Although seed vigor is ultimately expressed in terms of growth, it is not clear if metabolic processes unlinked to growth can also estimate vigor. The objective of this study was to determine if the relationship between seed vigor and ethanol metabolism differed depending on whether seed growth was presence or absence. For individua1 imbibed cotton seed, ethanol assimilation in air and ethanol biosynthesis in N₂ gas was correlated to seed vigor as measured by cool test performance. Seed growth in N₂ gas was prevented by the addition of polyethylene glycol. Results were inconclusive, because seed performance (radicle growth) during cool testing was not significantly correlated to either ethanol biosynthesis or ethanol assimilation. It was concluded that ethanol metabolism both in the absence and presence of seed growth has limited usefulness as a metabolic marker of cotton seed vigor.

The effects of oxygen stress and water stress on cotton seed radicle growth was studied. High vigor Deltapine 90 seed were imbibed in individual test tubes at 28°C for 28 hours. Seed were then subjected for 2 hours at 28°C to either 1) oxygen stress imposed by N₂ gas, 2) water stress imposed by polyethylene glycol 6000 (0.8 gm mL water⁻¹), or 3) a combination of both 1) and 2). Following imposition of either oxygen stress or water stress, radicle growth stopped temporarily; growth resumed while either stress was still imposed but at a greatly reduced rate relative to the unstressed control. Cotton radicle growth was prevented however, in the presence of both oxygen and water stress. The prevention of growth was reversible, as growth resumed when both stresses were relieved.

Responses to environmental stresses such as excess salinity are difficult to understand if not studied under defined conditions. The objective of this study was to determine if cottonseed radicle and cotyledon growth during germination was affected by exogenous NaCl. Cottonseeds were imbibed in moistened paper toweling for 24 h at 32°C before transfer to an agar media containing selected concentrations of NaCl for an additional 24 h. Radicle linear growth extension was stimulated at low NaC1 concentrations (80 mM), but increasingly inhibited as NaCl concentrations increased from 160 to 400 mM. Radicle and cotyledon fresh weights were increasingly inhibited by NaCl concentrations between 0 and 400 mM. NaCl inhibition of radicle fresh weights was more pronounced than that of cotyledons. We conclude that the inhibitory effects of NaCl can be quantified as reductions in cottonseed radicle and cotyledon growth.

The accumulation of proline (Pro) in plants during NaCl stress may have adaptive significance and the study of this response could reveal a genetic strategy for enhancing NaCl tolerance. Our objective was to determine if the Pro content of germinating cotton seeds is altered by exposure to exogenous NaCl. Seeds were imbibed for 24 h at 32°C before transfer to agar media containing NaCl. After 24 h of NaCl exposure, the Pro contents of radicles and cotyledons were measured using a colorimetric assay. Results showed that Pro contents of both radicles and cotyledons increased as the level of NaCl increased. The bulk of Pro content increases were restricted to the radicle and occurred in the range of NaC1 concentrations from 200 to 400 mM NaCl.

The adaptive significance of proline (Pm) accumulation in cotton seeds can be assessed by determining if NaCl tolerance is influenced by changes in the Pm level of the seed. The objective of this study was to determine if exogenous L-Pro and D-Pro reduce NaCl inhibition of radicle growth of germinating cotton seeds. Seeds were imbibed for 24 h at 32°C before transfer to agar medium containing either Pro, NaCl or mixtures of both. Results indicate that exogenous Pro increases the Pro contents of cotton seed radicles and cotyledons to a similar extent. Such increases are independent of whether L- or D-Pro is fed exogenously. Results also show that exogenous Pro does not significantly reduce NaCl inhibition of radicle growth in germinating cotton seeds. .

Field experiments were conducted at four locations in Arizona (Yuma, Maricopa, Marana, Safford) to evaluate 16 cottonseed treatments on cotton that included 12 on Upland (Q. hirsutum L.) and 4 on Pima (Gossvpium barbadense L.). Stand counts were taken to evaluate the effectiveness of each treatment. Statistical analysis showed no significant differences among the treatments used for the Upland cottonseed. Significant differences were found among the treatments used for the Pima cotton seed at the Marana and Safford locations only.

A number of representative seed lots of both upland and Pima cotton cultivars and experimental strains have been evaluated utilizing two instruments which measure relative seed coat strength. Seed coat strength was found to have a strong genetic component of determination, with relatively minor influence of environment and year of production being observed Greater seed coat strengths should contribute to the relative resistance to seed damage and cracking during picking ginning and conditioning operations. It may be possible to incorporate this trait into cotton cultivars by mass selection techniques.

Field experiments were conducted at three locations in Arizona (Maricopa, Marana, Safford) to evaluate 12 cottonseed treatments on Upland cotton (G. hirsutum L.). Stand counts were taken to evaluate the effectiveness of each treatment. Statistical analysis showed no significant differences among the treatments used at the Marana location. Significant differences were found among the treatments used at the Maricopa and Safford locations.

We evaluated an array of progeny of interspecific cotton crosses in the field. Significant water stress was placed on the plants in mid-summer by withholding water supplied by drip irrigation during plant development earlier in the season. A number of physiological measurements were carried out on selected individual plants of this population during the several week period of imposed drought stress. Overall results confirm that a large degree of variation exists within the population for all traits measured. Initial carbon isotope discrimination measurements suggest this trait may prove useful in estimating transpiration efficiency of cotton genotypes.

The germination percentage and seedling respiration were evaluated on 11 cultivars of Cotton produced in Arizona. Respiration rates of 5-day old seedlings ranged from 6.0 to 16.9 mg /g⁻¹ hr⁻¹ for DP -5690 and KC-311, respectively. Germination percentage ranged from 31 to 87% for KC-311 and DP-51, respectively. A significant negative correlation (r = -.90) between respiration rates and the germination percentage indicates that seed quality is closely associated with early seedling metabolic rates.