normalization of the OJIP curve between 0.03 ms and 2 ms reveals the presence of the ΔK-band (Figure 2). An increase in the amplitude of the ΔK-band is indicative of damage to the oxygen-evolving complex associated with photosystem II. Heat stress affected the oxygen-evolving complex much more of Arkot9704 than DP393. When ranking the genotypes according to heat tolerance using variable fluorescence, DP393 was the most heat tolerant, followed by VH260 and DP 210 B2RF, and Arkot 9704 was the most sensitive to heat.

Figure 2.

The difference in relative variable fluorescence (ΔVOJ) of cotton cultivars Arkot 9704, VH260, DP393, and DP210 B2RF after a 6-hour exposure to heat stress at 40°C (van der Westhuizen, 2017).

3.2 Performance index: PIABS

PIABS values were significantly (P ≤ 0.05) lower in the heat-stressed plants. The lowest decline in values between heat stress and non-stressed plants was in the leaves of cultivar Arkot 9704, followed by DP393, DP210. The highest difference in the values was in cultivar VH260 (Figure 3).

Figure 3.

The average of the PIABS taken over four studies for four cultivars (Arkot 9704, VH260, DP393, and DP 210 B2RF) at non stressed (30°C) and heat stress (40°C) treatments, at 6 hours after elevated temperatures. Treatment values not connected by the same letters are significantly different (P < 0.05).

3.3 Performance index: PITOTAL

The largest difference between the heat-stressed and the control plants was observed with VH260 plants. VH260 also had the largest PITOTAL value of all the cultivars at 30°C (Figure 4). Ranking the cultivars based on the difference in values, DP 393 showed the least difference in values, followed by Arkot 9704 and DP210.

Figure 4.

The average of the PITOTAL taken over four studies for four cultivars (Arkot 9704, VH260, DP393, and DP 210 B2RF) at non stressed (30°C) and heat stress (40°C) treatments, at 6 hours after elevated temperatures. Treatment values not connected by the same letters are significantly different (P < 0.05).


4. Discussion

High temperature is one of the most important environmental factors that affect plant growth and development [43]. Because of these rising temperatures, heat stress is becoming a more frequent occurrence posing serious risks to crops. Future cotton production is reported to be subjected to multiple abiotic stresses, including extreme and prolonged high temperatures [44]. In cotton, the sensitive stage for heat stress is the reproductive stage [9, 13, 22] resulting in fruit abscission, smaller bolls, and decreased yields [45].

Climate change has caused a shift in necessity toward the identification of plants tolerant to abiotic stresses. In this cotton study, heat stress decreases the Fv/Fm values in all four cultivars to below the 0.75 boundary level for fully functional PSII system. In similar studies, [46] found decreased Fv/Fm values in cotton under drought stress as did [47] in cotton under heat stress.

The decreases in performance indexes that were found in this cotton study was in accordance to results in a study by [48] where heat stress decreased the performance indexes of heat-treated alfalfa cultivars. The decrease in performance indexes could indicate the lower photochemistry of PSII [30]. Bange et al. [49] recommended that in regions where there is a significant risk of heat stress, cultivars that demonstrate resilience to these stresses should be considered and irrigation management adapted to help mitigate the negative effects of heat stress as crop’s capacity to moderate tissue temperature though transpirational cooling is dependent upon adequate moisture supply. Higher than optimum temperatures have long been known to adversely affect several physiological and metabolic processes with detrimental effects on plant growth and yield. To that end, extensive efforts have been undertaken and heat-tolerant cultivars have been introduced [50].

In a study done by [51] van der Westhuizen (2017), where the author evaluated different screening methods to detect heat stress in Growth Chamber Studies, it was found that decreases in chlorophyll a fluorescence were obtained when genotypes were subjected to heat stress. This is in agreement with research in cotton by [19, 52, 53] who recorded genotypic differences in Fv/Fm in response to heat stress. Bibi et al. [19] found that an increase in temperature from 30.0°C to 33.0°C did not affect Fv/Fm significantly, however, at 36°C and above, Fv/Fm decreased significantly. This is in agreement with research in cotton by [52, 53] who recorded genotypic differences in Fv/Fm in response to heat stress. Wu (2013) [50] found that based on selection by Fv/Fm measurements, it was clear that wild cotton accessions were more tolerant to heat stress than a set of random accessions and check genotypes in a growth chamber.


5. Conclusion

In this study, the impact of elevated temperature on photosynthesis was significant in all four cultivars as reflected in the decrease in the maximum quantum yield of PSII (Fv/Fm) as well as decreased performance indexes (PIABS and PITOTAL). In cultivar DP393 the lowest drop in values for Fv/Fm, PIABS and PITOTAL, showed the genetic capacity of this cultivar to cope with heat stress. Considering all results, the cultivars VH260, DP210, and to a lesser extent Arkot 9704 were adversely affected by heat stress and therefore heat sensitive. It is recommended that the cultivar DP393 can be used as the basis in further cotton breeding programs as a source of tolerance for high-temperature stress.



The authors want to thank the University of North West (Potchefstroom), the National Research Foundation, University of Arkansas, CottonSA and the Agricultural Research Council – Institute for Industrial Crops for funding.


  1. 1. Wang H, Siddiqui MQ , Memon H. Cotton science and processing technology. Physical Structure, Properties and Quality of Cotton. 2020;5:79-98. Publisher: Springer Singapore
  2. 2. Gupta SK. Technological Innovations in Major World Oil Crops, Volume 1: Breeding. Heidelberg, Germany: Springer; 2011. p. 405
  3. 3. Vuletić MV, Mihaljević I, Tomaš V, Horvat D, Zdunić Z, Vuković D. Physiological response to short-term heat stress in the leaves of traditional and modern plum (Prunus domestica L.) cultivars. Horticulturae. 2022;8(72):1-14
  4. 4. Majeed S, Rana IA, Mubarik MS, Atif RM, Yang SH, Chung G, et al. Heat stress in cotton: A review on predicted and unpredicted growth-yield anomalies and mitigating breeding strategies. Agronomy. 2012;11(9):1825
  5. 5. Wahid A, Gelani S, Ashraf M, Foolad MR. Heat tolerance in plants: An overview. Environmental and Experimental Botany. 2007;61:199-223
  6. 6. Niinemets U. Mild versus severe stress and BVOCs: Thresholds, priming and consequences. Trends in Plant Science. 2010;15(3):145-153
  7. 7. Snider JL, Oosterhuis DM. How does timing, duration and severity of heat stress influence pollen-pistel interactions in angiosperms. Plant Signal and Behaviour. 2011;6(7):930-933
  8. 8. Zafar SA, Noor MA, Waqas MA, Wang X, Shaheen T, Raza M, et al. Temperature extremes in cotton production and mitigation strategies. In: Mehboob-Ur-Rahman, Afar YZ, editors. Past, Present and Future Trends in Cotton Breeding. Vol. 4. London: IntechOpen; 2018. pp. 65-91. DOI: 10.5772/intechopen.74648
  9. 9. Oosterhuis DM. Yield response to environmental extremes in cotton. In: Oosterhuis DM, editor. Proc. Cotton Research Meeting and Summaries of Research in Progress. Vol. 193. Fayetteville: Arkansas Agricultural Experiment Station, University of Arkansas Division of Agriculture; 1999. pp. 30-38
  10. 10. Pettigrew WT, Oosterhuis DM. Cotton, Climate Change and Agriculture: Effects and Adaptation. National Climate Assessment for Agriculture. Washington, DC: US Global Change Research Program; 2013
  11. 11. Hodges HF, Reddy KR, McKinion JM, Reddy VR. Temperature Effects on Cotton. In: Remy KH, editor. Mississippi Agricultural & Forestry Experiment. Department of Information Services, Division of Agriculture, Forestry and Veterinary Medicine, Mississippi State University Station, Mississippi State; 1993
  12. 12. Brown PW, Zeiher CA. A model to estimate cotton canopy temperature in the desert southwest. In: Dugger CP, Richter DA, editors. Proceeding of the Beltwide Cotton Conferences. Memphis, TN: National Cotton Council of America; 1998. p. 1734
  13. 13. Reddy KR, Hodges HF, Reddy VR. Temperature effects on cotton fruit retention. Agronomy Journal. 1992;84:26-30
  14. 14. Hatfield JL, Prueger JH. Temperature extremes: Effect on plant growth and development. Weather and Climate Extremes. 2015;10:4-10
  15. 15. Schlenker W, Roberts MJ. Nonlinear temperature effects indicate severe damages to U.S. crop yields under climate change. Proceedings of the National Academy of Sciences. 2009;106:15594-15598
  16. 16. Burke JJ. Variation among species in the temperature dependence of thereappearance of variable fluorescence following illumination. Plant Physiology. 1990;93:652-656
  17. 17. Crafts-Brandner SJ, Salvucci ME. Rubisco activase constrains the photosynthetic potential of leaves at high temperature and CO2. Proceedings of the National Academy of Sciences of the USA. 2000;2000(97):13430-13435
  18. 18. Wise RR, Olson AJ, Schrader SM, Sharkey TD. Electron transport is the functional limitation of photosynthesis in field grown Pima cotton plants at high temperature. Plant, Cell and Environment. 2004;27:717-724
  19. 19. Bibi A, Oosterhuis DM, Gonias ED. Photosynthesis, quantum yield of photosystem II and membrane leakage as affected by high temperatures in cotton genotypes. Journal of Cotton Science. 2008;12:150-159
  20. 20. Snider JL, Oosterhuis DM, Skulman BW, Kawakami E. Heat stress induced limitations to reproductive success in Gossypium hirsutum L. Physiologia. Plantarium. 2009;137:125-138
  21. 21. Law RD, Crafts-Brandner SJ. Inhibition and acclimation of photosynthesis to heat stress is closely correlated with activation of ribulose-1,5-bisphosphate carboxylase /oxygenase. Plant Physiology. 1999;120:173-182
  22. 22. Snider JL, Oosterhuis DM and Kawakami EM. Genotypic differences in thermotolerance are dependent upon pre-stress capacity for antioxidant protection of the photosynthetic apparatus in Gossypium hirsutum L. Plant Physiology. 2010;138:268-277
  23. 23. Sharkey TD, Schrader SM. High Temperature Stress. Physiology and Molecular Biology of Stress Tolerance in Plants. Berlin: Springer; 2006. pp. 101-129
  24. 24. Pilon C, Snider JL, Oosterhuis DM, Loka D. The effects of genotype and irrigation regime on PSII heat tolerance in cotton. Advances in Research. 2016;6(3):1-11
  25. 25. Mathur S, Agrawal D, Jajoo A. Photosynthesis: Limitations in response to high temperature stress. Journal of Photochemistry and Photobiology B. 2014;137:116-126
  26. 26. Wang Q-L, Chen J-H, He N-Y, Guo F-Q. Metabolic reprogramming in chloroplasts under heat stress in plants. International Journal of Molecular Sciences. 2018;19:849. DOI: 10.3390/ijms19030849
  27. 27. Misra AN, Mira M, Singh R. Chlorophyll fluorescence in plant biology. In: Misra AN, editor. Biophysics. London: IntechOpen; 2012. pp. 171-192
  28. 28. Strasser RJ, Tsimilli-Michael M, Srivastava A. Analysis of chlorophyll a fluorescence transient. In: Papageorgiou GC, Govindjee, editors. Chorophyll a Fluorescence - a Signature of Photosynthesis, Advances in Photosynthesis and Respiration. Vol 19. Rotterdam, The Netherlands: Kluwer Academic Publishers; 2004. pp. 321-362
  29. 29. Kitajima M, Bultler WL. Quenching of chlorophyll fluorescence and primary photochemistry in chloroplasts by dibromothymoquinone. Biochemistry Et Biophysics Acta. 1975;376:105-115
  30. 30. Kalaji HM, Jajoo A, Oukarroum A, Brestic M, Zivcak M, Samborska I, et al. Chlorophyll a fluorescence as a tool to monitor physiological status of plants under abiotic stress conditions. Acta Physiologiae Plantarum. 2016;38:102
  31. 31. Strasser RJ, Tsimilli-Michael M, Srivastava A. Analysis of the chlorophyll a fluorescence transient. In: Papageorgiou GC, Govindjee, editors. Advances in Photosynthesis and Respiration. Chlorophyll a Fluorescence: A Signature of Photosynthesis. Dordrecht: Kluwer Acad. Publ; 2005. pp. 321-362
  32. 32. Butler W, Kitajima M. Fluorescence quenching in photosystem II of chloroplasts. Biochimica et Biophysica Acta. 1975;376:116-125
  33. 33. Baker NR. Chlorophyll fluorescence: A probe of photosynthesis in vivo. Annual Review of Plant Biology. 2008;59:89-113
  34. 34. Živčák M, Brestič M, Olšovská K, Slamka P. Performance index as a sensitive indicator of water stress in Triticum aestivum L. Plant, Soil and Environment. 2008;54:133-139
  35. 35. Strasser RJ, Srivastava A, Tsimilli-Michael M. Screening the vitality and photosynthetic activity of plants by fluorescence transient. In: Behl RK, Punia MS, Lather BPS, editors. Crop Improvement for Food Security. Hisar: SSARM; 1999. pp. 72-115
  36. 36. Appenroth KJ, Stöckel J, Srivastava A, Strasser R. Multiple effects of chromate on the photosynthetic apparatus of Spirodela polyrhiza as probed by OJIP chlorophyll a fluorescence measurements. Environmental Pollution. 2001;115:49-64
  37. 37. Stirbet A, Lazár D, Kromdijk J, Govindjee G. Chlorophyll a fluorescence induction: Can just a one-second measurement be used to quantify abiotic stressresponses? Photosynthetica. 2018;56:86-104. DOI: 10.1007/s11099-018-0770-3
  38. 38. Van Heerden PDR, Tsimilli-Michael M, Krüger GHJ, Strasser RJ. Dark chilling effects on soybean genotypes during vegetative development: Parallel studies of CO2 assimilation, chlorophyll a fluorescence kinetics O-J-I-P and nitrogen fixation. Physiologia Plantarum. 2003;117:476
  39. 39. Tsimilli-Michael M, Strasser RJ. In vivo assessment of stress impact on plant's vitality: Applications in detecting and evaluating the beneficial role of mycorrhization on host plants. In: Varma A, editor. Mycorrhiza 3. Berlin: Springer; 2008. pp. 679-703
  40. 40. Hao X, Zhou S, Han L, Yu Zhai Y. Differences in PItotal of Quercus liaotungensis seedlings between provenance. Scientific Reports. 2021;11:23439. DOI: 10.1038/s41598-021-02941
  41. 41. Maxwell K, Johnson GN. Chlorophyll fluorescence -a practical guide. Journal of Experimental Botany. 2000;51(345):659-668
  42. 42. Havaux M. Stress tolerance of photosystem II in vivo - antagonistic effects of water, heat and photoinhibition stresses. Plant Physiology. 2004;100:424-432
  43. 43. Mohamed HI, Abdel-hamid AME. Molecular and biochemical studies for heat tolerance on four cotton genotypes. Romanian Biotechnological Letters. 2013;2013(18):7223-7231
  44. 44. Dabbert TA, Gore MA. Challenges and perspectives on improving heat and drought stress resilience in cotton. Journal of Cotton Science. 2014;18:393-409
  45. 45. Reddy KR, Davidonis GH, Johnson AS, Bryan T, Vinyard BT. Temperature regime and carbondioxide enrichment alter cotton boll development and fiber properties. Agronomy Journal. 1999;1999(91):851-858
  46. 46. Li D, Li C, Sun H, Liu L, Zhang Y. Photosynthetic and chlorophyll fluorescence regulation of upland cotton (Gossypium hirsutum L.) under drought conditions. Plant Omics Journal. 2012;5:432-437
  47. 47. Wu T, Weaver DB, Locy RD, McElroy S, van Santen E. Identification of vegetative heat-tolerant upland cotton (Gossypium hirsutum L.) germplasm utilizing chlorophyll fluorescence measurement during heat stress. Plant Breeding. 2014;133(2):250-255
  48. 48. Wassie M, Zhang W, Zhang Q , Ji K, Chen L. Effect of heat stress on growth and physiological traits of alfalfa (Medicago sativa L.) and a comprehensive evaluation for heat tolerance. Agronomy. 2019;9(10):597. DOI: 10.3390/agronomy9100597
  49. 49. Bange MP, Baker JT, Bauer PJ, Broughton KJ, Constable GA, Luo Q , et al. Climate change and cotton production in modern farming systems. ICAC review Articles on Cotton Production Research. 2016;6:1-61
  50. 50. Loka DA, Oosterhuis DM. Physiological and biochemical responses of two cotton (Gossypium hirsutum L.) cultivars differing in Thermotolerance to high night temperatures during Anthesis. Agriculture. 2020;10(9):407. DOI: 10.3390/agriculture10090407
  51. 51. van der Westhuizen MM. Evaluation of Screening Methods to Detect Heat Stress in Diverse Cotton Genotypes [graduate theses and dissertations]. University of Arkansas; 2017. Retrieved from:
  52. 52. Wu T. Identification of vegetative heat-tolerant upland cotton (Gossypium hirsutum L.) germplasm utilizing chlorophyll fluorescence measurement during heat stress. Plant Breeding. 2014;133:250-255. Blackwell Verlag GmbH. Doi: 10.1111/pbr.12139
  53. 53. Zhang J. Study of Thermotolerance Mechanism in Gossypium hirsutum L. through Identification of Heat Stress Genes. [Thesis]. Fayetteville: University of Arkansas; 2013

Written By

Jacques M. Berner, Mathilda Magdalena van der Westhuizen and Derrick Martin Oosterhuis

Submitted: 18 February 2022 Reviewed: 21 March 2022 Published: 07 September 2022