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Plant Ecophysiology 3 (2009) 129-133 Effect of leaf clipping on yield and quality traits of three corn cultivars S. Hamzi Alvanagha, A.M. Modarres-Sanavia*, M. Aghaalikhanib, F. Khazaeib, and H. Heidari- aDepartment of Agronomy, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran. bSeed and Plant Certification and Registration Institute, Karaj, Iran. Abstract
In order to study the relation between sink and source in corn plants, a field experiment was conducted as a factorial experiment in a Randomized Complete Block Design with three replications. A total of 3 cultivars (301, 604 and 700) and four leaf clippings (without leaf clipping, ear leaf clipping, above ear leaf clipping, and below ear leaf clipping) were used during 2007 crop season. Results showed that oil, grain yield, globulin, glutamine, and carbohydrates were different among cultivars and treatment compositions. Leaf clipping did not affect oil, globulin and carbohydrates but yield and other quality traits were influenced by leaf clipping. Grain yield reduction was observed in 700, 406 and 301 in ascending order. The highest grain yield was observed in all cultivars under control treatment. Ear leaf clipping and below ear leaf defoliation ranked second for yield production. The lowest yield was observed in above ear leaf clipping treatment. Overall, all leaf clipping treatments produced similar amounts of oil, globulin and carbohydrates. The highest glutamine was obtained in above ear leaf clipping that was similar with ear leaf clipping treatment. Control treatment had the lowest glutamine similar to ear leaf clipping and below ear leaf clipping treatments. Above ear leaf clipping strongly increased grain prolamine and albumin. The lowest prolamine was obtained from below ear leaf clipping and without leaf clipping treatments. but the minimum grain albumin was belonged to ear leaf clipping. Leaf clipping treatments were ranked in four different groups with aspect to grain albumin concentration whereas control and below leaf clipping treatments had no difference in grain prolamine. The highest oil, globulin, glutamine, prolamine and carbohydrate belonged to the cultivar 604. Globulin concentration in grain of 604 and 700 cultivars and prolamine in grain of 604 and 301 cultivars were similar. Cultivar 301 produced the lowest globulin and prolamine but its oil, glutamine and carbohydrates were similar to 700 and 301 cultivars. Cultivar 700 produced the highest albumins under above ear leaf clipping treatment. Keywords: protein; oil; corn; leaf clipping; carbohydrates. Introduction
hydrates stored in embryo and endosperm could be changed by environmental conditions and stresses. Different types of leaf clipping have var- source, animal feed, and a source of carbohy- ious influences on dry matter accumulation, oil drate, oil, protein and fiber. It is principally used and soluble carbohydrates percentage and grain as an energy source in animal feeds. Most corn soluble proteins. The effect of leaf clipping at grain is handled as a commodity, since many of V5- V13 on corns with high oil concentration is the industrial and animal feed requirements for about 50 to 100 percent. Leaf clipping will de- corn can be met by common varieties of field crease the amount of oil in corn cultivars with corn which are widely grown and produced. Corn high oil concentration rather than the other corn Grain proteins include globulin, glutenin, albu- cultivars. In an experiment it was noticed that the min, zein and prolamine. Prolamine is the main interaction between cultivar and leaf clipping in corn grain protein (WIPO, 2006). Oil and carbo- two hybrids was significant. Determination of oil decrease in corns with high oil content is more pronounced than the other corns with normal oil S. Hamzi Alvanagh et al. / Plant Ecophysiology 3 (2009) 129-133 content (Thomison, 2005). Tassel clipping two In another research, it was noticed that there was days after silking increased the grain yield 6.7 not any interaction between different rates of ni- percent more than the control cultivar due to in- trogen fertilizer and leaf clipping but the interac- creased grain weight. Leaf clipping of upper tion between genotype and leaf clipping for yield three leaves 2 and 16 days after tasseling de- and grain protein rates was noticed. Hybrids creased grain yield 24 and 9 percent, respective- which produced more grain number were af- ly. When the leaf clipping occurs at the primary fected by leaf clipping treatment very scarcely stage of grain development, the grain yield de- and their protein decreased less than the other crease would arise due to increased grain number hybrids (Francis, 1999). Evaluation of source and (Wang, 1996). Complete leaf clipping at five-leaf sink limitation in two soybean cultivars (early stage in early maturing cultivars increased the mature and late mature) showed that shadow de- yield compared to late-maturing cultivars at the creased grain yield and grain carbohydrate rate same condition. The average of yield increment about 9 to 32 percent. Also, starch content in late- for three years was about 48 percent. By leaf maturing cultivar was either stable or declined at clipping at five-leaf stage in early maturing culti- grain filling duration but increased in early- var, the yield was increased 26 percent more than maturing plants at the first stage of grain filling late-maturing cultivar. So, the response of early- duration. The grains of plants which had limita- maturing and late-maturing cultivars was differ- tion on their sinks were not able to use possible ent, specifically at five-leaf stage (WIPO, 2006). carbohydrates (Burton, 2004). The effect of leaf In an experiment, the effects of leaf clipping on clipping in rangeland plants at different stages (1, chemical constituents of four pearl millet culti- 2 and 4-leaf stages) cleared that early leaf defoli- vars were studied. Six-twelve weeks after stem ation decreased soluble carbohydrates and dry length reached 20- 40 centimeters, leaf clipping matter accumulation of tillers, roots and leaves. was done. Genotypes included S360, S4 and S41. Also, next carbohydrates recycling duration was In the first year without leaf clipping, the yield decreased. Leaf defoliation at one-leaf stage lim- and soluble protein rates were the same but in the its the plant re-growth. But leaf defoliation at 2- second year by using leaf clipping, soluble pro- leaf stage provide enough time for carbohydrates tein rates of S41cultivar was greater than S4 fol- recycling and leaf defoliation at 4-leaf stage pro- lowed by S360 (Bisoondat, 2002). Leaf clipping duce the most soluble carbohydrates and dry mat- at early season significantly decreased the stem ter accumulation of tillers, roots and leaves (Bur- length and leaf area but it did not have any effect on leaf emergence. Also, leaf clipping at early season decreased soluble grain carbohydrate in Materials and Methods
order to devote the carbohydrates for vegetative growth and reduce sucrose sources (Prioul and A field experiment as a factorial experiment Dugue, 1992). It was noticed that when the defol- in a randomized complete block design with three iation is severe and its time is closer to silking replications was conducted in research field of stage, forage yield and soluble sugars would be Tarbiat Modarres university (Latitude: 35° 43' N., decreased greatly (Burton, 2004). It was reported Longitude: 51° 8’ E., and 1215 meters above sea that 33 percent of corn defoliation in irrigated level) in summer 2007, to study the relations be- condition at 28 and 35 days after germination tween sink and source in corn plants. A total of 3 decreased the soluble protein rates more than cultivars (301, 604 and 700) and four leaf clip- stress condition with 33 and 67 percent defolia- pings (without leaf clipping, ear leaf clipping, tion (Lauer, 2004). The effect of leaf defoliation above ear leaf clipping, and below ear leaf clip- on canopy photosynthesis and changing the sink and source carbohydrates showed that soluble The soil of the experimental site was sandy sugars in plants with leaf clipped (control, above loam with pH value of 7.4, organic matter of ear leaf clipping, below ear leaf clipping and full 1.48%, clay of 15.1%, sand of 61%, and silt of leaf clipping at flowering stage) was different. It 23.9%. The different seeds were planted at the was observed that full leaf clipping treatment same time and treatments were applied one week made the most decrement of canopy photosyn- after pollination. Grains final harvesting was thesis and changing the sink and source carbohy- done when black layer formed at basal part of drates and the percentage of soluble sugar in dif- grains. In final grain harvesting, 10 plants re- ferent parts of plant such as grains (Egile, 2000). moved and their ears were separated and putted S. Hamzi Alvanagh et al. / Plant Ecophysiology 3 (2009) 129-133 Table 1. Variance analysis and mean comparisons of yield and quality traits of different corn cultivars under leaf clipping treatments ns, * and **: not significant, significant at 5 and 1 % levels of probability, respectively. into an oven at 75°C. Grains were weighed and a samples that their albumin, globulin and prola- sub sample of each cultivar grain was put in hy- mine had been separated (for glutenin separation) grometer and their moisture contents were meas- and the other steps were continued as before. Results and Discussion
used for measuring soluble sugar. Also, Succule method was used for assessing the seed oil con- Results revealed that cultivar and leaf clipping tent. Furthermore, Bradford method was used for treatments had significant effects on oil, grain extraction and quantitative determination of seed yield, globulin, glutenin, prolamine, albumin and storage proteins (Bradford, 1976). At first, 200 soluble carbohydrates. Leaf clipping treatments mg oil extracted sample was weighed and poured did not have significant effect on oil, globulin into 1.5 ml micro tube cuvettes and 1 ml of two and carbohydrates but they had significant effect times diluted water was added (for albumin sepa- on yield and other seed quality traits. Grain yield ration) and shaken for about 20 minutes. Then, reduction was observed in 700, 406 and 301 in an the upper part of liquid was separated at 10,000 x ascending order. The highest grain yield was ob- g for 6 minutes and stored at -24°C. In addition, 1 served in all cultivars under control treatment. M NaCl was added to samples that their albumin Ear leaf clipping and below ear leaf defoliation had been separated (for globulin separation) and ranked second for yield production. The lowest the other steps were continued as before.1ml pure yield was observed in above ear leaf clipping ethanol was added to samples which their albu- treatment (Table 1). Below ear leaf clipping and min and globulin had been separated (for prola- control treatments in early-maturing cultivars mine separation). At the end, 1 ml of 0.2 M produced similar grain yield but in medium and phosphate buffer (pH = 8.0) was added to the late-maturing cultivars, the yield of control S. Hamzi Alvanagh et al. / Plant Ecophysiology 3 (2009) 129-133 treatments was more than the other treatments. reas the lowest grain yield was produced from Grain yield reduction was according to the defo- cultivar 301 with the above ear leaf clipping liated leaf number and this reduction was related treatment (Table 1). In an experiment, by classi- to the grain number decrease (Allison, 1995). fying corn leaves in three categories (above ear Also, 1000-grain weight did not have any influ- leaves, ear leaf and below ear leaves) it was ob- ence on grain yield reduction. All types of leaf served that different leaves did not have similar clipping treatments at 30 days after 50% silking effects on yield (Yao, 1999). It seems that the can result in severe yield reduction. Main reason below ear leaves as the above ear leaves have of this issue is related to grain number reduction significant effects on seed filling. Because of (Wilhelm and Etora, 1995). Overall, all leaf clip- that, below ear leaf defoliation in cultivar 700 ping treatments produced similar amounts of oil, reduced the yield but by clipping the ear leaf, globulin and carbohydrates. The highest gluta- yield was increased. Increment of grain yield in mine was obtained from the above ear leaf clip- late-maturing, defoliated cultivars was due to ping that was similar to ear leaf clipping treat- better light interception through canopy (Reed, ment. Control treatment had the lowest glutamine 1988). The highest grain yield reduction was rec- being similar to the ear leaf clipping and below orded when the above ear leaves had been defo- ear leaf clipping treatments. Above ear leaf clip- liated (Yao, 1999). The highest oil percentage ping strongly increased grain prolamine and al- was related to cultivar 604 with below and ear bumin. The lowest prolamine was obtained from leaf defoliations and control treatment of this cul- the below ear leaf clipping and without leaf clip- tivar was placed in next order. Cultivar 700 with ping treatments but the minimum grain albumin below ear leaf defoliation produced the lowest oil belonged to the ear leaf clipping. Leaf clipping percent but more oil percent was achieved from treatments were ranked in four different groups the ear leaf clipping treatment of this cultivar with respect to grain albumin concentration whe- reas the control and below leaf clipping treat- Below ear leaf clipping in early maturing cul- ments did not have difference in grain prolamine tivar at 5-leaf stage showed that some characte- (Table 1). The effect of leaf defoliation on pro- ristics such as plant height, protein and oil per- tein concentration in two soybean cultivars (high centage were higher than control cultivar (Turner, and low protein concentration) showed that the 2006). Oil percentage from early and medium- above leaf defoliation caused reduction in grain maturing cultivars was more than lat-maturing protein concentration in two cultivars (Bruening, cultivars. The highest and lowest globulin rates 2001). The highest rate of oil, globulin, gluta- achieved from cultivar 700 with the above ear mine, prolamine and carbohydrate belonged to leaf clipping and cultivar 301 with the below ear SC604. Globulin concentration in 604 and 700 leaf clipping, respectively (Table 1). Also, there and prolamine in 604 and 301 cultivars were sim- was not any decrease in soluble proteins by the ilar. Cultivar 301 produced the lowest globulin above ear leaf defoliation. But 30 % ear leaf de- and prolamine but its oil, glutamine and carbohy- foliation decreased soluble proteins (Yang, drates were similar with cultivar 700 which were 2004). Globulin content of early-maturing culti- defoliated on the above ear leaf clipping (Table var was less than medium- and late-maturing 1). The relation between source and sink and ones. It seems that ear leaf defoliation has in- grain sucrose concentration and soluble protein creased globulin content or does not have any rates in soybean under leaf clipping treatment influence on globulin content. The highest and were investigated by Burton (2004). His results lowest glutenin concentrations achieved from revealed that leaf clipping reduced endosperm cultivars 604 and 301, respectively, both with the sucrose concentration about 80% and soluble above ear leaf clipping (Table 1). Applying 50% protein rates and grain development in one of the shadow treatment at vegetative phase in late- cultivars increased but it was decreased in the maturing cultivars did not have influence on so- other cultivar. But in the current experiment, luble proteins (Lauer, 2004). But at this experi- there were not significant differences between ment, soluble proteins were affected by shadow leaf clipping treatments with respect to carbohy- treatment. Cultivar 604 with the above ear leaf drate concentrations and the reason of that can be clipping produced the highest prolamine ratio due to soybean and corn plants differences (Bur- whereas cultivar 700 with the control treatment ton, 2004). The highest grain yield achieved from produced the lowest prolamine ratio (Table 1). It cultivar 700 without leaf clipping treatment whe- was recognized that below ear leaf defoliation in S. Hamzi Alvanagh et al. / Plant Ecophysiology 3 (2009) 129-133 late-maturing cultivars caused reduction in some References
soluble carbohydrates (Burton, 2004). Below ear leaf defoliation in early, medium- and late- Allison, J.C. 1995. The production and defoliation of dry maturing cultivars made increment or unchanged matter in maize after flowering. Ann. Bot. 30: 365- globulin, glutenin, prolamine and albumin ratio. Bisoondat, M. 2002. Defoliation effects on persistence The main reason of this issue was due to grain and productivity of four millet. Agronomy Journal. yield reduction because of the above ear leaf clipping. The highest and lowest carbohydrates Bradford, M. 1976. A rapid and sensitive method for achieved from 604 and 301 cultivars with the quantification of microgram quantities of protein above ear leaf clipping, respectively (Table 1). utilizing the principle of protein dye-binding. Above ear leaf defoliation at pollination time in Bruening, W.P. 2001. Source-sink relations ships, seed late-maturing cultivars caused reduction in seed sucrose levels and soluble protein seed growth rates storage carbohydrate but not as severe as early- in soybean. Annals of Botany. 88: 235- 242. maturing cultivars (Early, 1966). Grain filling Burton, W.J. 2004. Effects of defoliation on seed protein ratio depends on transition of fixed carbon from concentration in normal and high protein lines of leaves. Ear leaf defoliation retransmitted accumu- lated matter from stem to grain (Egile, 2000). Early, E.B. 1966. Effect of defoliation on maize Above and below ear leaf clippings did not production under field condition. Crop science. 7: 151-15. change grain soluble carbohydrates compared to Egile, D.B. 2000. Variation in leaf starch and sink control treatment in three cultivars. So, carbohy- limitations during seed filling in soybean. Crop drate content does not have any influence on making decision about leaf defoliation ratio. Leaf Francis, C.A. 1999. Differential response to defoliation clipping at stress condition would lead to favora- of grain sorghum yield components and yield related ble results compared to normal condition. This is Irigoyen, J.J., and D. Emerich. 1992. Water stress likely due to the fact that in stress condition, tran- induced changes in concentrations of proline. sition of accumulated matter to grains is higher and more sources available makes limitation to Lauer, J.G. 2004. Impact of defoliation on corn forage physiological sinks. So, applying below ear leaf yield. Agronomy Journal. 96: 1458- 1463. defoliation at stress condition can prohibit yield Prioul, J.L., and N.S. Dugue. 1992. Kernel growth rate quantity and quality reduction compared to nor- and duration in maize as effected by plant density and genotype. Crop Science. 19:385-388. mal condition (Lauer, 2004). Hence, enough Reed, A.J. 1988. Shading affects on dry matter and yields are main achievements for farmers. On the nitrogen partitioning, kernel number, and yield of other hand, leaf clipping can decrease corn yields. So, using grain corn instead of forage Thomison, P.R. 2005. Early season defoliation effects on must be prohibited. Below ear leaf clipping had top cross high-oil corn production. Agronomy the lowest influence on three cultivars with re- spect to qualitative and quantitative yield because Turner, L.A. 2006. Effect of defoliation on water soluble carbohydrate and nitrogen energy reserves, re-growth they can increase quality of grain or do not of leaves and roots, and tiller number of pasture change it compared with control. Above ear leaf plants. Agriculture Science. 57: 243-249. defoliation caused more decrement of yield com- Wang, O.Q. 1996. Effects of altered source sink ratio on pared to below ear leaf defoliation in medium- canopy photosynthetic rate and yield of maize. and early-maturing cultivars. Overall, grain quali- ty of the above ear leaf defoliation was better Wilhelm, W.W., and L. Etora. 1995. Yield quality and nitrogen use of inbred corn with varying numbers of than the other leaf clipping treatments but accord- leaves removed during detasselling. Crop Science. ing to issues mentioned, above ear leaf defolia- tion is not recommended. Also, above and below WIPO. 2006. Improved grain quality through altered ear leaf defoliation did not change grain soluble carbohydrate compared to control. Meanwhile, the above and below ear leaf defoliations can be Yang, Z. 2004. Experimental assessment of the impact of done. So, carbohydrates concentration did not defoliation on growth and seed production of water stressed maize. Agriculture Science. 2: 189- 199. have any influence on our decision for leaf defol- Yao, N.R. 1999. Effect of timing of defoliation on growth, yield components and seed components in maize. Agriculture Science. 27: 137- 144.

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