EFFECT OF PLANT GROWTH REGULATORS ON MANIPULATION OF SOURCE-SINK RELATIONSHIPS IN PIGEONPEA (Cajanus cajan L.) Dissertation Submitted to the Punjab Agricultural University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in BOTANY (Minor Subject: Biochemistry) By Kanchan Pahwa (L-2009-BS-44-D) Department of Botany College of Basic Sciences and Humanities ©PUNJAB AGRICULTURAL UNIVERSITY LUDHIANA-141004 2013 CERTIFICATE I This is to certify that the dissertation entitled, “EFFECT OF PLANT GROWTH REGULATORS ON MANIPULATION OF SOURCE-SINK RELATIONSHIPS IN PIGEONPEA (Cajanus cajan L.)” submitted for the degree of Ph.D., in the subject of Botany (Minor subject: Biochemistry) of the Punjab Agricultural University, Ludhiana, is a bonafide research work carried out by Ms. Kanchan Pahwa (L-2009-BS-44-D) under my supervision and that no part of this dissertation has been submitted for any other degree. The assistance and help received during the course of investigation have been fully acknowledged. Major Advisor (Dr. (Mrs.) Navita Ghai) Botanist Department of Botany College of Agriculture Punjab Agricultural University Ludhiana - 141004 (India) CERTIFICATE – II This is to certify that the dissertation entitled, “EFFECT OF PLANT GROWTH REGULATORS ON MANIPULATION OF SOURCE-SINK RELATIONSHIPS IN PIGEONPEA (Cajanus cajan L.)” submitted by Ms. Kanchan Pahwa (L-2009-BS-44-D) to the Punjab Agricultural University, Ludhiana, in partial fulfillment of the requirements for the degree of Ph.D., in the subject of Botany (Minor Subject: Biochemistry) has been approved by the Student’s Advisory Committee after an oral examination on the same. _______________________ _______________________ Major Advisor External Examiner (Dr. (Mrs.) Navita Ghai) (Dr. N.S. Atri) Professor and Head Department of Botany Punjabi University, Patiala ____________________ Head of the Department (Dr.(Mrs.) S.K. Thind) ________________________ Dean, Post-Graduate Studies (Dr. Gursharan Singh) ACKNOWLEDGEMENTS Glory to Waheguru, most gracious with whose grace and blessings, I have been able to conquer another task of my life. I consider myself fortunate and greatly privileged to work under supervision and guidance of Dr (Mrs) Navita Ghai, Botanist, Department of Botany, for her affectionate and unending encouragement, parental attitude and creative suggestions throughout the tenure of my degree. The critical advices given have helped me to overcome many tough moments of life. May God fulfill all her aspirations and desires! I express my sincere thanks to Dr (Mrs) S.K.Thind, Professor-cum-Head, Department of Botany, for her help, cooperation and guidance whenever required. I am extremely grateful to all the members of my advisory committee, Dr (Mrs) Seema Bedi, Professor, Department of Botany, Dr (Mrs) Satvir Kaur Grewal, Assistant Biochemist, Department of Biochemistry, Dr Sarvjeet Singh, Sr. Plant Breeder (Pulses), Department of Plant Breeding and Genetics and Dr (Mrs) Jagmeet Kaur, Senior Botanist, Department of Plant Breeding and Genetics. I owe my sincere thanks to Dr (Mrs) G K Sangha, Department of Zoology, Dr (Mrs) M K Sangha, Department of Biochemistry, Dr Inderjit Singh, Department of Plant Breeding and Genetics (Pulses Section), Dr Kushal Singh, Department of Floriculture and Land scaping and Dr (Mrs) Neelima Arora, Dr (Mrs) Usha Parmar & Dr (Mrs) Nirmaljit Kaur, Department of Botany. I also gratefully acknowledge the ever- willing cooperation of Dr Javed, Statistician, Department of Math, Stats & Physics. I am extremely thankful to Dr MSA Fakir for providing me valuable research articles. It is rightly said that "Every effort is motivated by ambitious and all ambitions have an inspiration behind." I owe this pride place to my parents. They served as source of motivation to work hard without weary and remain jovial even in odd situations. I owe immensely to my Dad, Mom, Sisters, Jijus and my lovely brother Gagandeep for their tender care, love, heartfelt blessings and selfless sacrifices that brought me to this level. Special love thoughts for blooming buds of the family Shalok, Eric and Davina whose innocent stammering voices made me laugh in tough times. I offer my heartful appreciation to my ever helping seniors Madhu, Ghonu, Aman, Tilak Raj, Parminder, Sonika , Jasdeep, Minakshi , Nisha , Shivali and Neha for their ever willing cooperation, moral support and rendering valuable assistance whenever and wherever need arose. I shall remain indebted at each and every step of my life for the replenishing support and cheerful company of my prudent friends Pardeep, Navkiran, Sony, Mandeep, Harpreet, Jasleen, Megha, Diksha, Dharminder, Madhuri and my sweet juniors Manpreet, Rupinder, Monia, Sukhpreet, Ruby, Jaspreet and Harjot. I am also thankful to the supporting field and laboratory staff for their untiring help during my research work. (Kanchan Pahwa) Title of the dissertation : Effect of plant growth regulators on manipulation of source-sink relationships in pigeonpea (Cajanus cajan L.) Name of the Student : Kanchan Pahwa and Admission No. (L-2009-BS-44-D) Major subject : Botany Minor subject : Biochemistry Name and Designation : Dr. Navita Ghai of Major Advisor Botanist Degree to be Awarded : Ph.D. Year of award of degree : 2013 Total pages in dissertation : 153 + VITA Name of the University : Punjab Agricultural University, Ludhiana-141004 ABSTRACT Field experiments were conducted at Punjab Agricultural University, Ludhiana during kharif season in the years 2010-11 and 2011-12 respectively with an objective to evaluate various groups of genotypes (early, mid, late and check) on the basis of pattern of growth, partitioning of dry matter, flower retention, growth efficiency and yield and to study the effect of foliar application of ethrel (100 and 200 μg ml-1) and cobalt chloride (10 and 15 μg ml-1) applied at vegetative and flowering stages on seed yield. Various morpho-physiological, biochemical and yield characteristics were analyzed at different developmental stages. Study conducted with early, mid, late and check genotypes of pigeonpea revealed marked differences in partitioning of assimilates to vegetative and reproductive parts at different stages of growth cycle. The higher CGR, RGR, leaf area, LAI, photosynthesis, stomatal conductance, pod set percentage in mid-duration group resulted in high yield. Further, reproductive efficiency of four mid-duration genotypes (AL 1578, AL 1593, AL 1702 and AL 201) was chemically manipulated by foliar application of ethrel and cobalt chloride. The parameters determining reproductive efficiency and yield were significantly improved due to reduction in flower abscission. Ethrel (100 and 200 μg ml-1) sprayed at vegetative stage and CoCl 2 (10 μg ml-1) sprayed at flowering stage efficiently improved seed yield and other biochemical traits through improved flower retention, pod formation , seed setting percentage and seed weight. Genotype AL 1578 exhibited high yield in all treatments including control as compared to all the genotypes. The leaves of treated plants exhibited higher level of chlorophyll, which provided better conditions for higher production of photosynthates to be utilized for grain yield due to larger sink resulting from increased branching and number of pods. The treatments also affected the content of various biochemical constituents (total soluble sugars, total soluble proteins, total starch content, total free amino acids, chlorophyll content as well as the activity of various enzymes viz., nitrate reductase (NR), invertase and PEP carboxylase). Correlation analysis showed significant positive relationships between plant height, crop growth rate, leaf area, number of pods/plant, pod set percentage, seed weight/plant, 100-seed weight and harvest index. Further, path analysis revealed leaf area, specific leaf weight and number of pods/plant had significant positive direct influence on yield. Path analysis of various biochemical traits with seed yield revealed that activities of nitrate reductase, total soluble proteins and total starch content in leaves and invertase activity, total starch in seeds showed positive direct effect on seed yield. These traits should be used as target traits to improve seed yield. Protein profiling in mature seeds revealed much denser bands in treated plants as compare to control and also number of bands were higher in treated plants. A study of pedicel anatomy revealed an increase in area of conducting tissues through PGRs application. This increase could be responsible for enhanced translocation of assimilates to flowers, thereby helping in their retention. Keywords: Pigeonpea, partitioning, abscission, nitrate reductase, yield, protein profiling, pedicel anatomy ___________________________ ___________________ Signature of the major advisor Signature of the student Koj gRMQ dw ivSw : Arhr iv`c plWt groQ grY Ulytrz dw sors-isMk (Source Sink) sbMDW au~qy Asr ividAwrQI dw nwm Aqy dwKlw nM. : kMcn pwhvw (AYl-2009-bI.AYs.-44-fI) mu`K ivSw : bnspqI ivigAwn au~p ivSw : rswiexk ivigAwn mu`K slwhkwr dw nwm Aqy Ahudw : fw. nvIqw GeI pOd ivigAwnI imlx vwlI ifgrI : pI.AY~c fI. ifgrI id`qy jwx dw swl : 2013 ku`l pMny : 153 + vItw XUnIvristI dw nwm : pMjwb KyqIbwVI XUnIvristI, luiDAwxw-141 004 pMjwb, Bwrq incoV swl 2010-11 Aqy 2011-12 iv`c Arhr dy iqMn smUhW (CyqI, ivclI Aqy dyr nwl p`kx vwlIAW nslW) dw ivkws, Pu`l Dwrn SkqI, ivkws inpuMnqw, su`ky pdwrQW dIAW vMfW Aqy au~pj dy ADwr qy mulWkx kIqw igAw[ iehnW iv`coN cxo vIAW PslW aupr bnsqpqk (Vegetative) Aqy Pu`l pYx (Flowering) dy pVwA qy eIQrl (100 Aqy 200 g ml-1) Aqy kobwlt klorweIf (10 Aqy 15 g ml-1) dw iCVkwA bIj JwV dy vwDy dy audyS nwl kIqw igAw[ keI qrHW dI AwikqR k, jYivk rswiexk Aqy JwV l`Cx dw ivSlySx v`KrIAW ivkws siQqIAW qy kIqw igAw [ cwr ivclIAW p`kx vwlIAW vDIAw nslW dI pRjnn SkqI nUM eIArql Aqy kobwlt klorwief dy iCVkwA nwl suDwirAw igAw [ CyqI, iv`clI Aqy dyr nwl p`kx vwlIAW nslW ny vYjItyitv Aqy rIprofkitv ih`isAW iv`c su`ky pdwrQW dI vMf iv`c vyKx Xog iBMnqw drsweI [ ijAwdw sI jI Awr, Awr jI Awr, p`qw Kyqr, pRkwS sMslySn, stomYtl knf`ktYNs, PlI l`gx dI pRqISq dy kwrn ivclI p`kx vwly iek`T ny vD` JwV id`qw [ cwr iv`clI p`kx vwlIAW nslW (ey AYl - 1578, ey AYl - 1593, ey AYl - 1702, ey AYl - 201) au~qy kobwlt klorweIf Aqy eIQrl dw iesqymwl kIqw igAw [ pRjnn SkqI Aqy JwV inrDwrq krn vwly mwxkW dw vwDw G`t Pu`l JVn kwrn hoieAw [ iCVkwA kIqy hoey bUitAW dy p`iqAW iv`c vD` kloroiPl dI mwqrw kwrn vD` pRkwS sMslySn dI ikirAw hoeI ijhVI ik v`D JwV pYdw krn iv`c m`ddgwr is`D hoey [ pRXogW ny keI rswieixk q`q (pUrn Gulx vwlI KMf, pUrn Gulx vwlI pRotIn, pUrn stwrc q`q, pUrn Ku`lHy AmIno Ayisf, kloroiPl q`q, nwl d y nwl keI ieMnjwiemz dI ikirAwvW ijvNy nweItRyt rYfUktYs, ienvrtyj Aqy pyp kwrboksIlyj qy vI Asr vyiKAw igAw AwpsI sbMD ivSlySx ny bUty dI lMbweI, Psl au~pj drjw, p`qw Kyqr, PlIAW dI igxqI, PlI Dwrn dI pRqISq, bIj pRqI bUtw Bwr, 100-bIj Bwr Aqy JwV iv`c swkwrwqmk sbMD drswey [pwQ kOPIiSeyNt mulWkx ny p`qw Kyqr, AYs.AYl.fblXU., Bwr Aqy JwV dw is`Dw sbMD drswieAw [ rswieixk pRXogW dy pwQ kOPIiSeyNt mulWkx ny bIj JwV dw nweItRyt rIfMktyj dI pRqIikirAw, pUrn Gulx vwlI pRotIn Aqy p`qy iv`c pUrn stwrc q`q Aqy ieMnvrtyj pRqIikirAw, bIjW iv`c pUrn stwrc q`q dy nwl is`Dw sbMD drswieAw [ ieh l`Cx bIj JwV dy vwDy leI tIcy dy qOr qy iesqymwl kIqy jwxy cwhIdy hn [ iCVkwA kIqy bUitAW dy p`ky bIjW iv`c pRotIn rUp ryKw ny ijAwdw Gxy Aqy ijAwdw sMiKAw iv`c pRotIn bYNf id`qy [ Pu`l dI fMfI dI GoK ny PGRs dy ivSlySx nwl kfM kitMg itSU dy Kyqr iv`c vwDw drswieAw [ ies vwDy kwrn Pu`lW nUM vD` AsImIlyts (assimilates) imldy hn jo ik iehnW dI Dwrn SkqI iv`c mdd krdy hn [ mu`K Sbd: Arhr dI dwl, su`ky pdwrQW dI vMf, nweItRyt rIfYktyz, JwV, pRotIn, Pu`l dI fMfI dI GoK [ __________________ ________________ mu`K slwhkwr dy hsqwKr iv`idAwrQI dy hsqwKr CONTENTS CHAPTER TOPIC PAGE NO. I. INTRODUCTION 1 – 4 II. REVIEW OF LITERATURE 5 – 28 III. MATERIAL AND METHODS 29 – 43 IV. RESULTS AND DISCUSSION 43 – 128 V. SUMMARY 129 – 131 REFERENCES 132 – 153 VITA CHAPTER I INTRODUCTION Pulses are basic ingredients in the diets of a vast majority of Indian population as they provide a perfect mix of high biological value when supplemented with cereals. Importance of pulses is relatively more in our country as its contribution in nutrient supply is far more (cid:87)(cid:75)(cid:68)(cid:81)(cid:3)(cid:87)(cid:75)(cid:68)(cid:87)(cid:3)(cid:76)(cid:81)(cid:3)(cid:36)(cid:86)(cid:76)(cid:68)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:90)(cid:82)(cid:85)(cid:79)(cid:71)(cid:3)(cid:68)(cid:86)(cid:3)(cid:68)(cid:3)(cid:90)(cid:75)(cid:82)(cid:79)(cid:72)(cid:17)(cid:3)(cid:40)(cid:68)(cid:70)(cid:75)(cid:3)(cid:83)(cid:79)(cid:68)(cid:81)(cid:87)(cid:3)(cid:82)(cid:73)(cid:3)(cid:68)(cid:3)(cid:83)(cid:88)(cid:79)(cid:86)(cid:72)(cid:3)(cid:70)(cid:85)(cid:82)(cid:83)(cid:3)(cid:76)(cid:86)(cid:3)(cid:89)(cid:76)(cid:85)(cid:87)(cid:88)(cid:68)(cid:79)(cid:79)(cid:92)(cid:3)(cid:68)(cid:3)(cid:81)(cid:68)(cid:87)(cid:88)(cid:85)(cid:72)(cid:182)(cid:86)(cid:3)(cid:80)(cid:76)(cid:81)(cid:76)(cid:3) nitrogen fertilizer factory, which enables it to meet its own requirement and also benefit the succeeding crops. In addition, pulses are excellent feed and fodder for livestock. Besides their dietary value and nitrogen fixing ability, pulses also play an important role in sustaining intensive agriculture by improving physical, chemical and biological properties of soil and are considered as excellent crops for diversification of cereal based cropping systems (Pothalkar 2007). Pigeonpea (Cajanus cajan L.) is an important multi-use shrub legume of the tropics and subtropics. The crop originated in India and moved to Africa about 4,000 years ago. Pigeonpea belongs to the family Fabaceae sub-family papilionaceae(cid:17)(cid:3)(cid:55)(cid:75)(cid:72)(cid:3)(cid:74)(cid:72)(cid:81)(cid:88)(cid:86)(cid:3)(cid:181)Cajanus(cid:182)(cid:3) (cid:69)(cid:72)(cid:79)(cid:82)(cid:81)(cid:74)(cid:86)(cid:3)(cid:87)(cid:82)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:86)(cid:88)(cid:69)(cid:3)(cid:87)(cid:85)(cid:76)(cid:69)(cid:72)(cid:3)(cid:181)(cid:38)(cid:68)(cid:77)(cid:68)(cid:81)(cid:68)(cid:72)(cid:182)(cid:3)(cid:88)(cid:81)(cid:71)(cid:72)(cid:85) (cid:87)(cid:85)(cid:76)(cid:69)(cid:72)(cid:3)(cid:181)(cid:51)(cid:75)(cid:68)(cid:86)(cid:72)(cid:82)(cid:79)(cid:72)(cid:68)(cid:72)(cid:182) (Aiyer 1947). Duthie and Fuller (1883) found two species Cajanus flavous and Cajanus bicolor under the genus Cajanus and (cid:90)(cid:72)(cid:85)(cid:72)(cid:3)(cid:70)(cid:68)(cid:79)(cid:79)(cid:72)(cid:71)(cid:3)(cid:68)(cid:86)(cid:3)(cid:181)(cid:87)(cid:88)(cid:85)(cid:182)(cid:3)(cid:68)(cid:81)(cid:71)(cid:3)(cid:181)(cid:68)(cid:85)(cid:75)(cid:68)(cid:85)(cid:182)(cid:15)(cid:3)(cid:85)(cid:72)(cid:86)(cid:83)(cid:72)(cid:70)(cid:87)(cid:76)(cid:89)(cid:72)(cid:79)(cid:92)(cid:17)(cid:3)(cid:55)(cid:75)(cid:72)(cid:3)(cid:68)(cid:87)(cid:87)(cid:72)(cid:80)(cid:83)(cid:87)(cid:3)(cid:82)(cid:73)(cid:3)(cid:70)(cid:79)(cid:68)(cid:86)(cid:86)(cid:76)(cid:73)(cid:76)(cid:70)(cid:68)(cid:87)(cid:76)(cid:82)(cid:81)(cid:3)(cid:82)(cid:73)(cid:3)(cid:83)(cid:76)(cid:74)(cid:72)(cid:82)(cid:81)(cid:83)(cid:72)(cid:68)(cid:3)(cid:90)(cid:68)(cid:86)(cid:3) also made by Mahta and Dave (1931). Pigeonpea (2n=22) is a often pollinating and upto 30% out crossing has also been reported in this crop. This is probably a function of environment and populations of pollinating insects (Sheldrake 1984). Pigeonpea (Cajanus cajan L.) is the fifth most important pulse crop in the world. Pigeonpea can be grown both as annual crop or perennial plants in homestead (Long and Lakela 1976, Liogier 1988). It is also known as red gram, congo pea, gungo pea, no eye pea, dhal, gandual and pois cajan. In India, it is second in area and 91% of world's pigeonpea is produced in India (Sodavadiya et al 2009). In year 2012, it was grown on 4.2 thousand hectares in Punjab and its total production was 3.9 thousand tonnes (Anonymous 2012). It also improves soil fertility through nitrogen fixation as well as from the leaf fall and recycling of the nutrients (Mapfumes 1993, Snapp et al 2002). It is an important pulse crop that performs well in poor soils and regions where moisture availability is unreliable or inadequate (Kimani 2001). It is the preferred pulse crop in dryland areas where it is intercropped or grown in mixed cropping systems with cereals or other short duration annuals (Joshi et al 2001). Pigeonpea has a wide range of products, including the dried seed, pods and immature seeds used as green vegetables, leaves and stems used for fodder and the dry stems as fuel. Pigeonpea is consumed either as decorticated splits or green seeds as vegetables. It has been found that vegetable pigeonpea are considered superior to dry splits in crude fiber, fat, protein digestibility as well as trace elements and minerals. Besides its nutritional value, pigeonpea also possesses various medicinal properties due to the presence of a number of polyphenols and flavonoids. It is an integral part of traditional folk medicine in India, China, and some other nations. Pigeonpea is known to prevent and cure human ailments like bronchitis, coughs, pneumonia, respiratory. Dhal has 25% protein with a good balance of all amino acids except methionine and cysteine (Zu et al 2006 and Fu et al 2007). The crop though accumulates maximum biomass, yet a proportionally low final yield is obtained due to higher partitioning of dry matter towards vegetative growth. Dry matter accumulation in the plant at progressive stages is a justified assessment of growth as a cumulative expression of different growth parameters. Further, it was observed that productivity of pigeon pea was not only dependent on accumulation of total amount of dry matter but its effective partitioning into economic sink seems to be key to increase the yield. Excessive vegetative growth, indeterminate growth habit, lack of moisture stress tolerance, poor source- sink relationship, poor harvest index and poor biomass production in summer sown crop are some of the major physiological factors responsible for low productivity of pigeonpea (Chudasama and Thaker 2007). Flower and fruit/pod drop is also one of the serious problems in this crop resulting in poor reproductive efficiency and consequently poor yield. Flower drop seems to be a wasteful strategy as it involves the loss of a considerable amount of energy and nutrients. However, the strategy appears primarily related to strong internal competition, in which a rapid purge of sink tissue may be useful (Doorn 2002). Flower abscission occurs both before and after fertilization. In some species, the mere lack of pollination, after a critical period, activates the abscission zones, and in other species the lack of fertilization, again after a critical period does so. Flower abscission in pigeonpea is known to be high (70-80%) without initiating pod setting percentage, but unlike other pulse crops weight of earlier and later pod set is same (Sheldrake and Narayanan 1979, Mallikarjuna and Saxena 2002, Sivaramakrishnan et al 2002). Therefore, the low yield in pigeonpea is due to poor pod set resulting from high flower and pod drops. Its potential for high yield and wide adaptability can contribute to bridging the pulse shortage, if higher partitioning of dry matter is accomplished towards the storage sinks (Sharma et al 2009). Previous studies indicate the possibility of using pigeonpea to produce pulp for paper industry (Akhtaruzzaman et al 1986, Choudhury et al 2008). Pigeonpea is more feasible than any other possible pulses due to its special characteristics. It has high ability to be used as mixed crop and can be grown in unconventional lands like homesteads, roadsides, public places and borders of the crop fields (Saxena et al 2005, Kalaimangal et al 2 2008). However, it has been observed that unfertilized flowers often abscise due to competition for carbohydrates (Aufhammer et al 1987, Aloni et al 1996). The movement of photoassimilates from the site of synthesis in leaf tissues (source) to the site of net accumulation in different tissues (sink) is under the potential control of numerous factors. Regulation of net flow of photoassimilates is an integrated process. The concentration gradient and ability of sink to assimilates between the source and sink is the primary determinant of the current rate of transport and pattern of partitioning. The intra and inter competition between flowers and immature pods associated with flower shedding, pod setting and pod filling is primarily determined by combination and balance of endogenous hormones. However, closer examination of various components involved in the overall process of partitioning indicates that endogenous plant hormones serve as modulators of many of the specific rate limiting constituents (Tekale et al 2009). The physiological efficiency of a plant can be improved by prolonging photosynthesis, reducing photorespiration, better partitioning of photo assimilates, improving mineral ions uptake and stimulating nitrogen metabolism. The growth and development of plant is a complex process and is under the control of three main factors viz., genetics, environment and endogenous growth substances. The genetic factors determine the potentiality of a plant for growth and the fullest expression of this potential in turn is under the control of various environmental factors. The enhanced productivity of crop through physiological approaches is chiefly achieved by coordinating plant processes to synthesize maximum dry matter production and partitioning major quantum of this increased dry matter into effective yield contributing factors. One of the reasons for new varieties giving increased yields is mainly because of the partitioning of larger proportion of their dry matter in economic parts of the plant. It may also be attributed to their better adaptation to the environment. These effects can also be achieved by certain growth regulators. Plant growth regulators are substances which when added in small amounts modify the growth of plant usually by stimulating or inhibiting part of the natural growth regulation. They are considered as new generation of agrochemicals after fertilizers, pesticides and herbicides (Kumar 2001). Plant growth regulators like promoters, inhibitors or retardants play a key role in internal control mechanism of plant growth by interacting with key metabolic processes such as nucleic acid and protein synthesis. Ethylene, a gaseous hormone has long been recognized as a growth inhibitor, but evidence is accumulating that ethylene can also promote growth (Pierik et al 2006). The stimulatory effect of ethylene is concentration and stage dependent. Ethylene is an inhibitor of cell division, cell expansion and transport of auxins which present expressive effects on the 3