Sunzinary. Studies The concept of intraspecific variation in mineral element acctnmuilation in plants has only recently been recognized in its broad scope. The wide ranige of variations observed, and the problems and opportninities which this variation presents, have been treated by several anithors (4,5,11,14). A better understanding of the morphological characteristics and physiological processes which affect (lifferential ion accuimuilation among plant genotypes wouild be uisefuil in breeding for desired levels of various elements and in stuidies of the physiological and biochemical bases of mineral accutmuilation in plants.Several workers have fouind that roots are the site of physiological processes leading to differential accuimuilation of minerals in the above-groind parts of plants (1,2,6,8,9,10). Grafting experiments with several plant species have shown that accumulation of variouis elements in the scion was related to the rootstock to which it had been grafted

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that these cultivars do respond to photoperiod with some of the characteristics of short -day plants.These studies were designed to determine the effects of photoperiod and of light and temperature preceding and during the dark period on floral initiation in Pima cotton.

The relationship of number of seed/boll to other yield components and fiber quality of two cultivars of Pima cotton (Gossypium barbadense L.) was investigated as part of a study of the effects of environment on the variability of these cultivars in three tests. A fourth test had only one cultivar. Bolls examined contained from 1 to 31 seed. Environment of the four tests strongly influenced the proportion of bolls in the different seed number classes. Plants grown under favorable production conditions, such as lower summer temperatures, productive soil, and a wet irigation regime, produced a higher percentage of large bolls (more seed) than those grown less favorable environments. Cultivars did not differ in seed/boll. An increase in the number of seed/boll was associated with the following: decreased mean seed wt, increased lint wt/seed, decreased fiber length and uniformity, and increased micronaire, but strength was unaffected. The unexpected increase in lint wt/seed with a decrease in seed size can be explained by the observed concomitant increase in fiber coarseness.

Floral induction in American Pima cotton, (Gossypium barbadense L.), cultivars ‘Pima S‐3’ and ‘Pima S‐4’, occurred earlier (at lower node levels on the main stem) under short winter days than under long summer days when plants were grown under natural light and a controlled temperature program.The intensities of red and far red light in natural sunlight were measured to determine if there were daily or seasonal changes in spectral quality that might be related to variations in floral initiation. Red light predominated during the day, but the balance shifted to a predominance of far red light between sunset and darkness. This relationship was not seasonal.Total exclusion of all light from plants during the 1.5‐hour period before sunset accelerated floral induction if the temperature during this period was above 30 C, but either had no effect or retarded induction if the temperature was below 30 C. Shortening or interrupting the natural dark period with low intensity lights of different spectral composition retarded induction. The intensity of blue light, but not red or far red light, appeared to be related to induction. The increase in the node number of the first fruiting branch was almost directly proportional to the time interval between sunset and the interruption of the dark period.Floral induction was most sensitive to photoperiod and to high temperatures during sunset during the 2nd week of development after germination.