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CROP ECOLOGY, MANAGEMENT & QUALITY

Boll Retention and Boll Size among Intrasympodial Fruiting Sites in Cotton

^a Northeast Res. Stn., Louisiana State Univ. Agric. Center, Winnsboro, LA 71295
^b Dep. Experimental Statistics, Louisiana State Univ. Agric. Center, Baton Rouge, LA 70803

* Corresponding author (dboquet{at}agctr.lsu.edu)

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Competition among cotton (Gossypium hirsutum L.) bolls for assimilates may affect boll retention and size, making it an important factor affecting productivity. A 4-yr field study was conducted on Commerce silt loam to evaluate relationships among fruiting sites (FS) on sympodial branches of cotton receiving preplant fertilizer N rates of 0, 28, 56, 84, 112, 140, or 168 kg ha^-1 or a preplant + sidedress application of 56 + 56 kg ha^-1 each year. For each FS on each sympodium, there were four possible competition levels based on boll retention or abscission at FS 1, 2, and 3. Competition levels were determined by natural retention or abscission of fruit. Boll retention and weight were influenced by competition level, year, sympodia, FS location on the sympodia and by N rate. Competition effects on boll retention were affected by N rate but not by sympodia. Conversely, competition effects on boll weight were not affected by N rate but were affected by sympodia. Boll weight at FS 1 increased when bolls were retained at FS 2 and 3. Retention of a boll at FS 1 increased boll retention at FS 2 but decreased boll weight at FS 2. In contrast, boll weight at FS 2 increased when bolls were retained at FS 3, or at FS 1 and 3. Fertilizer N increased boll weight at FS 2, except when a competing boll was present at FS 1. Apparent increased competition among FS on a sympodium had favorable effects on boll retention and on boll weight except for FS 2 when FS 1 retained a boll and FS 3 did not retain a boll.

Abbreviations: FS, fruiting sites

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
COTTON YIELD is determined by the number of FS that successfully retain mature bolls and by boll size. Boll retention is the more important factor in determining yield (Boquet et al., 1994; Reddy and Rao, 1970). Boll retention and weight are affected by a complex set of interacting factors that involve genetics, physiology, nutrition, field environment, and weather (Guinn, 1982). An additional factor affecting boll retention and boll weight may be intrasympodial interactions among bolls competing for water, nutrients, and photosynthates.

The evaluation of boll position and boll weight for their effects on yield and yield variation has been the subject of research for many decades. Most such research involved fruiting behavior of whole plants and not individual bolls or FS. In early work, Bartholomew and Janssen (1928) and Turner (1944) reported that N and K fertilizer increased cotton yield by increasing the number and size of bolls. Among plant nutrients, N had the largest effect on the number of bolls retained by cotton plants (Wadleigh, 1944). Constable (1991) reported that fruiting branches near, but not at, the bottom of the plant had the greatest fruit survival and largest bolls. Bolls were largest on fruiting branches at mainstem Nodes 7 to 13. Fruiting sites that had the highest percentage retention were also the sites that typically produced the largest bolls, but boll retention and size varied greatly with position on the plant (Boquet et al., 1993; Jenkins et al., 1990a). Fruit load already set, and not climatological factors, was determined to be the single most important factor affecting whole-plant boll retention during mid to late flowering (Ehlig and LeMert, 1973). In a glasshouse study, Gerik et al. (1989) reported that plant N status, location of the boll on the mainstem, and boll position on the sympodial fruiting branch determined its final weight. Nitrogen stress reduced boll number per plant to a greater extent than boll weight. Moore (1999) found that an increase in N rate increased the number of fruiting branches but did not affect boll retention at any fruiting positions. In contrast, Boquet et al. (1993) and Wadleigh (1944) found that increasing fertilizer N decreased boll retention and size in the lower canopy and increased boll set and size in the upper canopy of field-grown cotton.

In mid-South cotton, the bolls at 1st position fruiting sites (FS 1) on sympodial branches typically produce from 50 to 75% of the total yield, those at 2nd position fruiting sites (FS 2) produce 15 to 20% of the total yield, with the remaining 5 to 15% occurring at more distal positions and on monopodial branches (Boquet et al., 1994; Jenkins et al., 1990b). The higher yield percentage at FS 1 is related to higher percentage boll retention and larger bolls compared with FS 2 and 3. Jenkins et al. (1990a) attributed the reduced boll number and size at FS 2 and 3 on a given sympodium to preferential partitioning of photosnythate to the older bolls at FS1. The reasons for higher retention and larger bolls at FS 1 may be more complex, however, because average boll weight at FS 2 and 3 seems to be consistently less than FS 1 regardless of the presence or absence of bolls at FS 1 (Boquet et al., 1994; Constable, 1991). The competitive edge exhibited by FS 1 bolls may also be related to enhanced access to nutrients and water because of their proximity to the main stem, which results in larger and more efficient subtending leaves. Peoples and Matthews (1981) showed that the main stem leaf subtending a sympodium provided photosynthates primarily to FS 1 and then to FS 2 if the fruiting structure at FS 1 shed. Benedict and Kohel (1975) used ¹⁴C labeling to demonstrate that the primary source of photosynthates for a boll was its subtending leaf and the primary sink on a sympodium was FS 1. Removal of a boll from a sympodium redirected assimilates to the remaining bolls on the same sympodium (Peoples and Matthews, 1981), a process that helps to compensate for loss of bolls. Constable (1991) found, however, that, under natural field conditions, the loss of a boll did not appear to be fully compensated for by developing more or larger bolls on the same fruiting branch.

Kerby and Buxton (1981) studied the influence of boll retention at FS 1 on boll retention at FS 2 in normal and super-okra leaf cotton planted in 51-cm rows at low and high plant population densities. When the fruiting structure at FS 1 aborted as a square, retention at FS 2 averaged 17 to 33%. When FS 1 retained a boll, retention at FS 2 averaged 7 to 14%, demonstrating that the fate of FS 1 fruit had a large effect on boll retention at FS 2. Retention was determined 14 d after boll set and effects of boll retention on boll weight were not recorded. They concluded that, in narrow-row high-population culture, adjacent fruiting forms competed for assimilates and the potential for developing more than one boll per sympodial branch was low. Heitholt (1997) evaluated percentage boll set and boll size for sympodial branches from which young squares were artificially removed from selected positions and found that removing potential boll competition increased boll set and size of remaining bolls. Removing young fruit from FS 2 and 3 increased boll set and size at FS 1 and removing young fruit from FS 1 and 3 increased boll set at FS 2. Even with compensation that increased boll retention and size, however, both fruit removal treatments lowered yields compared with no fruit removal. He concluded that cotton may not be able to achieve its full yield potential if limited to one boll per main stem node. Pettigrew (1994) reported that fruit removal from a sympodium increased boll retention at the remaining FS, either FS 1 or 2. He found that fruit removal from sympodia early in the season increased the mass of bolls at FS 1 but not of bolls at FS 2. Fruit removal later in the season resulted in bolls at FS 1 and 2 with similar mass, which was greater than bolls in the control plots. Greater increase in boll mass in the upper canopy was attributed to a more favorable light environment for subtending leaves that provided sufficient assimilate to the developing bolls without the need for transport from other parts of the plant. Jones et al. (1996) reported that artificial removal of flowers during early anthesis was compensated for by an increase in the number of distal and more apical bolls.

Previous studies that evaluated competition among FS were conducted under artificial conditions (fruit removal), or without identifying reciprocal competition effects among all FS on boll retention and boll size. Apart from insect losses, there may be differences between plant responses to artificial fruit loss and responses to plant-dictated fruit abscission that is determined by the capacity of the plant to retain fruit. It is unlikely that artificial removal of a fruit that would not be aborted would have the same effect as normal fruit abscission in response to stress. Additionally, the effects of N availability on competition among FS 1, 2, and 3 that may influence retention and size of bolls on each sympodial branch have not been studied under field conditions. The objective of this study was to determine the intrasympodial interaction effects among bolls on percentage boll retention and boll size for each FS in cotton receiving different fertilizer N rates.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Field experiments were conducted to evaluate the effects of N fertility on boll retention and size among competing bolls at each FS on sympodial branches of rainfed cotton. The experiments were performed from 1987 through 1990 on Commerce silt loam (fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts) at the Northeast Research Station located 2 km west of St. Joseph, LA. The experiments were planted in late April each year with ‘Deltapine 41’ at a seeding rate of 120 000 seed ha^-1 to achieve a plant population density of 96 000 plants ha^-1. A range of N availability was established for the plants by applying preplant fertilizer N rates of 0, 28, 56, 84, 112, 140, or 168 kg^-1 or a preplant + sidedress application of 56 + 56 kg ha^-1 each year. The N fertilizer (NH₄NO₃) was applied broadcast and incorporated to a depth of 4 cm. The sidedress N was surface broadcast by hand just before bloom initiation. The N rate treatments were maintained on the same plots throughout the study. Fertilizer N rate effects on yield ha^-1 have been reported in an earlier publication (Boquet et al., 1994). Averaged across years, the seedcotton yields for N rates of 0, 28, 56, 84, 112, 140, and 168 kg ha^-1 were 2650, 3148, 3558, 3702, 3676, 3684, and 3453 kg ha^-1, respectively.

All potentially damaging insects were controlled with applications of insecticides. Aldicarb [2-methyl-2-(methylthio)propionaldehyde 0–(methylcarbamoyl)oxime]) was soil-applied at planting (1.2 kg ha^-1) for early-season control. Depending upon insect species and plant growth stage, appropriate insecticide treatments were foliar-applied at 5- to 7-d intervals beginning 20 d after planting and continuing until boll harvest began in early August.

Plots were 8 1-m wide rows 19 m in length. Each year at early bloom, 20 plants were randomly selected from the center four rows and marked with red tape for later identification and harvest. Seedcotton was hand-picked from mature (open) bolls from each plant at 3-d intervals beginning in early August and continuing until all bolls were harvested. As each boll was harvested, it was identified and labeled as to its location on a sympodial branch and FS (Munroe and Farbrother (1969). In addition, the fate of neighboring bolls at all FS on each sympodium was recorded. This resulted in a complete fruiting map for each plant. Individual harvested bolls were placed into an envelope and stored at 24°C for 30 d. The seedcotton weight of each boll was then determined to within 0.01 g. A total of 15 329 bolls (7531 at FS 1, 5382 at FS 2, and 2416 at FS 3) were harvested. Bolls damaged by insects or boll rot were not used for determination of boll weight, but were considered to be retained bolls that competed with neighboring bolls. Thus, slightly fewer bolls were used in the calculation of average boll weights than boll retention percentages. Fruiting sites distal to FS 3 were collected and weighed but not used because their occurrence was infrequent.

For each FS, the competition level was based on the boll retention data for FS 1, 2, and 3 on each sympodial branch. Numerical values of 1 through 4 were assigned to each of the four levels of competition for each FS. For each boll at all FS, a competition level of 1 means that the boll was the only boll on a given sympodial branch and thus there was no competing boll. A competition level of 4 means that a boll was present at all three FS on a sympodium. Competition from only one additional boll on a sympodium was designated by a 2 or 3 as follows. For a boll at FS 1, 2 = a boll present at FS 2 but not at FS 3 and 3 = a boll present at FS 3 but not at FS 2. For a boll at FS 2, 2 = a boll present at FS 1 but not at FS 3 and 3 = a boll present at FS 3 but not at FS 1. For a boll at FS 3, 2 = a boll present at FS 1 but not at FS 2 and 3 = a boll present at FS2 but not at FS 1.

The experiment design was a randomized complete block with four blocks. The treatment arrangement was a split plot with N rates as main plots, sympodial branches as split plots and the four competition levels for the three FS as split-split plots. Probabilities of boll retention and boll weight were fit using a mixed-models analysis with degrees of freedom estimated using a Satterthwaite approximation (SAS Institute, 1999). Separate models were constructed for each FS. In the original analyses there was little difference in boll retention and weight among adjacent sympodia, so data were combined for sympodia 6 through 8, 9 through 11, 12 through 14, 15 through 17, and 18 through 20. Bolls on sympodia below 6 and above 20 were omitted because their occurrence was low. This procedure reduced the number of treatment means by two-thirds without affecting results.

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Boll Retention Percentage
Fruiting Site 1
The total number of bolls harvested across 4 yr for each of the competition levels at FS 1 was: Competition Level 1, 3644; Competition Level 2, 2407; Competition Level 3, 758; and Competition Level 4, 722. Boll retention at FS 1 was not significantly affected by N rate or sympodia. The primary factors affecting retention were competition and the N rate x competition interaction (Table 1). Effects of FS competition on boll retention are presented and discussed averaged across years by N rate and sympodia.

View larger version (33K): [in this window] [in a new window]   Fig. 1. Boll retention percentage as affected by competition among fruiting sites (FS) within sympodia and fertilizer N rates that range from deficient to excessive, averaged across 4 yr, and sympodia 6 through 20. Competition levels for each FS are as follows: FS 1–C1, solitary boll at FS 1; C2, bolls retained at FS 1 and 2; C3 bolls retained at FS 1 and 3; C4, bolls retained at FS 1, 2 and 3. FS 2–C1, solitary boll at FS 2; C2, bolls retained at FS 1 and 2; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3. FS 3–C1, solitary boll FS 3; C2, bolls retained at FS 1 and 3; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3.

View larger version (32K): [in this window] [in a new window]   Fig. 2. Boll retention percentage as affected by competition among fruiting sites (FS) within sympodia, averaged across 4 yr, and 8 fertilizer N rates. Competition levels for each FS are as follows: FS 1–C1, solitary boll at FS 1; C2, bolls retained at FS 1 and 2; C3 bolls retained at FS 1 and 3; C4, bolls retained at FS 1, 2 and 3. FS 2–C1, solitary boll at FS 2; C2, bolls retained at FS 1 and 2; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3. FS 3–C1, solitary boll FS 3; C2, bolls retained at FS 1 and 3; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3.

In fact, under natural conditions of bud and boll retention, distal bolls on a sympodium would not be expected to greatly affect retention at FS 1 because bolls at FS 1 are 6 and 12 d older than bolls at FS 2 and 3, respectively (Jenkins et al., 1990a). Still, there could be some effect of distal FS on boll retention at FS 1, depending upon the timing of events that affect the fate of fruiting forms at FS 2 and 3. Heitholt (1997), for example, showed that retention at FS 1 increased when FS 2 fruit were removed as floral buds. Early fruit loss such as this would most likely occur from insect feeding rather than from plant stress (Mauney and Henneberry, 1984; Tugwell et al., 1976), but would still provide additional assimilates to FS 1 from leaves subtending FS 2 and 3 (Peoples and Matthews, 1981; Ashley, 1972). Also, as discussed below, the occurrence of distal bolls on a sympodium did affect boll weight at FS 1 and thus the likelihood exists that part of the differences in boll retention at FS 1 were either directly or indirectly related to the fate of distal FS.

Fruiting Site 2
The total number of bolls harvested for each of the competition levels was: Competition Level 1, 1702; Competition Level 2, 2407; Competition Level 3, 563; and Competition Level 4, 710. Boll retention at FS 2 was primarily affected by competition level and to a much lesser extent by N rate (Table 1). Increase in N rate from 28 up to 112 kg ha^-1 increased boll retention. Sympodia had no effect on the boll retention percentage at FS 2. The N rate x competition level interaction was significant but the sympodia x competition level was not significant, indicating that competition effects were similar across sympodia. Boll retention at FS 2 increased on all sympodia when a boll was retained at FS 1 (Fig. 1b and 2b). Boll retention averaged 16% when the FS 2 boll was the solitary boll on the sympodia, but averaged 25% when a boll was retained at FS 1. Boll retention at FS 2 was reduced when bolls were retained at FS 3 or both FS 1 and 3. Much of the reduction in boll retention at FS 2 from Competition Levels 3 and 4 were likely due to the previously mentioned inherent low boll retention at FS 3 (Fig. 1c, 2c) and perhaps not to a direct effect of FS 3 on FS 2. From a total yield standpoint, boll set at FS 1 was beneficial not only for the yield derived from FS 1, but also for enhancing boll number at FS 2.

Previous research has found that, with artificial fruit removal, boll retention at FS 2 is likely to be influenced by the fate of FS 1, because that FS is older and its fate determined several days earlier (Heitholt, 1997; Kerby and Buxton, 1981; Jenkins et al., 1990a). With a boll, FS 1 is a reproductive sink that can compete successfully for assimilates with distal FS on the same sympodium and, lacking a boll, may result in additional assimilate availability to FS 2. The results of the present study were different from earlier studies where fruiting structures were artificially removed in that boll retention at FS 2 was increased by having a boll retained proximal to the site and decreased when bolls were retained distal, or both proximal and distal, to the site. This would be the expected result if boll retention at FS 1 were needed to establish the sympodia as a strong reproductive sink for acropetal transport. Another possibility is that plant health and field conditions conducive to boll set at FS 1 persisted long enough to increase boll set at FS 2. However, since the effects were consistent across sympodia throughout the boll set period, the effect of boll retention at FS 1 on boll retention percentage at FS 2 was not transitional and was therefore likely related to the presence of bolls at FS 1. These results also demonstrate that failure of cotton plants to completely compensate for fruit loss at FS 1 (Heitholt, 1997; Holman and Oosterhuis, 1999) may be partly due to the related lower retention at FS 2 as well as to the inherent smaller bolls at distal FS.

Fruiting Site 3
The total number of bolls harvested for each of the competition levels at FS 3 was: Competition Level 1, 529; Competition Level 2, 710; Competition Level 3, 526; and Competition Level 4, 651. Boll retention at FS 3 was not significantly influenced by N rate, sympodia, or competition level and remained at 6 to 10% regardless of the treatment variable. The presence of bolls at FS 1 and 2 that establish sympodia as a reproductive sink had only small effects in increasing boll retention at FS 3 (Fig. 1c and 2c). Despite the findings by Peoples and Matthews (1981) that assimilates remain in a sympodium unless all bolls are aborted, there was little evidence from these results that the absence of bolls at FS 1 and 2 increased boll retention at FS 3. The assimilates may be used by leaf and stem sinks within the sympodium.

Seedcotton Weight per Boll
Fruiting Site 1
Boll weight ranged from 3.2 to 4.8 g and was significantly affected by N rate, sympodia, and FS competition (Table 2). The variable that had the largest effect, by far, was FS competition. The N rate and sympodia main effects, although significant, were small in comparison to the effects due to competition among FS. Significant interactions included competition level x sympodia and N rate x sympodia. The N rate x competition level interaction was not significant.

View larger version (62K): [in this window] [in a new window]   Fig. 3. Seedcotton weight per boll as affected by competition among fruiting sites (FS) within sympodia and fertilizer N rates that range from deficient to excessive, averaged across 4 yr, and sympodia 6 through 20. Competition levels for each FS are as follows: FS 1–C1, solitary boll at FS 1; C2, bolls retained at FS 1 and 2; C3 bolls retained at FS 1 and 3; C4, bolls retained at FS 1, 2 and 3. FS 2–C1, solitary boll at FS 2; C2, bolls retained at FS 1 and 2; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3. FS 3–C1, solitary boll at FS 3; C2, bolls retained at FS 1 and 3; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3.

View larger version (58K): [in this window] [in a new window]   Fig. 4. Seedcotton weight per boll as affected by competition among fruiting sites (FS) within sympodia, averaged across 4 yr, and 8 fertilizer N rates. Competition levels for each FS are as follows: FS 1–C1, solitary boll at FS 1; C2, bolls retained at FS 1 and 2; C3 bolls retained at FS 1 and 3; C4, bolls retained at FS 1, 2 and 3. FS 2–C1, solitary boll at FS 2; C2, bolls retained at FS 1 and 2; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3. FS 3–C1, solitary boll at FS 3; C2, bolls retained at FS 1 and 3; C3, bolls retained at FS 2 and 3; C4, bolls retained at FS 1, 2 and 3.

Fruiting Site 2
Competition level, sympodia, and N rate significantly affected boll weight at FS 2, which ranged from 2.7 to 4.3 g. Fruiting site competition level elicited the largest boll weight response (Table 2). The N rate x sympodia interaction was significant because increase in N rate increased total seedcotton at apical and distal sites (Boquet et al., 1994). This interaction did not affect competition among FS and the N rate x competition level interaction was not significant. There was also no significant interaction between sympodia and competition level indicating that competition effects on boll weight were similar across sympodia.

Boll weight responses at FS 2 followed a somewhat different pattern than boll retention. Retention of a boll at FS 1 consistently decreased boll weight at FS 2 (Fig. 3b, 4b). The response was similar across the 4 yr and resulted in an average reduction in boll weight at FS 2 of 0.35 g. These results are consistent with previous research that showed that competition between FS 1 and FS 2 reduced boll weight at FS 2 (Jenkins et al., 1990a; Heitholt, 1997). When ambient conditions were such that boll retention could occur at FS 3, however, boll weight at FS 2 and 1 increased compared with having bolls only at FS 2 or at FS 1 and 2. Thus, having a proximal competing boll reduced boll weight at FS 2, whereas having a distal or both distal and proximal boll increased boll weight. As in the case of boll weight at FS 1, the explanation for these responses lie with the naturally occurring conditions that were favorable enough to promote boll retention at distal FS. Such conditions also enhanced the source and sink strength and thus boll development at all FS of the sympodium. This thesis is further supported by the increase in boll weight at FS 1 when additional bolls were retained on the sympodia, an occurrence that would not be expected to directly affect FS 1. These findings along with those of Peoples and Matthews (1981) and Ashley (1972) support the concept that assimilate distribution among FS within a sympodium can be a mutually beneficial process. These results also agree with those of Heitholt (1997) who noted that retention of multiple bolls on a sympodium was necessary to produce maximal yield.

Fruiting Site 3
Boll weight at FS 3 was influenced by fertilizer N rate and competition level. The N rate x sympodia was the only significant interaction effect. Boll weight at FS 3 was smaller than at FS 2 and ranged from 2.7 to 3.5 g. In contrast to boll retention at FS 3, there were notable effects of competition level on boll weight (Fig. 3c, 4c). These effects, however, were not as consistent for FS 3 as for FS 1 and 2, which probably reflects a greater dependency of this most distal FS on both plant condition and ambient environment. The overall tendency was for increased competition to decrease boll weight at FS 3. Boll weight was largest when FS 3 retained the sole boll on a sympodium and least when all three bolls on the sympodium were retained.

Bolls as distal as FS 3, therefore, had some influence, but not a major influence, in increasing the sink strength of sympodia. Bolls at FS 3 also benefited from acropetal transport from subtending leaves at FS 1 and 2 when fruiting structures at those sites aborted. These results disagree with the findings of Peoples and Matthews (1981) and Ashley (1972) that the only direction for transport of assimilates in sympodia is basipetal. Although having a lone boll at FS 3 did not consistently reverse the predominance of this effect, in some situations FS 3 did benefit from fruit loss at proximal FS.

	SUMMARY

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Large reciprocal effects among bolls on a sympodial branch were common and affected the outcome for boll retention and weight, but these interactions were not necessarily detrimental to individual bolls or yield. Although FS on each sympodium are usually thought of as competing sites, source–sink relationships among FS on sympodia of cotton plants often had favorable rather than adverse effects on boll retention and boll weight. A favorable outcome for one boll often leads to favorable outcomes for other bolls on any given sympodium. The only exception was that boll retention at FS 1 caused a reduction in weight of bolls at FS 2 when no boll was present at FS 3. Nitrogen fertility level and location of the sympodium were not critically important to these outcomes.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Manuscript no. 01-76-0618.

Received for publication December 4, 2001.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 

• Ashley, D.A. 1972. ¹⁴C-labeled photosynthate translocation and utilization in cotton plants. Crop Sci. 12:69–74.
• Bartholomew, R.P., and G. Janssen. 1928. Effect of fertilizers on the size of cotton bolls. J. Am. Soc. Agron. 20(10):1048–1054.
• Benedict, C.R., and R.J. Kohel. 1975. Export of ¹⁴C-assimilates in cotton leaves. Crop Sci. 15:367–372.[Abstract/Free Full Text]
• Boquet, D.J., E.B. Moser, and G.A. Breitenbeck. 1993. Nitrogen effects on boll production of field-grown cotton. Agron. J. 85:34–39.[Abstract/Free Full Text]
• Boquet, D.J., E.B. Moser, and G.A. Breitenbeck. 1994. Boll weight and within-plant yield distribution in field-grown cotton given different levels of nitrogen. Agron. J. 86:20–26.[Abstract/Free Full Text]
• Constable, G.A. 1991. Mapping the production and survival of fruit on field-grown cotton. Agron. J. 83:374–378.[Abstract/Free Full Text]
• Ehlig, C.F., and R.D. LeMert. 1973. Effect of fruit load, temperature, and relative humidity on boll retention of cotton. Crop Sci. 13:168–171.
• Gerik, T.J., W.D. Rosenthal, C.O. Stockle, and B.S. Jackson. 1989. Analysis of cotton fruiting, boll development, and fiber properties under nitrogen stress. p. 64–67. In Proc. Beltwide Cotton Res. Conf., Nashville, TN. 2–7 Jan. 1989. Natl. Cotton Council Am., Memphis, TN.
• Guinn, G. 1982. Causes of square and boll shedding in cotton. USDA Tech. Bull. No. 1672. U.S. Gov. Print. Office, Washington, DC.
• Heitholt, J.J. 1997. Floral bud removal from specific fruiting positions in cotton: Yield and fiber quality. Crop Sci. 37:826–832.[Abstract/Free Full Text]
• Holman, E.M., and D.M. Oosterhuis. 1999. Cotton photosynthesis and carbon partitioning in response to floral bud loss due to insect damage. Crop Sci. 39:1347–1351.[Abstract/Free Full Text]
• Jenkins, J.N., J.C. McCarty, Jr., and W.L. Parrott. 1990a. Fruiting efficiency in cotton: Boll size and boll set percentage. Crop Sci. 30:857–860.[Abstract/Free Full Text]
• Jenkins, J.N., J.C. McCarty, Jr., and W.L. Parrott. 1990b. Effectiveness of fruiting sites in cotton: Yield. Crop Sci. 30:365–369.
• Jones, M.A., R. Wells, and D.S. Guthrie. 1996. Cotton response to seasonal patterns of flower removal: II. Growth and dry matter allocation. Crop Sci. 36:639–645.[Abstract/Free Full Text]
• Kerby, T.A., and D.R. Buxton. 1981. Competition between adjacent fruiting forms in cotton. Agron. J. 73:867–871.[Abstract/Free Full Text]
• Mauney, J.R., and T.J. Henneberry. 1984. Causes of square abscission in cotton in Arizona. Crop Sci. 24:1027–1030.[Abstract/Free Full Text]
• Moore, S.H. 1999. Nitrogen effect on position of harvestable bolls in cotton. J. Plant Nutr. 22:901–909.
• Munroe, J.M., and H.G. Farbrother. 1969. Composite plant diagrams in cotton. Cotton Grow. Rev. 46:261–282.
• Peoples, T.R., and M.A. Matthews. 1981. Influence of boll removal on assimilate partitioning in cotton. Crop Sci. 21:283–286.[Abstract/Free Full Text]
• Pettigrew, William T. 1994. Source-to-sink manipulation effects on cotton lint yield and yield components. Agron. J. 86:731–735.[Abstract/Free Full Text]
• Reddy, R.N., and R.S. Rao. 1970. Effect of different levels of nitrogen and spacings on the yield of ‘RPS 72’ cotton (Gossypium hirsutum L.). Indian J. Agric. Sci. 40:356–359.
• SAS Institute. 1999. Proprietary software release 8.2. SAS Inst., Cary, NC.
• Tugwell, P., S.C. Young, Jr., B.A. Dumsas, and J.R. Phillips. 1976. Plant bugs in cotton: Importance of infestation time, types of cotton injury, and significance of wild hosts near cotton. Rep. Ser. 227. Arkansas Agric. Exp. Stn., Fayetteville, AR.
• Turner, J.H., Jr. 1944. The effect of potash level on several characters in four strains of upland cotton which differ in foliage growth. J. Am. Soc. Agron. 36:688–698.
• Wadleigh, C.H. 1944. Growth status of the cotton plant as influenced by the supply of nitrogen. Bull. 446. Arkansas Agric. Exp. Stn., Fayetteville, AR.

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