In a preliminary, unreplicated test, cotton was planted in 40 inch and 27 inch rows on April 10 and again on May 1. Narrow rows outyielded 40 inch rows at both planting dates. The yield difference between the row spacing treatments was greatest in the May 1 planting. Both row spacings had higher yields when planted on the later date, as did both the DPL 90 and ST506 varieties used in the test.

A breeding program aimed at increasing the ability of long and short staple cotton strains to emerge in saline soils under cool springtime soil conditions has now completed the second cycle of selection. Cycle II emergence results show evidence of progress.

Six different seed treatments and one in furrow granular treatment were used in a field with a history of black root rot, caused by Thielaviopsis basicola. The treatment was a follow-up on the study done the previous year (1). Stand counts, root lengths and seed cotton yields were taken to see if any of the treatments increased stand counts or stimulated root growth. Thielaviopsis was not isolated in the plants this year, so the effect of the fungicides on this pathogen were not evaluated. Stand counts were, however, significantly influenced by the seed treatments.

Ethanol and acetaldehyde production by cotton seeds subjected to anoxic stress imposed by CO₂ or N₂ gas was quantified during the imbibition phase. Fermentation capacity was low in dry seeds and quickly increased during the first few hours of imbibition. In hydrated seeds, ethanol and acetaldehyde excretion following anoxic stress followed a linear trend in time. Ethanol excretion exceeded that of acetaldehyde by an order of magnitude. Similar rates of production were observed whether anoxic was imposed by either CO₂ or N₂ gas. Excreted ethanol and acetaldehyde were rapidly metabolized following alleviation of anoxic stress.

Leakage of reducing sugars and amino acids during cotton seed imbibition was evaluated as a possible vigor test. Seed samples from a single cotton seed lot were subjected to accelerated aging at 46°C and 100% R.H. for up to 216 hours. Aged seeds were imbibed at optimal and suboptimal temperatures, and the leakage of total reducing sugars and amino acids into the imbibition solution was quantified spectrophotometrically. Leakage of seed reserves was positively correlated with the duration of accelerated aging, in terms of subsequent germination performance at 30°C and of similar quantity at both imbibition temperatures.

Anoxic -induced fermentation was evaluated as a potential cotton seed vigor test. Seed samples from a single seed lot were subjected to accelerated aging for different durations to create five classes of seeds on the basis of vigor. The ethanol and acetaldehyde excreted from seeds from each class during brief periods of anoxia was quantified by gas-liquid-chromatography. Ethanol and acetaldehyde production during anoxia was negatively correlated with standard germination test results of all seed samples receiving accelerated aging. The fermentation capacity of hydrated cotton seeds remained intact at imbibition temperatures, which significantly reduced radicle growth.

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.