Canopy Light Distribution Research Articles

Shade nets effect on canopy light distribution and quality of fruit and spur leaf on apple cv. Fuji

The upper region of the Río Negro and Neuquén valley, Argentina (latitude: 38 degrees 55 minutes South) experiences high temperatures and light intensities before the apple harvest. This hinders these fruits turning red and increases the risks of them becoming sunburnt. In the December of two growing seasons (when the fruits were about 43 mm in diameter), still some 80 days before harvest, 15% and 55% density shade nets were placed over "Fuji" apple trees. At harvest time, light distribution was determined at two canopy heights (1 and 3 m) on either side of the trees. Fruiting spurs were examined, and colour, sunburn damage, weight, soluble solid content and flesh firmness of the fruits determined. Specific leaf weight (SLW) was also established. Shade nets notably decreased the amount of photosynthetically active radiation (PAR) available; they also reduced fruit colour (redness), soluble solid content and flesh firmness, and the SLW. The 55% density net decreased fruit sunburn, but no differences were found between the 15% density net and control treatments. Spurs at the bottom of the canopy received less light, and the SLW, as well as the colour and soluble solid content of their fruit, was lower than observed for the higher spurs. The impossibility of exporting fruits damaged by high temperatures and intense solar radiation during ripening requires shade nets be used, their density depending on the conditions experienced.

Seasonal Variations in Light and Leaf Nitrogen Distribution in a Cryptomeria japonica Canopy.

Seasonal Variations in Light and Leaf Nitrogen Distribution in a Cryptomeria japonica Canopy.

Modeling the light interception and carbon gain of individual fluttering aspen (Populus tremuloides Michx) leaves

Poplars (Populus spp.) have a particular petiole morphology that enhances leaf flutter even in light winds. Previous studies have shown that this trait enhances whole canopy carbon gain through changes in the temporal dynamics and spatial distribution of light in the lower canopy. However, less is known about the effects of flutter for leaves at the top of the canopy ("sun leaves"). A computer simulation model was developed that uses latitude, time of day, day of year, azimuth and a slope component, which was varied at a 3 Hz frequency over an arc of rotation to create the flutter motion, and generate data on light interception for both surfaces of a fixed or fluttering leaf. The light files generated (10 Hz) were input into a dynamic model of photosynthesis to estimate the carbon gain for both fluttering and fixed leaves. As compared to leaves fixed at various angles and azimuths, fluttering leaves had a more uniform light interception. Depending on their angle and azimuth, fixed leaves may not always be intercepting high photon flux density (PFD) even when exposed to full sun. Leaf flutter continuously randomizes leaf angles creating uniform PFD inputs for photosynthetic reactions regardless of variation in leaf orientation and solar position. These effects on light interception could have positive impacts on carbon gain for leaves at the top of the canopy.

‘Daleks’ and ‘Whirligig’ used to uncover the fate of intercepted light by an apple tree canopy

Canopy light interception and distribution has a major influence on CO2 fixation and the growth and productivity of fruit trees. Spatial and temporal variations in microclimate alter the gas exchange from the leaves and other organs (fruit, branch, etc.). The variable nature of the light environment within the tree crown, and other factors such as leaf age and various stresses (water, diseases, pests) can often impair our ability to extrapolate whole-canopy net carbon exchange (NCE) and transpiration from a small sample of single-leaf measurements. This paper compares two methods for estimating whole-canopy gas exchange. An open-top, through-flow whole-canopy cuvette (Wunsche & Palmer, 1997, HortScience, 32:653-658) was used to enclose the above-ground portion of a 4 year-old apple tree (Malus domestica Borkh. cv. `Braeburn? on M.9 rootstock). NCE and transpiration from the whole canopy was measured over a one week period in mid-season. Measurements of light interception were made on a neighbouring apple tree of the same age and of a similar growth habit using a `whole-plant? radiometer known as the Whirligig (McNaughton et al., 1992, Plant Cell Environ., 17:1061-1068). Data from the Whirligig were used to estimate the distribution of PAR radiation over the total leaf area of the tree. This PAR distribution was then combined with leaf stomatal conductance and leaf net photosynthesis response functions to estimate the rates of whole-canopy NCE and transpiration. The Whirligig calculations of transpiration were in good agreement with data from the whole-canopy cuvette, and with independent measurements of sap flow recorded using heat-pulse sensors located in the trunk of the cuvette tree. The Whirligig estimates of NCE were also comparable to values obtained from the whole-canopy curvette. We conclude that both instruments provide an integrated approach for whole-plant productivity studies

Nitrogen Shortage in a Tomato Crop; Scaling up from Effects on Electron-Transport Rate to Plant Productivity

Optimization of nitrogen supply in a tomato plant is stepwise assessed, from chloroplast characteristics to whole crop performance. Experiments are reported in which important key processes are quantified in relation to the nitrogen content of leaves. Interactions of N effects with leaf aging and canopy light distribution are analyzed. A simulation model that integrates this knowledge is constructed. The results of three nitrogen partitioning scenarios for Rubisco suggest that optimization of the distribution of Rubisco between leaf layers is less important for plant productivity than within-leaf optimization of the photosynthetic apparatus

Light distribution and foliage structure in an oak canopy

Leaf angle distribution and shoot bifurcation ratio were measured and related to photon flux density (PFD) distribution in an oak canopy. Leaf angle distribution deviated substantially from random and changed markedly throughout the canopy. The observed leaf angle distribution was described by an ellipsoidal function with the single parameter of the distribution, x, changing from 1.6 at the top of the canopy to 3.2 in the lowest branches. In vertically homogeneous canopies, the extinction coefficient for diffuse radiation is expected to decline with increasing leaf area index (LAI). However, in the canopy studied here, the leaf angle distribution changed with height such that the effective extinction coefficient remained constant. Both shoot bifurcation ratio and leaf number per shoot declined with decreasing PFD inside the canopy. Based on these observed relationships, a simple canopy growth model that assumes horizontal homogeneity of the canopy was constructed. Calculations showed that a steady state, when growth in the upper of the canopy is in equilibrium with decline of lower canopy, the total canopy LAI should equal to 4.3. This predicted value of equilibrium LAI is larger than that estimated from measurements of PFD transmission (LAI=3.3), but smaller than that directly determined by litter collection (LAI=6.2 in 1998). Possible reasons for these discrepancies are discussed.

Hazelnut Production in Oregon

Hazelnuts in Oregon are grown on 30,000 acres by ≈1000 orchardists in the Willamette Valley. Their annual production accounts for 3% to 5% of the world's hazelnut tonnage. The trees are grown in a single trunk system wrtb an average spacing of 20 feet between trees. Mechanical harvestihg is done in October. The industry employs an Integrated Pest Management approach, utilizing combinations of scouting, trapping, and biological control. The main insect pests are filbertworm, filbert leafroller, obliquebanded leafroller, and filbert aphids. The aphid parasite Trioxys pallidus was imported from Europe and successfully established in Oregon. Eastern Filbert Blight, Anisogramma anomala, a fungus disease, is the most serious disease problem in the industry. Annual applications of nitrogen to the soil and boron applied to the foliage are routine for Oregon's hazelnut growers. OSU research has quantified the importance of good light distribution in the tree canopy for increased nut production. OSU recommends a 5-year rotational pruning program. Some growers use mechanical hedging instead of hand pruning. OSU is home to the world's largest hazelnut breeding program. `Barcelona' is still the main, cultivar grown, while `Ennis' is the main in-shell variety. There is growing interest in planting varieties with a high percent kernel, such as `Casina', `Willamette', and `Lewis'.

Canopy Light Distribution, Photosynthesis and Tuber Yield of Eddoe Plant Characterized by Clipping and Non-Clipping of Daughter Tuber Leaves

The effects of clipping of daughter tuber leaves of eddoe plants (Colocasia esculenta Schott, var. antiquorum Hubbard, cv. Uhan) on dry matter production, canopy photosynthesis and tuber yield were investigated. The clipping of daughter tuber leaves resulted in different vertical canopy structure and different light distribution within the canopy. In the row-base of the non-clipped plot, relative light intensity was 10% lower than in the clipped plot. In the non-clipped plot, net photosynthetic rate of eddoe plant reached 4.9g CO2 m-2 h-1, while in the clipped plot, it reached only 2.7g CO2 m-2 h-1. The non-clipped plot attained a total tuber yield of 1844g m-2 but the clipped plot reduced tuber yield approximately by 25%. We presume that the canopy of the non-clipped plot intercepted more light due to higher LAI (leaf area index) than the clipped plants. The higher LAI and higher light interception of non-clipped plants resulted in higher photosynthesis and higher dry matter production and hence higher tuber yield than in the clipped plot.The present experiment concluded that daughter tuber leaves have a great contribution to the canopy photosynthesis and to promoting thickening growth of tuber. Therefore, it would be better not to clip daughter tuber leaves for obtaining higher tuber yield.

Dependence of canopy light distribution on leaf and canopy structure for two cotton ( Gossypium) species

The light environment within a crop canopy is an important determinant of the potential photosynthetic activity of the crop. The photon flux environment within the crop is influenced by the total incoming radiation and the structure of the plant canopy. In this study, the light environment within two economically important species of cotton ( Gossypium, sps.) that show diverse growth habits was examined at different growth stages. G. hirsutum had very regular leaf shapes throughout the growing season, and was diaheliotropic. G. barbadense had large, fairly flat leaves early in the season that progressively became more cupped at increasing mainstem positions, and had no heliotropic response. These differences in leaf shapes and solar tracking altered the leaf and canopy light environment. Estimated total diurnal light intercepted by upper canopy leaves was found to be lower for G. barbadense than for G. hirsutum, due in part to the cupping of the leaf surface. Alternatively, the cupping of the G. barbadense leaves resulted in a more erectophile canopy, increasing PFD to lower canopy leaves in the G. barbadense canopy particularly later in the season relative to that PFD observed in the G. hirsutum canopy. This redistribution of light to lower canopy leaves has been suggested to be beneficial by increasing net canopy photosynthesis. The cupping of the G. barbadense leaves, in addition to distributing light over a greater photosynthetically active area, may be beneficial by reducing photoinhibition. Additionally, the extreme cupping of the G. barbadense leaves results in illumination of the abaxial surface during portions of the day, which may further increase the photosynthetically active area and contribute to total canopy carbon uptake.

Leaf Position, Light Levels, and Nitrogen Allocation in Five Species of Rain Forest Pioneer Trees

We used path analysis to ask whether leaf position or leaf light level was a better predictor of within-plant variation in leaf nitrogen concentration in five species of rain forest pioneer trees (Cecropia obtusifolia, Ficus insipida, Heliocarpus appendiculatus, Piper auritum, and Urera caracasana) from the Los Tuxtlas Biological Station, Veracruz, Mexico. Three hundred seventy-five leaves on 28 plants of the five species were analyzed for leaf nitrogen concentration, leaf mass per area, and leaf light interception at different positions (= nodes) along a shoot. Mean values of leaf nitrogen concentration ranged from 0.697 to 0.993 g/m2 in the five species, and varied by as much as 2.24 g/m2 among leaves on individual plants. Leaf position on the shoot explained significantly more of the within-plant variation in leaf nitrogen concentration than did leaf light level in four of the five species: Cecropia obtusifolia, Heliocarpus appendiculatus, Piper auritum (branch leaves only), and Urera caracasana. However, individual species differed considerably in the patterns of nitrogen allocation and leaf mass per area among leaves on a shoot. These results suggest that leaf nitrogen deployment in these plants is, in part, developmentally constrained and related to the predictability of canopy light distribution associated with plant growth form.

Effects of Canopy Light Distribution Characteristics and Leaf Nitrogen Content on Efficiency of Radiation Use in Dry Matter Accumulation of Soybean Cultivars.

ダイズ品種の乾物生産力を, 個体群の補捉日射エネルギー(PAR)当たりの乾物生産量(EPAR)で評価し, それに関連する要因を解析した. 1989年にダイズ11品種を, 1990年に27品種を滋賀県立短期大学農業部畑圃場で栽培した. 個体群補捉日射量の推移, 地上部全乾物重の推移, 群落吸光係数(KPAR), 葉面積当たり窒素濃度(SLN)および地上部全窒素含量(1990年のみ)を測定した. EPARの全品種平均値は両年とも2.48gMJ-1であった. 変動係数でみると品種間には±9%(1989年)あるいは±17%(1990年)の変異がみられ, 全体に新しい品種が旧品種よりも勝っていた. EPARはSLNとの間に正の相関関係を示した(1989年r=0.548, 1990年r=0.651)が, KPARとの間には相関関係がみられなかった. SLNが比葉重(SLW)と密接な関係(1989年r=0.954, 1990年r=0.710)を示したことから, EPARにみられる新旧品種間差異は, 主として葉身の形態特性の改善による個葉光合成能力の増大によるものと推察された. SLNはさらに, 地上部全窒素含量と正の相関を示し(1990年, r=0.736), 個体全体の窒素蓄積量の制限を受けるようであった.

EFFECT OF DORMANT PRUNING REGIMES ON CANOPY LIGHT DISTRIBUTION, FRUIT AND SPUR QUALITY, AND FRUIT PACKOUT OF `MCINTOSH' APPLES.

A randomized complete block study was initiated in 1991 in a fifteen year old `Rogers Red McIntosh'/9-106 interstem orchard to investigate the effect of three dormant pruning regimes- an unpruned control, selectively thinned, and heavily structured or “tiered”, on tree canopy light distribution and fruit and spur quality. Fruit quality parameters being measured for the 1991 and 1992 harvests include skin color (% red blush), weight (g.), flesh firmness (kg.), soluble solids concentration (% Brix), and packout (% fancy grade). Pruning treatment effect on fruit spur quality, in terms of spur bud diameter (mm.) and spur efficiency (leaf dry weight/spur), is also being evaluated at time of harvest. Light distribution is being measured (% PAR, umol/s/m2.) within the tree canopy from petal fall through harvest. Preliminary findings indicate there is a difference in tree canopy light distribution and some fruit quality measurements, including red skin color, between pruning regimes. Complete analysis of results from 1991 will be presented.

The effects of row orientation, tree height, time of year and latitude on light interception and distribution in model apple hedgerow canopies

SummaryA computer model was used to calculate light interception and distribution within apple hedgerow canopies at different times of the year, at row spacings of 2, 3 and 4 m, at latitudes of 51.3, 40 and 30°N, for tree heights from 0.5–4 m, with row orientation N–S or E–W and at constant leaf area density. The effect of row orientation was complex and depended on the other factors. In mid-summer, N–S rows intercepted more light than E–W rows with larger differences at lower latitudes and at the wider spacings. At the equinox, E–W rows intercepted more light than N–S rows at higher latitudes Iput there was little difference at 30°N. Light interception was not affected by row orientation when hedge height was less than 1 m, or at 2 m row spacing on days with low solar altitudes. Light distribution was improved with wider spacings in N–S rows, but this was only the case for E–W rows when solar altitudes were low. Light distribution was better in N–S rows in mid-summer at the time of floral initiation but this was reversed at 51.3°N at the equinoxes.

Light interception and distribution in horizontal and vertical canopies of red raspberries

SummaryLight interception by several plantations of horizontally (New Zealand canopy) and vertically trained red raspberries was recorded at the start of flowering and at harvest. The maximum daily light interception was 81% of incident light, achieved by a vertical system in rows 2.5 m apart. Measurements of light distribution within the canopy showed improved light penetration with the horizontal compared to the vertical training. Calculated values of light interception from a computer model showed close agreement with measured values. Using published data on the effect of between-row spacing on yield, yield was found to be a function of light interception, calculated from the model. The model was then used to define the row spacing of the horizontal canopy system which would attain equivalent levels of light interception to those of the vertical system. Results of a small shading trial indicated that the cropping of the horizontal canopy was unlikely to suffer from the shade cast by the vegetative cane...

DRY MATTER ACCUMULATION OF MAIZE GROWN HYDROPONICALLY UNDER CONTROLLED-ENVIRONMENT AND FIELD CONDITIONS

The early-maturing maize (Zea mays L.) hybrid Pioneer 3978 was grown hydroponically in controlled-environment growth rooms during a 4-yr period. Plant dry matter accumulation and distribution were measured from 15 days before silking until date of black layer formation. Light distribution in the maize canopy and leaf carbon exchange rates at various positions in the canopy were measured and leaf area index and leaf area distribution were calculated, in order to compare crop growth rates with estimated rates of crop dry matter accumulation. In addition, Pioneer 3978 and two late-maturing maize hybrids, DeKalb XL55 and DeKalb XL72AA were grown in the field using the same hydroponic system employed in the growth rooms. Dry matter accumulation, dry matter distribution and grain yield were measured for the field-grown maize. Average crop growth rate for maize grown in the growth rooms from 15 days before to 15 days after silking was in excess of 40 g∙m−2∙day−1, with an efficiency of conversion of photosynthetic-active radiant energy into plant dry matter of 12.9%. Rate of dry matter accumulation declined to approximately 20 g∙m−2∙day−1 during the period from 15 days after silking to date of black layer formation. Average final dry matter and grain yield for the 4-yr experiment were 26.0 and 11.5 tonnes/ha, respectively. Estimated rates of dry matter accumulation by the maize canopy as calculated from photosynthesis-irradiance response curves, leaf area and measurements of light distribution appeared to indicate a substantial increase in nonfoliar respiration during the period of rapid dry matter accumulation of the grain. The hydroponic system, consisting of "Turface" — supporting medium and nutrient solution, did appear to enhance rate of dry matter accumulation. Maximum crop growth rates of hydroponically grown maize in the field were 52–2 g∙m−2∙day−1, which is more than 50% higher than maximum crop growth rates of field-grown maize at Guelph. Results of these experiments indicate that the inherent yield potential of maize is much higher than yields obtained under normal field conditions.Key words: Zea mays L., crop growth rate, dry matter distribution, photosynthetic efficiency, yield potential, carbon exchange rate

Light Distribution in Discontinuous Canopies: Calculation of Leaf Areas and Canopy Volumes Above Defined ‘Irradiance Contours’ for use in Productivity Modelling

Light Distribution in Discontinuous Canopies: Calculation of Leaf Areas and Canopy Volumes Above Defined ‘Irradiance Contours’ for use in Productivity Modelling

Growth of Birdsfoot and Alfalfa. III Changes in Carbohydrates Reserves and Growth Analysis Under Field Conditions1

The amount of total available carbohydrates (TAC) in the roots of 'Empire' birdsfoot trefoil were lower and the changes were less pronounced than in the roots of 'Vernal' alfalfa at similar growth stages. The difference on a weight basis was much greater than by percentage. Starch, sucrose, glucose, and fructose were the components of the TAC of both species. Relationships among the fractions of the TAC were similar for both species throughout the growing season.Alfalfa had a higher crop growth rate (CGR) than trefoil except at late stages of maturity when growth of trefoil continued by active upper axillary branching. CGR of alfalfa was higher than trefoil because there was a greater leaf area and it developed faster. Alfalfa was more efficient in the conversion of radiant energy into dry matter because it had a higher leaf area index than trefoil at comparable net assimilation rates. This advantage over trefoil was attributed to a higher photosynthetic rate for alfalfa leaves and to a better light distribution in the taller alfalfa canopy.