Reduction In Total Leaf Area Research Articles

Evaluation of the hydraulic press for measurement of leaf water potentials in cassava

SUMMARYIn the application of the Scholander pressure chamber technique to cassava water relations studies, the leaf water potential measured on central lobules was initially compared with that measured on entire leaves (including petiole). Measurements made using both a Campbell-Brewster hydraulic press and a pressure chamber of the leaf water potential in six different cassava clones were also compared. Although the central lobules showed a greater sensitivity to moisture loss after sampling than entire leaves, their leaf water potential was in close agreement with those measured on the entire leaves (r3 = 0·96). Therefore, for routine and field estimates in cassava, measurements made on the central lobules may be used to avoid the large reduction in total leaf area. The Campbell-Brewster hydraulic press satisfactorily estimated leaf water potential in M.Col. 1684 clone, which had the longest and narrowest lobules, but in other clones the leaf water potential was overestimated at high leaf potential (> -12·5) and underestimated at low water potentials (< -12·5). Over a wide range of leaf water potentials, a poor relationship between leaf water potentials estimated with hydraulic press and with the pressure chamber was observed for cassava because press estimates are influenced by lobule length and lobule width.

Influence of spectral quality on the growth response of intact bean plants to brassinosteroid, a growth‐promoting steroidal lactone. II. Chlorophyll content and partitioning of assimilate

The chlorophyll content and partitioning of assimilate of bean (Phaseolus vulgaris L. ‘Pinto′) plants were determined 6 days after treatment of the second internode (I2 with 5 μg of brassinosteroid (BR), a growth‐promoting steroidal lactone. Plants were grown for 6 days under equal levels (90 μmol s‐1 m‐2) of photosynthetic photon flux density (PPFD) provided by cool white fluorescent (CWF) or incandescent (INC) lamps and equal levels of far‐red (28 W m‐2, 700–800 nm) radiation provided by the same INC or far‐red (FR) fluorescent lamps. Brassinosteroid treatment had no appreciable effect on total biomass production but caused a decrease of 15–20% dry matter distribution in the upper portion of the shoot, a small (4%) but constant increase in dry matter in l2 and a large (11–16%) increase in dry matter in the lower portion of the shoot (especially I1). Treatment with BR increased assimilate accumulation in the primary leaves, especially under INC and FR lamps, and reduced dry matter in the trifoliate leaves. BR also caused a 16–21% reduction in total leaf area and even a greater reduction in area of the trifoliate leaves, but significantly increased specific leaf weight of the primary leaves and the first trifoliate leaf and the amount of dry matter in the lateral shoots under all radiation sources. In comparison to controls, BR treatment increased dry matter accumulation in the treated internode 3.3x under CWF and 1.6x under INC or FR. BR treatment also increased chlorophyll content in the primary leaves under all radiation sources and in the trifoliate leaves under CWF and INC lamps. These findings suggest a possible mobilization role of BR and establish the importance of adequate PPFD (and photosynthate) for maximum swelling and splitting response to brassinosteroid.

Influence of Alfalfa Bud Mite on Growth of Alfalfa under Different Temperatures1

The influence of four temperatures (15, 20, 25, and 29 C) on the growth of alfalfa (Medicago sativa L) seedlings, initially infested with 10 alfalfa bud mites (Eriophyes medicaginis Keifer) per seedling, was studied.Mite infestation caused significant reductions in dry weight of leaves and stems, petiole length, and leaf area of the seedlings at all temperatures. Dry weight reductions of infested seedlings were greatest at 25 and 29 C. The greatest reductions in stem and petiole length and leaf area occurred at 29 C. The reduction in total leaf area per plant due to mite infestation was similar at 15, 25 and 29 C but there was less reduction at 20 C.The influence of bud mite infestation on the growth of alfalfa seedlings appears to be expressed mainly as a reduction of extension growth. This results in reduced leaf expansion and reduced elongation of the stem and petiole.

Leaf Area Consumption of Cotton, Peanuts, and Soybeans by Adult Graphognathus peregrinus and G. leucoloma1

In laboratory tests, leaf area consumed by adult Graphognathus peregrinus (Buchanan) averaged 0.30, 0.72, and 0.92 cm2/day for cotton, peanut, and soybean foliage, respectively. Graphognathus leucoloma (Boheman) consumed 1.40 and 2.17 cm2/day of peanut and soybean foliage, respectively. In field cage tests, populations of 50 or more G. leucoloma /plant caused a significant reduction in total leaf area of R3 soybeans and reduced total pod production. Populations of 10 G. peregrinus /V5 soybean plant caused a significant reduction in total leaf area but did not significantly reduce yield.

Leaf Area Indices and Nitrogen Uptake of Flue‐Cured Tobacco as Affected by Plant Density and Nitrogen Rate1

AbstractEffects of three plant densities and two nitrogen rates on leaf areas and nitrogen uptake by tobacco plants were studied during 1961 and 1962. A study was also made on the economics of these treatments.Leaf area indices (LAI's) for both years increased with time until the reduction in total leaf area through loss of senescent lower leaves became greater than the gain in leaf area of the active upper leaves. The highest maximum LAI of 5 in 1961 was obtained for the high nitrogen rate and the 25‐cm spacing. The lowest maximum LAI of 2.5 was obtained for the low nitrogen rate and the 76‐cm spacing. LAI's increased with high nitrogen and at both levels of nitrogen the LAI's were in the order of 25 > 51 > 76‐cm spacings in 122‐cm beds.Relationships between leaf area and leaf weight per plant were very similar during 1961 and 1962. Correlation coefficients for leaf areas and weights varied from 0.95 to 0.99 in 1961 and from 0.92 to 0.99 in 1962. In both years, better correlation appeared between leaf areas and weights at the high nitrogen rate than at the low nitrogen rate, with spacing treatments having little effect on the relationships.Nitrogen uptake was much higher with the high nitrogen treatment than with the low nitrogen treatment.The yield of flue‐cured tobacco increased with closer plant spacing and the higher nitrogen rate. However, leaf quality decreased with the high nitrogen rate and offset the higher yields in total dollar value per hectare. The quality of tobacco appeared to be influenced more by the nitrogen application than by the different plant spacings~ The most profitable treatment combination appeared to be the 76‐cm spacing at the low nitrogen rate.

Studies on the Photosynthesis of Sugar Beet Plants : (1) Changes in the photosynthetic ability under field condition

Experiments were carried out to investigate the photosynthetic activities of sugar beet plants. The results obtained are as follows: Each leaf of sugar beet plants had its own activity and the youngest matured leaf showed the highest activity. Photosynthetic amount per plant growing in the sugar beet plant community increased with enlargement of total leaf area but the amount did not increase at the same rate of enlargement of leaf area, then the ability decreased with reduction of total leaf area at maturing stage. Photosynthetic amount per 100 cm2 (leaf area) became lower in proportion to enlargement of total leaf area and showed the lowest amount at the maximum leaf area. Consequently it may be concluded that the leaves were shaded with each other and the light receiving coefficient became lower at the most flourishing stage.