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Studies on the effect of climatic factors such as rainfall, relative humidity, temperature, sunshine hours, pan evaporation, evapotranspiration, solar radiation, vapour pressure and wind velocity on the button shedding, premature nut fall, and final nut yield of coconut, and crop-weather models developed to predict nut yield, are reviewed. The type of data and statistical analyses techniques used and the areas of research poorly addressed under the different topics are highlighted. Efectos de las condiciones climaticasy el liempo en el coco RESUMENSe revisan aquf los estudios sobre el efccto de los factores climaticos como las precipitaciones, la humedad rclaliva, la temperatura, las horas dc sol, la evaporacion de capas, la evapotranspiracion, la radiacion solar, la presion del vapor y la velocidad del viento en: la muda de los brotes, la caida prematura de los cocos y el rendimiento final del coco, y los modelos de cultivo-clima dcsarrollados para predccir el rendimiento del coco. Se han destacado el tipo de informacion y las tecnicas de analisis estadfstico utilizadas, ademas de los campos de investigation dentro de los distintos puntos tralados que se han abordado de modo poco eficaz.

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The numbers of pustules which subsequently developed on maize seedlings incubated at 5, 10, 15, and 20 OC and 100% r.h. were directly related to the temperature and length of incubation.The generation time was 16 days at 10 O C , 10 days at 15 "C, 7 days at 20 "C and 5 days at 25 "C. Increase in urediniospore production was observed with increase in temperature.Increase in the inoculum concentration up to 5 x lo4 urediniospores/ml increased the number of resultant uredinia. However, further increases did not increase uredinia-formation.

Germination of urediniospores of Puccinia sorghi on leaves and on agar was similar over the range 5-25 O C , being greatest at 15 O C . At this temperature, maximum germination was attained within 6 h. Germination on cover slips started at around 99% r.h. and increased with increase of humidity.Urediniospore germination was not affected by leaf age. In general, proportionally more spores germinated on the abaxial than on the adaxial surface. Maximum germination was observed on the abaxial surface of the tip portion of the leaf.The optimum temperature for infection structure formation was about 15 OC. A minimum period of 3-4 h was required for the initiation of infection. Increase in appressorium and sub-stomatal vesicle formation with increase in dew period was observed, with the maxima being attained at about 24 h after inoculation. I N T R O D U C T I O NAs a silage crop, maize is becoming popular with farmers in England. At present, Puccinia sorghi Schw. is not a major problem on maize crops in England, but, with the massive increase in maize cultivation, a severe outbreak cannot be ruled out.Little attention has been paid to P. sorghi in England. Reports of research work on some aspects of this fungus elsewhere in the world have been published in the past (Kushalappa & Hegde, 1971; Mederick & Sackston, 1972). Studies on the effect of temperature have been reported (Kushalappa & Hegde, 1971) but important aspects of biology and development have not been investigated fully and information is lacking on environmental and host factors. Therefore, the purpose of the work reported in this paper was to gather basic information on the growth of the fungus on maize under different environmental and host conditions. M A T E R I A L S A N D M E T H O D S Host cultureSeeds of the maize cultivar Kelvedon 33 were sown in soil-less compost in 11 cm pots and incubated in a glasshouse at 20-25 O C . After germination the pots were transferred to a glasshouse at 15-20 O C and a 16 h photoperiod with daylight supplemented by 400 w highpressure mercury vapour lamps. InoculumMaize leaves bearing uredinia of Puccinia sorghi were first collected from the plots of the National Institute of Agricultural Botany, Seale Hayne, Newton Abbot, Devon. A culture was developed from a single urediniospore as described by Mahindapala (1976). The culture was maintained by transfer of urediniospores, 4 wk after inoculation, to 3-wk old seedlings.