Rubber Science

INFLUENCE OF STORAGE ON PROPERTIES OF NATURAL RUBBER LATEX CONCENTRATE AND VULCANIZATESResearch Articles
Pages 1 - 7
N. M. Claramma, L. Varghese & N. M. Mathew
- Abstract
- Keywords
High ammonia and low ammonia preserved centrifuged latices were stored for a period of 18 months. Effect of storage on properties of the latices and vulcanizates prepared therefrom was investigated. Mechanical stability time, zinc oxide viscosity, potassium hydroxide number and volatile fatty acid number were found to be affected by storage. Physical properties of vulcanizates were more or less unaffected by storage of latices .up to six months, but beyond this period, decrease in properties was observed. Ageing resistance of the vulcanizates was also found to be affected by the storage period of latices.

Natural rubber latex, Mechanical stability time, Zinc oxide viscosity, Potassium hydroxide number, Volatile fatty acid number, Latex vulcanizate, Ageing

DEVELOPMENTAL ANATOMY OF GERMINATING SEED OF HEVEAResearch Articles
Pages 8 - 12
D. Premakumari & P. Sobhana
- Abstract
- Keywords
Developmental aspects of germinating embryo of Hevea were studied with emphasis to the growth changes at the pre-emergence stage. The shoot pole of the mature embryo is a dome shaped meristem consisting of a unilayered protoderm, a hypodermal region, the procambium and ground meristem. Prolaticifer initials are distributed in all the three zones below the protoderm and in the cotyledons. The root pole is blunt and undifferentiated. Vascular differentiation is basipetal in the shoot axis starting with laticifer differentiation followed by sieve tube and xylem formation in the order. Primary laticifers are articulated and anastomosing. Root differentiation is irregular. Lateral root development advances before the initiation of tap root development.

Hevea, Embryo, Germination, Laticifer, Seed

POLYTHENE MULCHING IN RUBBER SEEDLING NURSERYResearch Articles
Pages 13 - 20
Radha Lakshmanan, K.I.Punnoose, M. Mathew, Jacob Mani & Jacob Pothen
- Abstract
- Keywords
The feasibility of using polythene films as mulch in rubber seedling nursery was investigated. Field studies were conducted with three types of clear polythene films, conventional plant mulch and an unmulched control. The polythene mulches were topped with a thin layer of soil of over 5 cm thickness . Mulching significantly enhanced seedling growth. Polythene-mulched plots recorded 15.5 to 28.9 per cent increase in plant diameter over the unmulched plots and compared favourably with plant mulch. The soil moisture content in the surface 0-15 cm soil layer with polythene mulching was 87-113 per cent more than that in the unmulched plots during extreme dry weather conditions, while the increase with plant mulching was only 50 per cent. The extent of weed control achieved with polythene mulching was 84 to 90 per cent and that with plant mulching 56.9 per cent, over the unmulched plots. Mulching with polythene sheets did not increase absolute soil temperature over the conventional plant mulches. Soil temperature fluctuations were also minimised due to mulching.

Rubber nursery, Mulching, Polythene film, Plant mulch, Soil temperature, Weed control

MANAGEMENT OF BLACK STRIPE DISEASE OF HEVEAResearch Articles
Pages 21 - 24
C. Kuruvilla Jacob, Thomson T. Edathil & Sabu P. Idicula
- Abstract
- Keywords
Field experiments were conducted to evolve a schedule for application of non-mercurial fungicides for protection of tapping panels of Hevea trees from black stripe disease caused by Phytophthora spp. Mancozeb 0.375 per cent and phosphorous acid 0.08 per cent gave effective and economic protection when applied at weekly intervals.

Hevea brasiliensis, Black stripe, Phytophthora, Chemical control

CHEMICAL MIXTURES FOR RUBBER WOOD TREATMENT BY DIFFUSION PROCESSResearch Articles
Pages 25 - 30
V.T.Jose, V.K.Rajalakshmy, K.Jayarathnam & C.R.Nehru
- Abstract
- Keywords
Experiments were conducted to find out an effective combination of chemicals for preservation of rubber wood by diffusion process. The preservatives tried included solutions of inorganic chemicals, organic chemicals and their various combinations. The results indicated that the combinations of borax, boric acid and sodium pentachlorophenate (NaPCP), phosphamidon and oxycarboxin, monocrotophos and oxycarboxin were the best against the sap stain fungus Botryodiplodia theobromae. The growth of Fusarium sp., Aspergillus sp., Trichoderma sp., and Penicillium sp. was significantly less in most of the treatments. Insect borers were effectively controlled by borax+ boric acid+ NaPCP, dimethoate + oxycarboxin, dimethoate + tridemorph and copper sulphate + borax.
Sodium pentachlorophenate proved to be an important adjuvant for the diffusion treatment of rubber wood though a few combinations devoid of NaPCP also showed encouraging results. The chemical combination of dimethoate and oxycarboxin can be considered an organic substitute in view of the toxicity of PCP compounds. Copper sulphate and its combinations with other chemicals gave good protection against insect borers but were effective against fungi only if NaPCP was added

Hevea brasiliensis, Wood preservation, Diffusion, Insect borers, Sapstain fungus

INCORPORATION OF 14C-ACETATE AND 14C-MEVALONATE INTO RUBBER IN STEM SLICES OF HEVEAResearch Articles
Pages 31 - 37
P. Seneviratne & A.W. Flegmann
- Abstract
- Keywords
For developing a procedure for early selection of high yielding Hevea clones, , experiments were carried out with stem pieces to measure the rate of incorporation of radioactive precursors ¹⁴C acetate and ¹⁴C-mevalonate into rubber. Uptake of acetate was found to be twice as high as that of mevalonate. Large variation was observed between the percentage ¹⁴C-acetate incorporated into rubber by stem sections from different individuals within the same clone, presumably due to stock- scion interaction. Mature stem pieces (resting stage of flush growth) were more efficient than young ones, the reason being attributable mainly to the differences in dry matter content. Ranking five clones by ¹⁴C-acetate incorporation put them into more or less the same order as ranking based on field rubber yield, with exceptions.

Hevea, Rubber biosynthesis, Early selection, Precursors