Studies on seed pathology and seedling diseases of some important indigenous tree species of kerala

In forestry, availability of healthy seeds is an important factor in raising planting stock. Initial seed health and storage conditions are the major factors governing the germinability of seeds. Like seeds of agricultural and horticultural crops, forest tree seeds are also liable to be affected by micro-organisms during storage, which affects the germination, and reduces the viability. Further introduction of seed-borne diseases into newly sown crops/areas on account of using unhealthy seeds is also not ruled out. Availability of healthy stock of seedlings is intrinsic for raising plantations and to meet this requirement elimination of nursery diseases by appropriate chemicals is of prime imortance. As exotic tree species may become susceptible to various native pathogens, it is generally considered better to select indigenous tree species for large scale plantations as they are well adapted to local environment. However, before taking up large scale afforestation progranme involving any indigenous tree species, it is essential to have knowledge about seed disorders and seedling diseases and their management. with a View to select appropriate tree species with fewer seed disorders and seedling disease problems for use in further plantation programme, four indigenous tree species such as Albizia odoratissima (L.f) Benth., Lagerstroemia microcazpa Wt., Pterocazpus marsupiwn Roxb. and Xylia xylocarpa (Roxb.) Taub. were evaluated to meet the above parameters

Environmentally compatible phyto-chemical larvicides for mosquito control

In the last decades considerable headway has been made in research and development of phyto-chemical pesticides. The most notable recent success is the commercial development of neem products for insect control. The present investigation on Environmentally Compatible Phyto-Chemical Larvicides for Mosquito Control was undertaken to identify plants of the locality with potential larvicidal activity on mosquito larvae. This has been achieved by screening 17 plant species against four mosquito species. The observation and data are compiled in six chapters .

Studies On The Effect Of Laser Radiation And Other Mutagens On Plants

The effect of lasers of three wavelengths in the visible region - 476, 488 and 514 nm on mitotic and meiotic cell divisions, growth, yield and activity of specific enzymes were studied in two taxonomically diverse plant species — A/lium cepa L. and Vicia faba. The effect of laser exposures was compared with the effect of two physical mutagens (Gamma and Ultraviolet radiations) and two chemical mutagens (Ethyl Methane Sulphonate and Hydroxyl amine). The study indicated that lasers could be mutagenic causing aberration in the mitotic and meiotic cell divisions while also producing changes in the growth and yield of the plants. Lasers of higher wavelengths 488 and 514 nm caused aberrations in the early stages of mitotic cell division whereas lasers of lower wavelengths (476 nm) caused more aberrations in the later stages of mitotic cell division. Laser exposure of 488 nm wavelength at power density 400 mW induced higher mitotic and meiotic aberrations and also induced higher pollen sterility than lasers of 476 and 514 nm. The frequency of mitotic aberrations induced by lasers was lesser than that caused by y-irradiation but comparable to that induced by EMS and HA. Lasers cause mutations in higher frequencies than UV. Lasers had a stimulatory effect on growth and yield in both plant species. This stimulatory effect of lasers on germination could not however be correlated to the activity of amylase and protease, the key enzymes in seed gennination. Enzymes such as peroxidase and catalase, involved in scavenging of free oxygen radicals often produced by irradiation, did not show increased activity in laser irradiated samples. Further studies are required for elucidating the exact mechanisms by which lasers cause mutations

Export trend of Indian ornamental fish industry

Inspite of having two hotspots of biodiversity India is way long back in the ornamental fish trade. Large number of species can only foster the needs of the industry. The study aims to (1) to find the various indigenous, exotic ornamental fish species and ornamental shrimp species being exported from India, (2) to provide an overview of the trends in the Indian ornamental fish export industry. 287 indigenous fish species, 92 exotic fish species and 44 ornamental shrimps have been found to get exported from India. The export trend of the industry for the past ten years shows a declining state which is also reflected in the annual and compound annual growth rate. Ornamental fish industry has enormous potential in tropical countries like India. To expand trade, new technologies and policies will have to be developed which will help in attaining a sustainable industry.

Induction of mitotic aberrations by Argon ion lasers in Vicia faba L. and Allium cepa L.

A comparat ive study of the effect oflaser in inducing chro mosomal aberrat ions at 4gg nm was done in View j aba L. (faba bean) and Allium ccpa L. (onion) with Argon ion laser (Spectra Physics Model 171). Seeds and bulbs of V.jaba and A. eepa were subjected to laser irra diation by 4gg nm excitations from Argon ion laser source at power levels 200 and 400 mW with power densities 2.25 mW em" and 4.49 mW em" and ditTerent exposure times (10, 20, 30 & 40 minutes). Similar to the effect of oth er physical and chemical mutagens, laser caused a dose dependent decrease in mitotic index and a rise in mitotic aberrations when compared to the control. In both plant species, mutations were observed in all stages of mitotic cell cycle. The total percentage of aberrations was two fold higher at 400 mW than at 200 mW exposure.