Comparative Physiological Studies on the Growth of Field Crops

Abstract

Infection 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. The effects of yellows on leaf area and N.A.R. appear to be independent; late‐sown plants suffered a greater reduction of leaf area, but a smaller reduction in N.A.R., than early‐sown plants; similarly treated plants showed the same reduction of leaf area in two successive years, but the decrease in N.A.R. was much greater in the second. Most of the loss of dry matter was in the root; the dry weight of the petiole (including stem tissue) was also decreased but the dry weight of leaf lamina was little affected. Yellows greatly increased the reducing sugars in the leaf lamina, and caused smaller increases in sucrose and starch. These effects appeared when the leaves showed only etch symptoms. The increase in starch was greatest at this time, but the effect on sugar content subsequently increased with the development of yellowing. Yellows reduced the water content, nitrogen content and the arealweight ratio of the leaf lamina. The change in nitrogen content, but not the others, could be accounted for by the rise in carbohydrate. Yellows had no effect on the water content of petiole and root; it increased the nitrogen content of these parts. It reduced the sucrose content of the root, but the loss of sugar yield was mainly attributable to decreased root weight. Infection with beet mosaic virus decreased the dry weight of sugar‐beet plants only when nitrogenous fertilizer was applied. As with yellows infection, the loss of dry matter resulted from reductions in both leaf area and N.A.R. Unlike yellows, mosaic depressed the dry weight of leaf lamina, as well as of petiole and root. Mosaic had no effect on carbohydrate content, water content or arealweight ratio of the leaf lamina, or on water content of petiole and root. It increased the nitrogen content of all parts of plants that received no nitrogenous fertilizer, but not of nitrogen‐treated plants. It slightly increased the sucrose content of the root. Infection with beet mosaic virus at the end of June caused a 20 yo loss of sugar yield from plants that received nitrogenous fertilizer. Yellows infection of similar plants at the same date reduced the sugar yield by 50%.

The Evaluation of Radiation Use Efficiency and Leaf Area Index Development for the Estimation of Biomass Accumulation in Short Rotation Poplar and Annual Field Crops

“…Besides LAI development in SRC poplar and AFCs, our LAD results were similar to previous studies where the LAD range varied between 58 and 180 days in AFCs (C 3 and C 4 crops) and SRC [28,47,68,71]. Higher LAI and LAD were achieved in SRC poplar as compared to AFCs because woody crops are taller, multi stemmed, and their developed roots systems may accommodate higher canopy closure as compared to AFCs [25,26,54].…”

“…Variations in the LAI max values are related to genotype, site (particularly soil conditions), length of the growing season, sowing density, and the availability of water and nutrients [27,68]. The LAI max may be strongly limited by reduced water availability resulting in reduced growth, yield, and yield components [69,70].…”

“…We observed fairly low RUE for OR (0.79 g MJ −1 ) and SM (1.19 g MJ −1 ) as compared to previous studies, where Kuai et al [67] and Williams et al [82] reported 1.07-1.09 g MJ −1 in OR and 1.71 g MJ −1 in maize, respectively. RUE values may be increased by favorable conditions such as higher water and nutrient (particularly N) availability [13,52,68,83]. RUE could also be affected by sowing density and genotype.…”

Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions

“…Plant yield is related to the photosynthetic intensity (Brantley & Young 2007) and assimilatory area, expressed as the leaf area index (LAI) (Watson 1947(Watson , 1952, which absorb solar energy in the range of photosynthetic active radiation PAR (400-700 nm). The absorbed PAR is converted into biochemical energy bonds which are used to reduce carbon dioxide to sugars (Blanko et al 2003, Norby et al 2003.…”

Physiology of Virus Diseases

“…The old idea that carbohydrate accumulated in the leaves because the phloem is blocked (102) seems no longer tenable, because leaves of sugar beet plants with yellows lose as much total carbohydrate when plants are in the dark as do uninfected plants (103) and leaf symptoms of potato leaf roll are not cor related with phloem necrosis (104). Infection with yellows virus does not affect leaf number and depresses the dry-matter yield of beet by decreasing both leaf area and net assimilation rate, the two effects being independent of one another (105). It increases the quantity of reducing sugars in the leaf greatly and gives smaller increases in sucrose and starch.…”