01491naa a2200193 a 450000100080000000500110000800800410001910000180006024502090007826000090028752008580029665000120115465000110116665300190117765300120119665300150120870000180122377300560124116481832023-04-17       1953    bl uuuu     u00u1 u    #d1 aWATSON, D. J.  aComparative phusiological studies on the growth of field cropsbthe effect of infection with beet yellows and beet mosaic viruses on the growth and yield of the sugarbeet root crop.h[electronic resource]  c1953  aInfection with beet yellows virus depressed the dry-matter yield of sugar-beet plants by decreasing both leaf area and net assimilation rate (N.A.R.). It did not reduce the number of leaves. the lower N.A.R. of infected plants may occur because photosynthesis is slowed by chlorosis of the leaves or by changes associated with it. plants infected at the end of june had 30-50% of their leaf area yellowed from mid-august. later infection caused less yellowing. the yellowing almost sufficed to account for the decrease in N.A.R., if yellowed parts of leaves do not photosynthesize. however, the similar diurnal fluctuations of carbohydrate in the laminae of healthy and infected leaves suggests that photosynthesis may not be much slowed by infection; if so, the decrease in N.A.R. indicates a large increase in respiration rate, especially of the root.  aDoença  aVírus  aCana-de-acucar  aDisease  aSugar-cane1 aWATSON, M. A.  tAnnals of Applied Biologygv.40, n.1, p.1-37, 1953.