Mep Plus – A Newly Registered PGR

ABSTRACT
MepPlus is a premix of Mepiquat Chloride and Bacillus cereus (BP01). It gained full EPA registration in 1997 for use on cotton. The B. cereus component has a tolerance exemption on all crops. MepPlus was extensively tested by university researchers across the US cotton belt in 1996 and 1997. It provides both significantly higher lint yield and more consistent yield increases than Mepiquat Chloride alone while producing the same degree of earliness and growth control. It was introduced in the US commercially late in the 1997 season. Yield results and preliminary information on the possible mode of action are provided.

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Effect of Four Growth Regulators

ABSTRACT
The effect of four plant growth regulators (PGRs) on crop performance, fruiting pattern, yield and fiber quality in cotton (Gossypium hirsutum L.) was evaluated in field experiments for two years in Greece. All four PGRs (Cytokin, Cytoplex, PHCA and Atonic) increased seedcotton yield and differences were related to effects on plant growth and development. Number of sympodia with 2 bolls and total boll number increased significantly in the Cytokin and Cytoplex treated plants, while Atonic and PHCA had a lesser effect. All PGRs increased boll retention, either at first or at second position. Lint quality was not affected by PGRs, although in some experiments positive effects were found in fiber maturity and strength. It is concluded that the four PGRs have the potential to control plant growth and enhance yield.

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PGR IV Increased Cotton Yield by Affecting Various Fruiting Parameters

ABSTRACT
The effect of the plant growth regulator PGR-IV on cotton (Gossypium hirsutum) was evaluated in field experiments in up to eight locations, for three years (1995-97) in Greece. Seedcotton yields were increased by up to 20 % in most locations, compared to the control. The mean yield increase in all locations and years was 4.9%. This was correlated with increases in boll retention, number of sympodia with two bolls and total boll number per plant. Late PGR-IV applications had no significant effect on seedcotton yield, compared to the PGR-IV treatment with three applications. No effect was found in plant height and fiber quality parameters. It is concluded that PGR-IV can increase seedcotton yield by affecting plant performance.

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Heat Tolerance of Cotton Genotypes Assessed by Electrolyte Leakage, Chlorophyll Fluorescence Analysis and Performance in the Field in Pakistan

ABSTRACT
Germination and emergence of 117 cotton accessions were tested in the laboratory at 43oC and 30oC. The absolute heat tolerance of detached leaves of the 117 accessions was tested by chlorophyll fluorescence analysis (CFA) and by electrolyte leakage tests. The heat tolerance of whole plants was examined in a large, modified growth chamber. The relationships between temperature, net photosynthesis, stomatal conductance, transpiration and transpirational leaf cooling were examined using an automated CIRAS infra-red gas analyzer to measure gas exchange parameters while applying defined profiles of increasing leaf temperatures. An early-sowing field experiment at Multan examined the responses of 16 cotton lines to early heat stress. CIM443, CIM 438, BH89, GH8, NIAB78 SLS1 and 1269/93 were more heat-tolerant than Acala SJ2 at the germination stage. The chlorophyll fluorescence assay (CFA) revealed that CIM448 and CIM435 performed better than CIM443, but SLS1 performed badly in CFAs. Of the wild species, G. sturtianum was least tolerant, while Thespesia populnea was the most heat-tolerant wild relative. The hexaploid G411 (G. hirsutum cv. NC8 x G. australe) was the most tolerant interspecific hybrid. Electrolyte leakage tests largely confirmed these results. CIM448 and NIAB 313 were less leaky than Acala SJ2, while DNH40 was susceptible to heat damage. Only the electrolyte leakage test gave data which correlated well with yields in the field experiment.

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Glycinebetaine Treatment Improves Cotton Yields in Field Trials in Pakistan

ABSTRACT
This study was designed to test the effectiveness of glycinebetaine (an osmoprotectant purified from sugar beet and applied as a spray of ‘Greenstim’) in improving the yields of cotton under normal cultivation conditions in the Punjab of Pakistan. Field trials were conducted in replicated small plots at two sites over two years to determine the optimal timing and dose of glycinebetaine. CIM-240 was sown in 1996 at the Postgraduate Agricultural Research Station (PARS), Faisalabad but was badly affected by whitefly and cotton leaf curl virus. CIM-443 was sown in 1996 and 1997 at the Central Cotton Research Institute (CCRI), Multan. This was resistant to leaf curl virus, and was sown at PARS in 1997. Generally, glycinebetaine concentrations and time of application had little effect on physiological parameters. In 1996, glycinebetaine concentrations were significantly increased in the trial at Faisalabad, but not at Multan. In 1996 the highest yield of seed cotton at Faisalabad (136 % of the control) was obtained with 3-kg/ha glycinebetaine applied at squaring. At Multan, seed cotton yields were highest with 3 and 6 kg/ha glycinebetaine applied at squaring. Glycinebetaine dose and time of application had highly significant (P<0.001) effects on yield, total dry matter and bolls per plant. Glycinebetaine-treated plants also had more nodes at maturity than the controls. Mean boll weight, % flower and boll shedding were not affected. In 1997 the highest yields were obtained when glycinebetaine was applied at first flowering at PARS, but at the pre-squaring stage at CCRI.

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Exogenously-Applied Glycinebeyaine is Not Rapidly Re-Translocated in Cotton

ABSTRACT
The redistribution of methyl-14C-glycinebetaine was examined after local application to young cotton plants at first flowering. Labelled glycinebetaine in a solution containing Tween-20 (0.05%) was applied to the surface of young or old leaves of cotton (cv. CIM-443) using a syringe. In some cases a self-sealing plastic bag was used to maintain high humidity around the fed leaf. Plants were subsequently grown for 7-10 days in a greenhouse or in a controlled-environment room. Fed leaves were carefully washed prior to sampling. Movement of label was detected in three ways. Plants dried 5 days after treatment and subjected to autoradiography for 5 days showed concentrated labelling in the fed leaf, with lower activity in the attached petiole and the adjacent stem. Long-distance transport of label (as happens in rapeseed etc.) was not observed. More quantitative data were obtained by dividing the plants into stem, petioles, leaves and sympodial branches, drying the samples and burning them in a sample oxidizer. This confirmed that there was little movement of label to other main-stem leaves or to the shoot apex, but some movement into the adjacent main stem and sympodial structures. In these experiments it is assumed that glycinebetaine is not easily metabolized in cotton, and remains in solution. Extraction of sap from different parts of the plants produced a similar pattern of label distribution to sample oxidation. Only when methyl-14C-glycinebetaine was directly injected into a petiole was there substantial movement of label – mostly into the attached leaf and the adjacent stem.

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Post application Environment Controls Growth Responses in Cotton

ABSTRACT
RyzUp is a gibberellic acid-based plant growth promoter for cotton. The objective of this study was to determine whether growth responses of cotton to RyzUp application depend on post-treatment environmental conditions defined by temperature and potential evapotranspiration. The experiments were conducted at the Texas A&M University Agricultural Research and Extension Centres in Corpus Christi and Uvalde, TX, during the 1996 and 1997 seasons. Results showed that the cotton’s growth responses to RyzUp depended strongly on year, location and timing of application within year. Responses of both plant height and number of fruiting positions to RyzUp appeared to be inversely related to cumulative atmospheric water demand during the 15 days following treatment. Practical implications of this finding point towards possible fine-tuning the management of RyzUp application, depending on prevailing or near-future weather conditions.

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Utilization of Spectral Imaging to Detect N and K Sufficiency in Cotton

ABSTRACT
Nitrogen and K as well as other plant nutrients influence the spectral properties of individual crop leaves and plant canopies. Technology is currently available that can measure reflectance at spectral resolutions of less than 2 nm. Thus, the identification of specific changes in spectral reflectance relative to plant nutrient concentration may be possible. Field studies with variations in soil K availability and N fertilization were used to study spectral reflectance properties of individual leaves and plant canopies influenced by plant nutrition. Leaf samples at different stages of plant development were used to determine the N and K status and their relationship to spectral images and reflectance measurements. Aerial images were taken at 1067 m. with four digital cameras equipped with narrow band pass filters. Bands used were green at 540nm, red at 695 nm and near infra red at 790nm and 840 nm. Leaf and canopy reflectance were measured with a spectro-radiometer that scanned from 350 nm to 1050 nm with a special resolution of 1.6 nm. Aerial imaging was useful in identifying N and K stress anomalies. Crop health varies with N and K nutritional status, suggesting that aerial imaging would be a useful tool in directing producers to problem areas. Correlations were found between leaf N and K concentrations and spectral reflectance at certain wavelengths and growth stages, suggesting that remote sensing at a high degree of spectral resolution may be able to assist in the identification and mapping of field scale variability in N and K nutritional status.

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Spectral Data Analysis for Cotton Growth Monitoring

ABSTRACT
Since information technology was introduced in agriculture, there has been a great deal of interest in estimating terrestrial biophysical parameters such as vegetation with remotely sensed data. The empirical study presented in this paper focuses on the relationships between vegetation properties and reflectance measured on a cotton canopy throughout its phenological evolution by means of a hand-held spectroradiometer, during a field experiment. The objective was to produce relationships between spectral indices (such as normalized difference vegetation index (NDVI)) and biophysical parameters, such as leaf area index (LAI) and biomass that should be useful for cotton studies from remotely sensed data. The NDVI and the other spectral transformations were found useful to describe some phenological stages for a cotton canopy, because of the statistically significantly correlation with biophysical parameters such as LAI and biomass. Coefficients of determination (r2) for the various relationships ranged in statistically significant levels (0.82-0.96) with leaf area index and better estimation of biomass from vegetation indices by exponential equations. The results show that estimated crop values agree well with field observations and there is a potential in applying this approach on an operational basis in practice with multitemporal remote sensing data.

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Cotton Phenology and Growth Processes: Model Development

ABSTRACT
In cotton, phenology and leaf area development are major determinants of final yield, and are substantially affected by temperature when other conditions are optimum. Here the rate functions for various phenological events and leaf area development are presented, providing appropriate information how to develop physiologically-based subroutines for those processes as functions of temperature.

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