Aboveground production efficiency and canopy nutrient contents of mixed-hardwood forest communities along a moisture gradient in the central United States

1996 ◽  
Vol 26 (12) ◽  
pp. 2214-2223 ◽  
Author(s):  
Shibu Jose ◽  
Andrew R. Gillespie

The significance of canopy nutrients in regulating aboveground production efficiency of mixed-hardwood forest communities (ecological land type phases, ELTPs) was examined along a moisture gradient in southern Indiana, U.S.A. A total of 39 plots were established in six ELTPs in which canopy specific leaf area, canopy nutrient contents (N, P, K, Ca, and Mg on unit leaf area basis and on unit leaf weight basis), light transmittance, aboveground net primary productivity, and production efficiency (on unit leaf area basis, i.e., Earea; and on unit leaf weight basis, i.e., Emass) were quantified. ELTPs exhibited significant differences in canopy specific leaf area and aboveground net primary productivity. Although Earea varied significantly among ELTPs, Emass exhibited no significant differences. Variation in canopy specific leaf area was significantly correlated with ELTP site water balance (R2 = 0.93, p = 0.0083). Along a decreasing moisture gradient, canopy specific leaf area decreased, which resulted in an increase in canopy nutrient content per unit leaf area. Canopy nutrient contents (N, P, and K) in turn exhibited strong positive correlations with Earea (no strong correlations with Emass), which increased along a decreasing moisture gradient. Higher canopy nutrient contents coupled with higher light transmittance through the canopy probably results in a higher canopy photosynthetic efficiency (area basis) in dry ELTPs. This is suggested as one of the reasons for higher Earea in dry ELTPs than in mesic ELTPs.

1992 ◽  
Vol 19 (2) ◽  
pp. 171 ◽  
Author(s):  
FC Meinzer ◽  
NZ Saliendra ◽  
C Crisosto

Although carbon isotope discrimination (Δ) has been reported to decline in plants growing under reduced soil moisture, there is little information available concerning the dynamics of adjustments in Δ and gas exchange following a change in soil water availability. In this study Δ, photosynthetic gas exchange, and growth were monitored in container-grown coffee (Coffea arabica L.) plants for 120 days under three soil moisture regimes. At the end of 120 d, total leaf area of plants irrigated twice weekly was one half that of plants irrigated twice daily, although their assimilation rates on a unit leaf area basis were nearly equal throughout the experiment. This suggested that maintenance of nearly constant photosynthetic characteristics on a unit leaf area basis through maintenance of a smaller total leaf area may constitute a major mode of adjustment to reduced soil moisture availability in coffee. Intrinsic water-use efficiency (WUE) predicted from foliar Δ values was highest in plants irrigated weekly, intermediate in plants irrigated twice weekly and lowest in plants irrigated twice daily. When instantaneous WUE was estimated from independent measurements of total transpiration per plant and assimilation on a unit leaf area basis, the reverse ranking was obtained. The lack of correspondence between intrinsic and instantaneous WUE was attributed to adjustments in canopy morphology and leaf size in the plants grown under reduced water supply which enhanced transpiration relative to assimilation. Values of Δ predicted from the ratio of intercellular to ambient CO2 partial pressure determined during gas exchange measurements were not always consistent with measured foliar Δ. This may have resulted from a patchy distribution of stomatal apertures in plants irrigated weekly and from a lag period between adjustment in gas exchange and subsequent alteration in Δ of expanding leaves. The importance of considering temporal and spatial scales, and previous growth and environmental histories in comparing current single leaf gas exchange behaviour with foliar Δ values is discussed.


1982 ◽  
Vol 62 (1) ◽  
pp. 5-17 ◽  
Author(s):  
J. D. MAHON

Six genotypes of pea (Pisum sativum L.), selected for either high or low CO2 exchange rate per unit leaf area (CER) on the basis of field measurements, were grown in field plots during 1978 and 1979. During two growing seasons, CER was determined in leaves of different physiological age at several times of the day and season. Dry weights, leaf areas and node numbers were determined 4, 7 and 10 wk after planting, and again after pod ripening. C2H2 reduction by detached roots was measured 5, 6, 8 and 9 wk after planting. Despite the large variability in CER with years, leaf numbers, and times of measurement, the mean CER of the three genotypes selected for high rates was always greater than that of the low selected group. CER was significantly correlated with growth per unit leaf area (E) and the high to low group ratios averaged 1.4 for CER and 1.3 for E. C2H2 reduction on an equivalent leaf area basis was not different in the two groups. On a land area basis, the low CER group had a significantly greater leaf area index which compensated for the decreased CER, and estimates of total CO2 exchange, growth and C2H2 reduction were similar in the two groups. Total aboveground dry matter and seed yields were greater in the low CER group, but harvest index was generally greater in those genotypes selected for high CER.


1975 ◽  
Vol 23 (2) ◽  
pp. 253 ◽  
Author(s):  
HM Rawson ◽  
CL Craven

Changes in stomatal density and size were followed in tobacco and sunflower leaves expanding from 10% of final area (10% Amax) to Amax under different levels of radiation. Lower radiation increased final leaf area, reduced stomatal densities, and increased area per stoma but had little effect on stomatal area per unit leaf area at Amax. In very young leaves (20% Amax) there was a wide range in the sizes of individual stomata, some stomata being close to full size, but by Amax differences were small. The possible relationship between the developmental patterns described and photosynthesis is briefly discussed.


Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 534-540 ◽  
Author(s):  
Ronald E. Jones ◽  
Robert H. Walker

Greenhouse and growth chamber experiments with potted plants were conducted to determine the effects of interspecific root and canopy interference, light intensity, and soil moisture on water uptake and biomass of soybean, common cocklebur, and sicklepod. Canopy interference and canopy plus root interference of soybean with common cocklebur increased soybean water uptake per plant and per unit leaf area. Root interference with soybean decreased common cocklebur water uptake per plant. Canopy interference of soybean with sicklepod increased soybean water uptake per unit leaf area, while root interference decreased uptake per plant. Combined root and canopy interference with soybean decreased water uptake per plant for sicklepod. Soybean leaf area and shoot weight were reduced by root interference with both weeds. Common cocklebur and sicklepod leaf area and shoot weight were reduced by root and canopy interference with soybeans. Only common cocklebur root weight decreased when canopies interfered and roots did not. The relationship between light intensity and water uptake per unit leaf area was linear in both years with water uptake proportional to light intensity. In 1991 water uptake response to tight was greater for common cocklebur than for sicklepod. The relationship between soil moisture level and water uptake was logarithmic. Common cocklebur water uptake was two times that of soybean or sicklepod at −2 kPa of pressure potential. In 1991 common cocklebur water uptake decreased at a greater rate than soybean or sicklepod in response to pressure potential changes from −2 to −100 kPa.


1988 ◽  
Vol 15 (2) ◽  
pp. 107 ◽  
Author(s):  
WS Chow ◽  
L Qian ◽  
DJ Goodchild ◽  
JM Anderson

The photosynthetic acclimation of Alocasia macrorrhiza (L.) G. Don, a species naturally occurring in deep shade in rainforests, has been studied in relation to a wide range of controlled irradiances during growth (~3-780 �mol photons m-2 s-1 of fluorescent or incandescent light, 10 h light/ 14 h dark). At the maximum growth irradiances, the light- and CO2-saturated rates of O2 evolution per unit leaf area were ~4 times as high as at low irradiance, and approached those of glasshouse-grown spinach. Growth at maximum irradiances reduced the quantum yield of O2 evolution only slightly. Changes in the anatomy of leaf tissue, the ultrastructure of chloroplasts and the composition of chloroplast components accompanied the changes in photosynthetic functional characteristics. At low growth irradiance, palisade cell chloroplasts were preferentially located adjacent to the distal periclinal cell walls and had large granal stacks, and the destacked thylakoids had a very low surface charge density. In contrast, at higher growth irradiance, palisade cell chloroplasts were preferentially located adjacent to the anticlinal cell walls; they had small granal stacks, large stromal space, and a high surface charge density on the destacked thylakoids. The number of chloroplasts per unit section length increased with growth irradiance. Ribulosebisphosphate carboxylase activity per unit leaf area increased markedly with irradiance. Photosystem II, cytochrome f and latent ATPase activity per unit chlorophyll increased to a lesser extent. While the chlorophyll a/chlorophyll b ratio increased substantially with growth irradiance, the chlorophyll content per unit leaf area declined slightly. Our results show that coordinated changes in the structure of leaf tissue, and the organisation and composition of chloroplast components are responsible for Alocasia being capable of acclimation to high as well as low irradiance.


1985 ◽  
Vol 63 (4) ◽  
pp. 716-721 ◽  
Author(s):  
Marianna Krol ◽  
Norman P. A. Huner

Accumulation of chlorophyll, the carotenoids (β-carotene, lutein, violaxanthin, and neoxanthin), and the benzoquinones (plastoquinone A and α-tocopherol) were monitored in 'Puma' rye as a function of leaf ontogeny at warm and cold-hardening temperatures. Although the kinetics of accumulation differed among the leaves of warm-grown plants, the initial and maximum levels of the pigments and benzoquinones expressed on a leaf area basis did not differ significantly among the first four leaves of the main culm. In contrast, the third and fourth leaf of cold-grown plants, which developed completely at the low temperature, generally exhibited initial and maximum pigment and benzoquinone levels 60–300% greater than was observed for leaf 1 and 2 of cold-grown plants, which were completely or partially developed at the warm temperature regime. This resulted in pigment and benzoquinone levels which were 1.6- to 3-fold greater in the plants grown at cold-hardening temperatures than those grown at the warm temperature, when expressed on a per unit leaf area basis. However, when pigment accumulation was calculated on a chlorophyll basis, the benzoquinone content of leaves that developed solely at cold-hardening temperatures exhibited a 1.7-fold increase over the same leaves developed at warm temperatures. Carotenoids did not exhibit this trend. Calculations based on chlorophyll/carotenoid content and dry weight accumulation indicated that leaves that were developed at cold-hardening temperatures appeared to produce more dry matter per unit of photosynthetic pigments than the same leaves that were developed at nonhardening temperatures.


HortScience ◽  
2016 ◽  
Vol 51 (7) ◽  
pp. 843-846 ◽  
Author(s):  
Toshio Shibuya ◽  
Ryosuke Endo ◽  
Yoshiaki Kitaya ◽  
Saki Hayashi

Light with a higher red to far-red ratio (R:FR) than sunlight reduces plant growth, but the cause has not been firmly established. In the present study, cucumber seedlings were grown under normal light (similar to sunlight; R:FR = 1.4) from metal-halide lamps or high-R:FR light (R:FR = 4.3) created by transmitting their light through FR-absorbing film, and then their growth parameters and photosynthesis were compared. The relative growth rate (RGR) at high R:FR was 92% of that under normal R:FR, although the net assimilation rate (NAR) did not differ between the treatments, indicating that changes in net photosynthesis per unit leaf area did not cause the growth inhibition at high R:FR. The CO2 exchange per unit leaf area did not differ between the treatments, which supports this hypothesis. The leaf area ratio (LAR) of total plant dry weight of high R:FR seedlings to that of normal R:FR seedlings was also 92%. This suggests that growth suppression in the high R:FR seedlings was caused mainly by decreased LAR. The specific leaf area (SLA) and leaf weight ratio (LWR), components of LAR, under high-R:FR light were 89% and 105%, respectively, of those under normal light, indicating that the smaller LAR at high R:FR mainly results from suppressed leaf enlargement per unit leaf dry matter.


2016 ◽  
Vol 42 (3) ◽  
Author(s):  
Alessio Fini ◽  
Ciro Degl’Innocenti ◽  
Francesco Ferrini

The effects of mixed compost as mulching material on growth and physiology of newly planted elm trees were evaluated over a three-year period after planting in an urban park. Trees mulched with compost generally had greater height (+10% and +19% for 5 cm layer and 10 cm layer treatments, respectively, if compared to control), trunk diameter (+13% and +29%) and current-year shoot growth (+46% and +56%). Limited effects were found with regard to carbon assimilation when considered on a per unit-leaf-area basis (-0.1% and +0.3%), but whole tree carbon assimilation increased in mulched trees (+7% and +59% for 5 cm and 10 cm treatments, respectively, if compared to control) because of the larger total tree leaf area of mulched plants. Mulching also increased chlorophyll content (+4% and +7% for 5 cm and 10 cm treatments, respectively). The results obtained in this study show how mulching with compost increased growth, carbon storage, and improved water use efficiency of trees planted in an urban environment characterized by hot dry summers.


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