Environmental Factors Affecting Mushrooms 6z94w

Environmental Factors Affecting Mushrooms Light The reactions fungi to visible and UV light are of three main types : inductive, inhibitive and trophic (Cochrane, 1958). Inductive effects include both absolute light requirements of initiation or maturation of reproductive structures and quantities responses, such as increase in the number of reproductive structures upon illumination . Light is essential for the formation and maturation of reproductive structures in many species of wood rooting basidiomycetes (Kitamoto et al.,1972;Perkins and Gordon 1969). In addition the quality and quantity of light are important consideration in the formation and maturation processes (Eger, 1978) It is there fore important that the duration of light and its intensity are considered for individual species and, in the case of Pleurotus ostreatus, the line or strain within a species (Eger,1978). Lines of P.ostreatus have been shown to differ in their minimum and optimal requirements (Eger at el , 1974 ) The inhibitory effects of lights on fruit body initiation have been demonstrated for shiitake (Ishikawa,1967). In an experiment designed to determine the effect of light exposure during spawn run and fruit body initiation ,Ishikawo (1967) Exposed cultures to continuous light at 4 light intensities (50,100,500,1000, lux) For 5 exposure periods (0 , 10,30 ,60,80 days). He found an apparent interaction between light intensity and exposure period. For example, over 2.8 times as many mushrooms were produced by cultures exposed for 80 days to 1000 lux> Thus, exposure to light greater than 50 lux during spawn run may inhibit primordial formation . Unfortunately , Ishikawo (1967 ) did not provide statistical analysis of his data and it is , therefore impossible to determine the degree of variation associated with this observed interaction. Phototrophic response are common in fungi; an example is seen in Pleurotus species . positive phototropism in Pleurotus species was observed by Block et al .( 1959) and Gyurko (1972). A light intensity of 10 lux is sufficient to induce the response (Zadrazil,1978). San Antonio and Fordyce (1972) showed that at list 15 minutes of full sunlight were required for fruit body initiation of Volvariella volvacea; fruiting body initiation was not observed in any of their dark controls. Chang and Yau (1970) obtained fruiting under a 12 hr light: 12 hr dark cycle and under continual light an intensity of 500 lux was found to be optimum; the require for fruit body initiation was not photoperiodic . As a general rule, sufficient light for fruit initiation and maturation in most shiitake and P leurotus species is provided by “cool white” fluorescent bulbs for 2-4hr /day. Sufficient light is usually provided during normal picking hours.. LIGHT REQUIREMENTS FOR SOME EDIBLE FUNGI TYPES FUNGUS INDUCTIVE INDUCTIVE INHIBITORY INITIATION MATURATION A. BISPORUS NO NO NO F. VELUTIPES NO YES -------L. EDODES NO YES YES

TROPHIC NO ------NO

P. NAMEKO P. OESTREATUS V. VOLVACEA

YES YES

YES YES

-------------

------YES

NO

NO

NO

NO

Temperature Few generalizations can be made regarding temperature and vegetative growth and fruitification in edible fungi. Each species has its own optima for fruitification which may or may not coincide with the that of the vegetative growth. Of the 12 species with low and high temperature optima, A. bitorquis, F. velutipes, L. edodes, P. ostreatus, ,, P.florida and P.nameko have lower optima for fruitification temperatures ranges than that for the vegetative phases. If individual lines within a species with were considered, the number of species with lower optimum fruitification temperatures would increase considerably.. Thus, in general, optimum fruitification temperatures for most are lower than the optimum for the vegetative growth temperature. The optimum temperature for fruitification of a given species may be either close to the vegetative growth optimum, as in the V. volvacea and Tremella fuciformis, or considerably lower as in Flammulina velutipes, P.nameko and in some Pleurotus ostreatus lines. LOW AND HIGHTEMPERATURE OPTIMA OF SOME EDIBLE FUNGI . FUNGUS OPTIMUM RANGE OC REFERENCE VEGETATIVE FRUITIFICATION A. bitorquis 30 25 Vedder,1978 Auricularia spp 20-34 12-30 Cheng & Tu, 1978 F. velutipes 22-25 8-15 Kinugawa & Ffuruka, 1965 L .edodes 22-27 15-20 Ishikawa, 1967 P. nameko 24-26 5-20 Arita, 1978 P. eryngii 20-30 20-22 Cailleux, 1974 P. fabellatus 25-30 22-26 Bano , 1967 P. florida 30 25 Zadrzil, 1978, Rajarathnam & Bano P.sajor-caju 25-32 25 Jandaik Ksapoor, 1976 T.fuciformis 20-25 20-27 Chen & Hou, 1978 V. volvacea Morphological effects of temperature are easily observed , for example, the stipes of L.edodes and P. nameko may elongate and the pileus diameter may be reduced at temperatures above 16oC . In F. velutipes, production of fruit bodies at optimum

vegetative growth temperature 22-25oC RESULTS in smaller and slender mushrooms. The production of mushroom near their optimum temperature range should therefore contribute to a maximum quality product.. WATER RELATIONS Some fungi have specific substrate moisture optima that may depend , to some extent, on the type of substrate used. For example, a moisture content of 55-68 % is reported as being optimal for nutrient –supplemented sawdust used to produce L. edodes . In contrast , an optimum moisture content of 70% was reported by Akiyama , 1976 for spawn runoff L.edodes on natural logs. The optimum moisture content of traditional rice paddy straw substrate used to produce V.volvacea should be in the range of 6570% , while that of cotton waste substrate should be 70%.. For the production of shiitake mushroom, the optimum moisture content of both natural logs is critical for maximum mushroom production. For example, both natural log and synthetic log growers soak logs in water for 24-48hrs . Natural logs growers frequently soak the logs to induce the first flushes of mushrooms. On the other hand , synthetic log growers only soak only for the second and later flushes because sufficient water is present in the substrate to the first flush of mushrooms. Thus proper water management at the appropriate point in the crop cycle is crucial to the production of a high quality product. CARBON DIOXIDE The effect of CO2 the physiology of edible fungi may be substantial .The most widely investigated species is A. bisporus. The finding on the species may be related to other edible fungi.. Carbon dioxide levels as low as 0,1% may cause a delay in sporophore formation and reduction in sporophore initials in Agaricus. In shiitake restricting aeration by capping cultures with polypropylene membranes did not prevent the formation of buried primordial or exudation but reduced and delayed the number of primodia formed. Oxygen concentration above the colonies gradually decrease from 20.9%v/v over a 40 day period of incubation. It is assumed that carbon dioxide increases as the oxygen levels decreases , but since the carbon dioxide was not measured , it is difficult to estimate the threshold levels for primodia formation.. Other effects of elevated levels of carbon dioxide are on stipes elongation and pileus expansion. In Agaricus bisporus , there is increased stipe growth at carbon dioxide levels above 1% . In F.velutipes the pileus diameter decreases with increase in concentration of 0.06- 4.9%, stipe elongation is less sensitive to carbon dioxide than pileus expansion and both stipe elongation and pileus expansion are prevented by high concentration of carbon dioxide. Inhibitation of pileus growth by elevated carbon dioxide is limited to expansion phase of pileus development