oco chodzi z tymi lisciami wiatrakowymi , moglby ktos wyjasnic? dzieki<wodna>
KNNA napisał:Zamieszczone przez knna
Thanks, guys. I hope we can work improving our setups by eliminating the wrong concepts that lead us to work on wrong directions.
In this sense, lets examine Penetration (BTW, if you want to find thousands of excelent botanists articles about this topic, search for "extinction coefficient k" (add "canopy" to eliminate results of other areas apart of botany).
The main thing I would like to dispell about Penetration is that the light source caracteristics, although affect on some degree, dont rule out it, but is one of the factors that affect less penetration. At least, if we consider just top lighting.
Penetration is mainly ruled out by how crowded is the grow area (how many leaves) and the angle of leaves. Light density achieved at bottom areas mainly depends of them, and just minimally of the caracteristics of the lighting, especially if its a fixed one.
Some botanist concepts are usefull in this context. Leaf Area Index (LAI) is an adimensional figure that informs of how many leaves there are for surface unit area. It sums the area of upper part of all leaves and divide it by the surface area of the grow. Thus a LAI=1 means that on a 1 sq meter of grow area, there is 1 sq meter of leaves (counting only upper part).
In general LAI is over 1, mostly between 2-4, but it may reach 6. Notice that growing techniques often are intended to strongly affect this parameter, thus the impact of SOG, SCROG, LST, defoliating, etc on "penetration".
Extinction coefficient (k) describes the attenuation of light density with vertical height. It depends strongly on the orientation of leaves. Planophile plants (most leaves are horizontal) have way lower K than erectophile plants (most leaves vertical). Especially when incident light comes from the zenit (the vertical).
The higher the LAI and k, the less light that reach the bottom areas.
In general, when using indoor just top lighting, it dont worth to have a LAI over 3. Usually a little over 2 is the max optimally useable indoors.
An ideal lighting must be designed according to LAI and k of plants being grown. And given the lighting setup is done, we must adapt LAI and k to the best values to get the best of the grow. Tyeing and pruning are great tools that allows us to strongly affect those parameters. Of course, LAI itself is very affected by how large is the plant, thus choosing the right vegetative time is critical to obtain the best results, as any mynimally experienced grower knows.
Therefore, its very difficult to generalize. What is good for 5ft plants probably isnt for 1ft ones. Different strains have different leaf angles, and more yet, plants have some ability to adapt it to the lighting environment. At the end, growers sharing their experience on their own conditions is the only key to improve on the long term.
There is no rules valid for all situations in this sense. Possible combinations of LAI and K are too many to fit a solution optimal for all. Aditionally, we can strongly affect them using growing techniques. Recently many people has discovered how defoliating plants may improve yields.
So we should forget to find an universal valid solution, but concentrate on understanding factors that affect on each situation and try to get the best for that concrete situation, either by manipulating the light setup, either by using general growing techniques.
But the main thing we must have in mind is that is not lighting that rules penetration, but plant's caracteristics.
Only understanding the given plant caracteristics we can design a lighting that works better for them. And on a opposite way, we can train our plants to use better a given lighting setup. Improvements on LED growing involve those two factors. Lighting and plants pattern must be considered together.
Estimating Absorbed Photosynthetic Radiation and Leaf Area Index from Spectral Reflectance in Wheat
G. Asrar, M. Fuchs, E. T. Kanemasu and J. L. Hatfield
Abstract
Some plant growth models require estimates of leaf area and absorbed radiation for simulating evapotranspiration and photosynthesis. Previous studies indicated that spectral reflectance, absorption of photosynthetically active radiation (PAR), and leaf area index (LAI) are interrelated. The objective of this study was to establish a procedure by which spectral reflectance can be used to simultaneously estimate PAR absorption and LAI. A method is presented for estimating the quantity of absorbed PAR by wheat (Triticum aestivum L.) plants and their LAI based on the normalized difference (ND), transformation of the near infrared (ρn = 800 to 1100 nm) and red (ρr = 600 to 700 nm) canopy reflectances. The results, from a theoretical analysis and field measurements, indicated that ND correlates with the fraction of PAR absorbed by wheat canopies. Bare soil reflectance and scattering of near infrared radiation by foliage elements were the major factors that influenced the relation between ND and PAR absorption. The estimated PAR absorption values, based on the ND, and four classes of assumed leaf angles (45°, 60°, 75°, and spherical), were used to indirectly evaluate LAI of wheat for three different geographical locations. The standard deviation on mean predicted to measured LAI's for the three locations varied from 0.5 to 0.9 for a range of 0 to 6 LAI. The method is considerably less sensitive in predicting LAI above 6.0 since the sensitivity of ND to changes in LAI becomes small (<0.01), due to small changes in canopy reflectance.
Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright ©
Main equations LINGRA
Yield formation
The “yield” results from the integration of daily (t) new formed dry matter allocated to “harvestable” organs:
Intersepted PAR
The quantity of new formed dry matter is dependent on the foliar interception and utilisation efficiency of incoming photosynthetically active radiation (estimated as 50% of global radiation:
Leaf area index
PAR interception is depending of existing leaf area index (LAI):
he value for extinction coefficient is taken from the C++ version of LINGRA used in CGMS.
Utilization efficiency
The maximum light utilisation efficiency of intercepted PAR in photosynthesis may be reduced by water stress (estimated by the ratio between actual and potential transpiration), temperatures below Tb2 value (crop and cultivar dependent) and it is also reduced by the high levels of PAR:
Leaf elongation
Initial, growth of leaf area after cutting is dependent on the number of tillers that after cutting have a node for leaf elongation. The average width of new leaves is a model parameter (i.e. 0.03 m) and the leaf elongation is described as a function of temperature:
Allocation
The partitioning of the newly formed assimilates is independent from weather the growth is sink or source limited and it is also influenced by water stress:
The two sources of assimilates are the carbohydrates previously stored, and the current photosynthesis. The actual crop growth is the minimum between assimilate demand and assimilate supply. When the assimilates produced by photosynthesis exceed the demand, the difference is stored in carbohydrate pool.
Actual leaves growth is derived from the amount of assimilates available for growth and the death rate of leaves by senescence which is enhanced by internal shading and water stress (Spitters and Schapendonk, 1990). Each tiller produces new leaves and in principle each axil of a leaf contains a bud to produce new tillers. The maximum number of tillers emerging from a bud is considered to be in average 0.69. Just after mowing this number is much less (0.335). This cascade of events is sensitive to light, temperature and stress conditions.
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-83582010000300001
INTRODUCTION
Light plays the most important role among all environmental factors affecting competition in mixed canopy (Keating & Carberry, 1983). Most of differences observed in the yield of competing species in mixed culture are due to differences in the amount of light received and/or its consumption efficiency (Sinoquet et al., 1996). Canopy structure is one important factor in determining the competitive ability of plants (Caldwell, 1987). The plant structure that is suitable for pure culture is not necessarily suitable for mixed culture. For example, although it is an advantage for a species in mixed culture, to have more leaf area index or more horizontal leaves above the canopy, it is not necessarily an advantage in pure culture (Rhodes & Stern, 1978).
Leaf angle, leaf area index, and leaf area distribution are traits with major role in light interception and consequently canopy photosynthesis (Anten & Hirose, 1999; Hirose et al., 1997).
However, those traits that lead to maximum canopy photosynthesis are not necessarily seen in each single plant. For example, photosynthetic capacity of canopy with vertical leaves is higher than horizontal leaves because more light will pass among the vertical leaves, reach lower layers, and lead to uniform distribution of light within the canopy. However, a crop with horizontal leaves will receive more light and have more photosynthesis when weeds have vertical leaves (Toller & Guice, 1996).
It is impossible to measure light interception by each species in the mixed canopy. So modeling of light interception process is considered as the most favorable method to determine the light received by any species (Berkowitz, 1988).
In the past decades, several models have been proposed to predict the competition for light. Photosynthetic models express how light interception and consumption is done by the different species in the canopy (Hikosaka et al., 1999). Spitters & Aerts (1983) proposed a model in which the canopy was divided into several layers, and light interception of each layer was calculated based on the contribution of leaf area to this layer. It is impossible to use light interception models in mixed canopy without describing the canopy structure and its effect on light interception by different species (Toller & Guice, 1996). To simulate the light received by species of broadleaf weed of Common cocklebur (Xanthium stramarium), this study was performed in competition with corn in order to determine the amount of light received as well as the affecting factors.
a propos przycinania liści.
Na własnej skórze odczułem skutki nadmiernej wycinki. Pod koniec wega zmniejszałem zagęszczenie w boxie, praktycznie wyciąłem ok 50% wiatraków, jednak to nie koniec w fazie flow ciachałem wiatraki, które dynamicznie rosły po przełączeniu na 12/12.
Efekt ? katastrofalny, zaburzyłem całkowicie fotosyntezę rośliny. Liści wiatrakowych zostało ok 20%, roślina nie mogła się pozbierać, kwiatostany były rzadkie jak kackupa. Co niektóre odrosty praktycznie nie rosły. Wniosek jest taki, że powierzchnia liści była za mała w stosunku do wielkości roślin. Dziewczyny nie odbierały wystarczającej ilości światła a za tym plon był fatalny średnio 24g z krzaka.
Trzeba mieć spore doświadczenie i wiedzę aby umiejętnie prowadzić wycinkę, która wspomoże kwitnienie.
Aktualnie lecę z kolejnym grow oczywiście też wycinam co nieco, wyczyściłem dolne odrosty i liście które nie rokowały jednak górę zostawiłem w spokoju. Jak narazie wszystko leci dobrze odległości po między partiami liści są małe co miejmy nadzieję da gęste i zbite topy.
Rośliny po wycince liści były bardzo wyciągnięte a odległości miedzy piętrami ogromne. Cały czas pilnowałem aby lampa nie była za wysoko. Jeśli któryś z odrostów wystrzelił za bardzo był łamany.
dzieki , starczy juz, juz weim wszystko,,, pozdrawiam
zawsze podcinalem ale po tym jak zrobilem glebszy resercz doszedlem do wniosku ze tym razem zrobie to jako jedyna forma treningu.
kompletnie pozbywaja sie lisci w pierwszym tygodniu kwitniecia
To nie może cała fotosynteza lecieć na przy topowych liściach?????
bo u mnie są tylko 3 liście wiatrakowe.