Effects of Temperature on Para rubber (Hevea brasiliensis Müell. Arg.) Leaf Photosynthesis Rates at Different Ambient CO2 Concentrations

บทคัดย่อ งานวิจัยนี้มีวัตถุประสงค์เพื่อศึกษาอิทธิพลของอุณหภูมิต่ออัตราการสังเคราะห์ด้วยแสงของใบยางพาราที่ความเข้มข้นของก๊าซคาร์บอนไดออกไซด์ต่างๆ โดยวัดการตอบสนองต่อความเข้มข้นของก๊าซคาร์บอนไดออกไซด์ของอัตราการสังเคราะห์ด้วยแสงสุทธิของใบที่อุณหภูมิต่างๆ ในห้องควบคุมอุณหภูมิ กำหนดความเข้มแสง 1,400 µmol m-2 s-1 ความชื้นสัมพัทธ์ระหว่าง 50-80 เปอร์เซ็นต์ ภายใต้อุณหภูมิ 9 ระดับ คือ 10, 15, 22, 28, 32, 36, 40, 42 และ 45 องศาเซลเซียส จากนั้นวิเคราะห์ข้อมูลการตอบสนองของอัตราการสังเคราะห์ด้วยแสงสุทธิต่ออุณหภูมิใบ โดยใช้สมการ 4th order polynomial equation และประเมินอุณหภูมิที่เหมาะสมต่ออัตราการสังเคราะห์ด้วยแสงสุทธิของใบที่ความเข้มข้นของก๊าซคาร์บอนไดออกไซด์ในระดับต่างๆ ผลการทดลองพบว่า สมการ 4th order polynomial equation อธิบายความแปรปรวนของการตอบสนองต่ออุณหภูมิของอัตราการสังเคราะห์ด้วยแสงสุทธิได้ดี การเปลี่ยนแปลงความเข้มข้นของก๊าซคาร์บอนไดออกไซด์ทำให้การตอบสนองต่ออุณหภูมิของอัตราการสังเคราะห์ด้วยแสงสุทธิของใบเปลี่ยนแปลงไป เมื่อความเข้มข้นของก๊าซคาร์บอนไดออกไซด์เพิ่มมากขึ้น อัตราการสังเคราะห์ด้วยแสงสุทธิจะเพิ่มมากขึ้น และพบการตอบสนองของอัตราการสังเคราะห์ด้วยแสงสุทธิต่ออุณหภูมิเพิ่มมากขึ้นด้วย และอุณหภูมิที่เหมาะสมกับค่าอัตราการสังเคราะห์ด้วยแสงสุทธิที่อุณหภูมิที่เหมาะสมนั้นๆ เพิ่มมากขึ้นเช่นเดียวกัน มีแนวโน้มที่จะอิ่มตัวที่ความเข้มข้นของก๊าซคาร์บอนไดออกไซด์มากกว่า 1,200 µmol mol-1 ABSTRACT   This research aimed to study the effects of temperature on Para rubber (Hevea brasiliensis Muell. Arg.) leaf photosynthesis rates at different ambient CO2 concentrations by measuring responses of the leaf net photosynthetic rates to the CO2 concentrations in the air at different temperatures in temperature controlled room.  The measurement was done using photosynthetically active photon flux at  1,400 µmol m-2 s-1, 50 % to 80 %  relative humidity,  and nine temperature levels; (10, 15, 22, 28, 32, 36, 40, 42 and 45 ºC). The responses of net photosynthetic rates to leaf temperatures were fitted using the 4th order polynomial equation. Then, the optimum temperatures for the net photosynthetic rate at different CO2 concentration levels were estimated. The result showed that 4th order polynomial equation provided good fit to the responses of the net photosynthetic rates to leaf temperatures. The changes in CO2 concentration influenced the responses. Increased CO2 concentration led to increased net photosynthetic rate and also the responsiveness of net photosynthetic rate to temperature. Finally, optimum temperature increased with CO2 concentration up to approximately 1200 µmol m-2 s-1

CoolBot Cold Room Monitoring Data Using Remote Sensor Designed by Kasetsart University

CoolBot Cold Room Monitoring Data Using Remote Sensor Designed by Kasetsart Universit

Investigations sur le rôle de la mobilisation des réserves et le partage des assimilats chez le jeune hêtre à l'ombre à l'aide d'une approche de modélisation intégrée

International audienceBeech (Fagus sylvatica L.) is a species of temperate broadleaved forests known to be very shade-tolerant. How does it manage to sustainably cope with very limited light resource? Processes must involve both C balance components (mainly photosynthesis vs. respiration) and efficient utilization/partitioning of the available C resource among the different sinks (mainly growth vs. reserve storage). We investigated them by combined experimental and integrated modelling approach

Waterlogging and restricted-below ground aeration on photosynthetic performance and root elongation rate of RRIM 600 and RRIT 251 rubber genotypes (Hevea brasiliensis Mull. Arg.)

Due to extended inundation, waterlogging and restricted below-ground aeration cause inhibition in plant growth performance. This study examined two different rubber clones, RRIM 600 and RRIT 251, for waterlogging and restricted below ground aeration. To evaluate the plant performance under the stress conditions, net photosynthetic rate (PN), maximum quantum yield photosystem II (Fv/Fm) and root elongation rate were observed. RRIM 600 has a higher photosynthetic performance under normal conditions. However, the PN rate and Fv/Fm ratio trend showed that RRIM 600 seems to have difficulties recovering after exposure to restricted-below ground aeration. Although RRIT 251 had a lower tendency of PN rate under normal conditions, the PN rate and Fv/Fm ratio of this clone showed fast recovery. RRIT 251 also performed a higher trend of root elongation rate under both stress conditions than RRIM 600

Investigating rules of reserve mobilization and assimilate partitioning in young shaded beech through integrative modelling

International audienc

A photographic gap fraction method for estimating leaf area of isolated trees: assessment with 3D digitized plants

A method for computing leaf area of isolated trees from perspective photographs was developed. The method is based on gap fraction inversion. Photographs are discretized into picture zones where gap fraction is computed from image processing. Canopy volume and leaf area density associated with each picture zone are computed from geometrical considerations and inversion of gap fraction equations. Total leaf area and the vertical profile of leaf area are computed from the product of associated volume and its density. The method has been implemented in software called Tree Analyser, written in C++. The method has been tested by comparison with direct estimation of leaf area of three-dimensional (3D) digitized trees of walnut, peach, mango, olive and rubber. Estimated leaf area was sensitive to picture discretization, individual leaf size and leaf inclination distribution. Optimal size of picture discretization was 17 times projected leaf size. Total leaf area was estimated by using a set of eight photographs taken around the tree in the main horizontal directions: deviation ranged from -11% in peach tree to +5% in rubber tree. The method allows fast and nondestructive monitoring of leaf area of individual tree canopies. The next version of the method will include the estimation of 3D leaf area distribution within the canopy

A photographic gap fraction method for estimating leaf area of isolated trees: assessment with 3D digitized plants

A method for computing leaf area of isolated trees from perspective photographs was developed. The method is based on gap fraction inversion. Photographs are discretized into picture zones where gap fraction is computed from image processing. Canopy volume and leaf area density associated with each picture zone are computed from geometrical considerations and inversion of gap fraction equations. Total leaf area and the vertical profile of leaf area are computed from the product of associated volume and its density. The method has been implemented in software called Tree Analyser, written in C++. The method has been tested by comparison with direct estimation of leaf area of three-dimensional (3D) digitized trees of walnut, peach, mango, olive and rubber. Estimated leaf area was sensitive to picture discretization, individual leaf size and leaf inclination distribution. Optimal size of picture discretization was 17 times projected leaf size. Total leaf area was estimated by using a set of eight photographs taken around the tree in the main horizontal directions: deviation ranged from -11% in peach tree to +5% in rubber tree. The method allows fast and nondestructive monitoring of leaf area of individual tree canopies. The next version of the method will include the estimation of 3D leaf area distribution within the canopy

Simulation of growth and development of beech seedlings growing in different light environments using PIAF-1.

International audienceThe European beech (Fagus silvatica L.) is a late-successional shade tolerant species. It is often cultivated and managed with the shelterwood system in Europe, meaning that its natural regeneration takes place in shade. Under low light conditions, seedling size must stay below a threshold where carbon gain and carbon balance remain positive. This is not so easy to determine experimentally. Therefore, a simulation approach using the carbon-based functional-structural model PIAF-1 (Lacointe and Donès, 2007) was used to investigate the relationship between carbon balance and growth of young beech trees under low light availability. Two-year-old beech seedlings were planted in March 2007 in the understorey of natural Scots pine stands in Fontfreyde, Chaîne des puys, France. In summer 2009, nine beech seedlings were sampled under light availability ranging from 7 to 28% of incident light. To acquire their architecture, aboveground parts of each tree were 3D-digitized, including woody parts (growth units) and leaves using PiafDigit (Donès et al., 2006). Then seedlings were harvested in autumn and winter to quantify biomass and starch and sucrose contents of each organ, above and below ground. Roots were separated into 3 classes: taproot, main lateral roots and fine roots. Each part was scanned and the length and diameter of roots were assessed using WinRhizo (Regent Instruments Inc., Canada). These data were used to parameterize and initialize PIAF-1. The digitized aboveground parts were converted from growth units to cylindrical segments bearing leaves in their true place and orientation. Belowground parts were reconstructed based on diameter and length of each root class. Meteorological data (hourly light and temperature) were generated for each tree based on recorded weather data. Transmitted solar irradiance above each seedling was calculated from hemispherical photographs and the global radiation above the stand. Each seedling was visualized on a PIAF-1 3D visualization interface. The quality of the reconstructed seedlings was assessed by comparing the graphical outputs from PIAF-1 with those from VegeSTAR (Adam et al., 2002) using Tree Analyser (Phattaralerphong et al., 2005) to compute synthetic geometrical properties such as total leaf area or density. Potential growth, amount of storage, and reserve capacity of stem, leaf and root are still being analyzed. Results of simulations will be reported and discussed