Using the eddy covariance (EC) technique, flux of CO₂ and water vapour was continuously monitored for six years in a natural rubber plantation grown in central Kerala. The study period covered both immature and mature stages of the rubber trees (from 4th to 9th year of growth). The mean rate of CO2 sequestration during the entire study period was 9.2g CO₂ m^-2 day^-1, equivalent to 33.6 tons CO₂ ha^-1 yr^-1. These rates were largely in agreement with the results obtained through the biomass inventory method. The highest rate was seen when the trees were in 5^th to 7^th year of growth, possibly indicating that this was the peak growth

phase. As expected, it was evident that sequestration rates were the highest during those seasons of the year when sunlight was abundant and soil moisture was not deficient. 

The mean rate of water loss through evapo-transpiration of water was 3.2 mm day-1 and the ecosystem level mean water use efficiency (WUENEP) was 3.0g CO2 kg^-1 water. Implications of the high rate of CO₂ sequestration of rubber plantations are discussed in the context of mitigating climate change. Similarly, the relevance of high WUE of rubber trees is discussed in the context of expanding rubber cultivation to newer and non-traditional areas where annual rainfall is lower than in the traditional regions.

Yield data from eight clone evaluation trials, both small-scale and large-scale,were used for yield correlations in the early years with the overall yield. Irrespective of the trial, clones, years of planting and varying duration of yield recording, significant association was noticed between yield in the initial and later years. Yield of clones as early as in the third year in some trials and in the fourth year in all the trials showed strong association with the overall yield. Yield over the first four years of tapping and the BO-1 panel yield were significantly correlated with the overall yield. Yield in the third and the fourth years, entire BO-1 panel yield and the overall yield showed similar pattern in yield variations. Hence it is assumed that yield of clones in the fourth year of tapping is an indication of the overall yield performance of a clone. Thus it is possible that in a regularly tapped clone trial, even if the yield data recording is skipped or missed in the first couple of years, yield recorded in the third and the fourth years may be sufficient to identify clones for yield performance. Moving averages of the annual yields showed that the high yielding clones in the trials were top performing clones in the earlier years also, although there were annual variations. The study showed that promising high yielding clones can be identified from the fourth year of tapping.

Climate and landforms exert considerable influence on carbon (C) sequestration potential of agroecosystems. The carbon storage potential and nutrient availability in rubber plantations under different soil management units (SMUs) in three locations of Kerala namely, Thiruvananthapuram district in the southern region, Kottayam in the central region and Palakkad in the northern region were estimated. Significant variation in soil organic carbon (SOC) was observed between different locations, SMUs and SMUs under each location, whereas the variation in SOC stock between locations and SMUs within locations was not significant. An increasing trend in available potassium (K), calcium (Ca) and magnesium (Mg) in soils was observed from the southern to the northern district. Moderate to acute Ca deficiency was also noticed in the southern and central regions indicating the need for scientific intervention with respect to Ca nutrition of rubber plants. The study provided comprehensive estimates of the C sequestration potential of rubber plantations over a period of 25 years in different SMUs in various locations. Rubber plantations of the central region sequestered around 20 per cent more C than the northern region and 12 per cent more than the southern region. Among the SMUs, the C sequestration potential of rubber plantation was the lowest in SMU 5, 6 and 7. The study thus yielded valuable information for developing site-specific integrated C conservation strategies from a more sustainable and climate change perspective.

Somatic Embryogenesis Receptor Kinase (SERK) genes are known to express during the transition of somatic cells to embryogenic cells, which have the capability to differentiate into somatic embryos at a later stage of development. In the past 20 years, SERK have drawn much research interest due to its crucial role in somatic embryogenesis. The aim of the current study was to isolate and characterize HbSERK gene through cDNA cloning and to perform comparative genomic analysis. The partial cDNA sequence of HbSERK was 408 bp in length and comparison with genomic sequence revealed the presence of two exons separated by one intron. In silico analysis of HbSERK predicted a protein of 136 amino acids that revealed high similarity (99%) to amino acid of AtSERK1. Multiple sequence alignment showed that HbSERK possessed partial sequences from the characteristic intracellular kinase domain containing the subdomains from V-X of the SERK family. Molecular phylogeny of HbSERK with SERK from other plant species showed that HbSERK was clustered most closely with AtSERK1 and MtSERK1. 

Corynespora leaf fall disease (CLF) which is caused by Corynespora cassiicola is a serious leaf disease affecting rubber trees. The release of CLF resistant/tolerant clones for the industry is a challenge due to their long breeding and evaluation period. It is emphasized that precise identification of resistant clones at early stage of their breeding cycle is of utmost importance. The current study was carried out with the objective of screening Hevea genotypes based on growth performance and CLF disease severity. Thirty five genotypes belonging to the 2005 hand-pollinated progenies were subjected to screening along with their progenitors (RRIC 100 and RRIC 103, RRIC 52 and PB 86) and two check clones (RRISL 201 and RRISL 208). Experimental materials were multiplied by bud grafting. Field screening was done in budwood nursery and in the field at three locations viz. Nivithigalakale, Monaragala, and Gallewatta. Based on the dendogram derived by Power marker® software program version 3.25, genotypes were assessed according to grouping with tolerant clones RRIC 100 / PB 86, susceptible clones RRIC 103/RRIC 52, and moderately susceptible clone RRISL 201. Field screening results taken thrice were assessed along with control clones. Growth performances of selected genotypes were determined. It was found that HP 27, HP 30, HP 31, HP 45, HP 48, HP 51 and HP 61 genotypes which have performed well with respect to CLFD could be added to enrich the breeding pool.

Secondary phloem or bark, which is formed from the cambial tissue present in the peripheral side of woody plants, plays a pivotal role in the transport of photosynthetic assimilates and various other chemical molecules. In Hevea brasiliensis, the various cell components of bark include sieve tubes, companion cells and phloem parenchyma. The present study deals with the distribution and dimensional features of ray parenchyma in ten different clones of H. brasiliensis. The presence of ray was identified from soft bark region to the inner hard bark region and extended up to the outer hard bark region. The study illustrates three principal types of ray cells in the secondary phloem which are uniseriate, biseriate and multiseriate in nature. Among them, the proportion of multiseriate rays is far more when compared to uni and biseriate rays. Statistical analysis indicated significant variation among the clones for biseriate and multiseriate rays in soft bark and inner hard bark region. Significant clonal variation was observed for anatomical features such as height, width and height/width ratio of phloic rays. The variation was highly noticeable in the inner hard bark region. The characters which suggest significant clonal variation can be considered as prominent anatomical traits in breeding and exploitation strategies in Hevea clones. The study indicated that the frequency and dimensional features of phloem rays in the various zones of the secondary phloem were significant from the anatomical and structural perspective of the bark of Hevea.