PHYSIOLOGICAL STUDIES OF POTATOES, SOLANUM TUBEROSUM L., GROWN IN ARIZONA (WATER STRESS, SUGARS AND STARCH, CARBOHYDRATE, BARLEY, POLLEN).

Abstract

The physiological development of potato plants and tubers grown in Arizona desert regions were examined and spectrophotometric methods were developed for the analysis of carbohydrates in potato tubers, pollen, and leaf tissues from various plants. Seed pieces were planted (March 1979, 1980) and harvested (June, July) in 2 locations. Emergence, tuber initiation, and maximum tuber numbers occurred 3, 5, and 10 weeks, respectively, after planting. In 1979, tuber yields in Mesa were low because of a shortened growing season; in Tucson, yields were drastically reduced because of soil water-logging. In 1980, tubers were planted in Mesa (March 5) and yield of the cultivar 'Kennebec' was higher, 'Denali' was nearly equal to whereas 'Norgold Russet' was lower than the national average for the respective cultivars. 'Kennebec' had the highest leaf area index (LAI) and plant height. Plantings in Marana (March 21) had lower LAI and plant height than in Mesa and yielded less, but rankings of cultivars for yield were the same. During rapid tuber growth, air temperatures often exceeded 40°C, but lower canopy temperatures were 30°C or lower, and water potentials (ψ) were -9 bars or higher. Chemical analysis showed tubers increased starch percentages during development, and levels at maturity were similar to those found in other regions of the country. Extracts for carbohydrate analysis were obtained by overnight immersion in 80% ethanol and total soluble sugars (TSS) were analyzed by an improved anthrone assay and also with para-hydroxybenzoic acid hydrazide (p-HBAH) following methylation and permanganate oxidation. Methods were also developed for estimating total keto sugars with phenol in acetic/sulfuric acid (PASA) and also with thiobarbituric acid (TBA). Aldohexoses were determined with o-toluidine and o-ethylaniline; total reducing sugars were analyzed with p-HBAH, and sucrose was estimated with anthrone or PASA or TBA following alkaline enolization or borohydride reduction of monosaccharides. Starch was determined quantitatively after enzymatic hydrolysis to glucose and analyzing with anthrone, o-toluidine, or p-HBAH. Potential errors involved in the methods are discussed and the techniques were applied to carbohydrate analysis in plant tissues and pollen.