Comparative Genomic Analysis of Rice with Contrasting Photosynthesis and Grain Production under Salt Stress.

Unfavourable environmental conditions, including soil salinity, lead to decreased rice (Oryza sativa L.) productivity, especially at the reproductive stage. In this study, we examined 30 rice varieties, which revealed significant differences in the photosynthetic performance responses under salt stress conditions during the reproductive stage, which ultimately affected yield components after recovery. In rice with a correlation between net photosynthetic rate (PN) and intercellular CO2 concentration (Ci) under salt stress, PN was found to be negatively correlated with filled grain number after recovery. Applying stringent criteria, we identified 130,317 SNPs and 15,396 InDels between two "high-yield rice" varieties and two "low-yield rice" varieties with contrasting photosynthesis and grain yield characteristics. A total of 2,089 genes containing high- and moderate-impact SNPs or InDels were evaluated by gene ontology (GO) enrichment analysis, resulting in over-represented terms in the apoptotic process and kinase activity. Among these genes, 262 were highly expressed in reproductive tissues, and most were annotated as receptor-like protein kinases. These findings highlight the importance of variations in signaling components in the genome and these loci can serve as potential genes in rice breeding to produce a variety with salt avoidance that leads to increased yield in saline soil

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

Seasonal changes and temperature acclimation of photosynthesis of rubber (<em>Hevea brasiliensis</em> Müll. Arg.)

Diplôme : Dr. d'Universit

Effect of temperature constraints on photosynthesis of rubber (Hevea brasiliensis)

The temperature responses of photosynthesis of two rubber clones, RRIM600 and PB260 were determined over a wide range from 10 to 45°C. Leaf photosynthesis measurements were performed at the Agriculture Faculty, Kasetsart University, Thailand and in a growth chamber at French National Institute for Agricultural Research (INRA-PIAF), Clermont-Ferrand, France. Photosynthetic rate of RRIM600 stayed almost constant between 23 to 37°C, and decreased distinctly with increasing temperature from 38 to 45°C. Photosynthetic rate of PB260 increased with increasing temperature from 10°C, and also decreased distinctly by lowering the temperature below 24°C or by increasing it above 36°C. These results indicated the similar shape of temperature response of photosynthesis of two rubber clones. (Résumé d'auteur

Photosynthetic capacity and temperature responses of photosynthesis of rubber trees ( Hevea brasiliensis Müll. Arg.) acclimate to changes in ambient temperatures

The aim of this study was to assess the temperature response of photosynthesis in rubber trees (Hevea brasiliensis Mull. Arg.) to provide data for process-based growth modeling, and to test whether photosynthetic capacity and temperature response of photosynthesis acclimates to changes in ambient temperature. Net CO2 assimilation rate (A) was measured in rubber saplings grown in a nursery or in growth chambers at 18 and 28A degrees C. The temperature response of A was measured from 9 to 45A degrees C and the data were fitted to an empirical model. Photosynthetic capacity (maximal carboxylation rate, V (cmax), and maximal light driven electron flux, J (max)) of plants acclimated to 18 and 28A degrees C were estimated by fitting a biochemical photosynthesis model to the CO2 response curves (A-C (i) curves) at six temperatures: 15, 22, 28, 32, 36 and 40A degrees C. The optimal temperature for A (T (opt)) was much lower in plants grown at 18A degrees C compared to 28A degrees C and nursery. Net CO2 assimilation rate at optimal temperature (A (opt)), V (cmax) and J (max) at a reference temperature of 25A degrees C (V (cmax25) and J (max25)) as well as activation energy of V (cmax) and J (max) (E (aV) and E (aJ)) decreased in individuals acclimated to 18A degrees C. The optimal temperature for V (cmax) and J (max) could not be clearly defined from our response curves, as they always were above 36A degrees C and not far from 40A degrees C. The ratio J (max25)/V (cmax25) was larger in plants acclimated to 18A degrees C. Less nitrogen was present and photosynthetic nitrogen use efficiency (V (cmax25)/N (a)) was smaller in leaves acclimated to 18A degrees C. These results indicate that rubber saplings acclimated their photosynthetic characteristics in response to growth temperature, and that higher temperatures resulted in an enhanced photosynthetic capacity in the leaves, as well as larger activation energy for photosynthesis