Indices of amounts of weather fleck were evolved from field inspections of flue-cured tobacco subjected to variable amounts of irrigation water. The susceptibility of tobacco leaves to weather fleck increased with maturation, reaching a maximum when they became mature. Occurrence and intensity of the disorder were found to be directly related to amounts of incident water, which hastened leaf maturity and rate of plant growth.

Chlorine frorn 20 ,o so poo,*3fffilt* no efiecr on yield or teafgrade quality of flue-cured tobaccogrown.on a Fox loamy sand. Incleased applications of chlorine increased the cltlorine content, moisture uptake.and decreased the rate of bum of the cured leaf trut had no elTect oh the amount of total sugars. INTRODUCTIONUnder ordinary conditions chlorine is readily absorbed from the soil by a tobacco plant. Vickery et al. (10)

Maleic hydrazide applied to flue-cured tobacco at topping time at five different rates, ranging from 0.75 to 3.75 pounds of the actual chemical per acre, increased the total sugar and reducing sugar content throughout the plant. The total alkaloid content in the upper part of the plant was decreased more by low rates than by high rates of the applied chemical. The total ash, calcium, magnesium, phosphorus and chlorine content was reduced in the upper part of the treated plant, whereas the potassium content was not affected.

ABSTRACT

Effects of temperarure during the yellowing phase of the curing process on the quality of tobacco leaves of the flue-cured type were studied in small chambers, temperature and moisture being precisely controiled. With multi-stage (conventional) schedules, whereby temperature was increased by increments of 5 and 10'F. within the range of 80 to 110"F., the leaf quality was equivalent to that obtained from a two-stage schedule, in which 90'F. was maintained for 24 hours and 105'F. for the rest of the yellowing phase. Both procedures gave only slightly higher quality rhan single-stage schedules in the range of 95 to 105"F. Tobacco which yeilowed at rcmperatures outside the latter range, especially below 90'F. and above 110"F., had comparatively low quality. The temperature response was practically unaflected by variations in saturation deficit up to 75 grains of moisrure per pound of dry air.to 110"F. coincides with a sradual decrease in relative humidity from 100 to 60 per cent. However, b"ecause of the inadequacy of facilities" for precise control within the ranges indicated above, information has been lacking on the effects of variationi in temperarure or moisture on the qualiry of ianadian flue-cured tobacco. Small chambers, conditioned with forced air, provide the precise control required for such studies. Previous investigations' showed that the leaf quality obtained in kilns equipped with a forcedair svstem was eouivalent to that obtained with a natural convection (conventional) system. lContribution No. 23, Reseach Harrow, Ont. 2Walker, E. K., ancl ]. Williams. Research Foundation, Toronto, Ont. Station, Research Branch, Canada Department of Agriolfure, Tobaeo curing investigations in 1955. Research rept., Onttrio Unnublished. 780 Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 44.224.250.200 on 07/04/20 For personal use only.\ Can. J. Plant Sci. Downloaded from www.nrcresearchpress.com by 44.224.250.200 on 07/04/20 For personal use only.