on-farm experiments were designed to investigate the response of maize establishment and grain yield to variation in tillage systems. the tillage treatments included arara ploughing followed by zig-zag harrowing and arara ridging (t1); emcot ploughing fol-lowed by zig-zag harrowing and emcot ridging (t2); mouldboard ploughing followed by disc harrowing and mouldboard ridging (t3); disc ploughin...

two field and laboratory experiments were conducted to investigate the effects of superabsorbent polymer (sap) and irrigation management on seed and essential oil yields of cumin, as well as the impact of water quality on water holding capacity of sap. salinity had a negative effect on the amount of water absorbed by sap (335 and 59 g h2o per g sap, for distilled water and solution of 0.5% nacl...

Recent studies have shown that stomata respond to changes in hydraulic conductance of the flow path from soil to leaf. In open-grown tall trees, branches of different heights may have different hydraulic conductances because of differences in path length and growth. We determined if leaf gas exchange, branch sap flux, leaf specific hydraulic conductance, foliar carbon isotope composition (delta...

Coniferous tree canopies typically carry more leaf area than is necessary to intercept most of the incoming light. I postulated that an excessively large leaf area will reduce net productivity at tree level, unless the net photosynthetic production of the most shaded shoots in the canopy remains positive. The hypothesis tested was that a coniferous tree canopy maintains a large productive leaf ...

Leaf inclination angle distribution is an important canopy structure characteristic which directly impacts the fraction of the intercepted solar radiation. Together with the leaf area index (LAI) it determines the structure and fractional cover of a homogeneous crop canopy. Unfortunately, this key canopy parameter has usually been ignored when applying common multispectral vegetation indices to...

BACKGROUND AND AIMS Plant architecture and its interaction with agronomic practices and environmental constraints are determinants of the structure of the canopy, which is involved in carbon acquisition and fruit quality development. A framework for the quantitative analysis of grapevine (Vitis vinifera) shoot architecture, based on a set of topological and geometrical parameters, was developed...

Relative absorptance of intact branches measured with an integrating sphere was compared to leaf area estimated by conventional methods (volume displacement and scanning area meter) for three conifer species: Picea mariana (Mill.) BSP, Pinus banksiana (Lamb.) and Pseudotsuga menziesii (Mirb.) Franco. A consistent relationship between relative absorptance and surface area emerged for the three s...

BACKGROUND AND AIMS It is well known that plant aerial development is affected by light intensity in terms of the date of flowering, the length of stems and petioles, and the final individual leaf area. The aim of the work presented here was to analyse how shade-induced changes in leaf development occur on a dynamic basis from the whole rosette level to that of the cells. METHODS Care was tak...

Detailed one-dimensional multilayer biosphereatmosphere models, also referred to as CANVEG models, are used for more than a decade to describe coupled watercarbon exchange between the terrestrial vegetation and the lower atmosphere. Within the present study, a modified CANVEG scheme is described. A generic parameterization and characterization of biophysical properties of Amazon rain forest can...

Leaf area and its spatial distribution are key canopy parameters needed to model the radiation regime within a forest and to compute the mass and energy exchange between a forest and the atmosphere. A much larger proportion of available net radiation is received at the forest floor in open-canopy forests than in closed-canopy forests. The proportion of ecosystem water vapor exchange (lambda E) ...