International Journal of Agricultural Policy and Research Vol.2 (12), pp. 421-443,December 2014 Available online at http://www.journalissues.org/IJAPR/ http://dx.doi.org/10.15739/IJAPR.015 © 2014 Journal Issues ISSN 2350-1561 Original Research Article Leaf water relation of four radish ( Raphanus sativus L. var. sativus) cultivars grown in controlled cabinets under varying temperatures and irrigation levels Accepted 4th November, 2014 Caser G. Abdel SG. Um IFGPAG, Leibniz Universität, Hannover, Germany. Author Email: caser.abdel@yahoo.com Tel.: +9647701610355 +4951776223481 Topsi, Famox F1, Corox F1 and Altox F1 radish cultivars were grown in controlled 20 and 12°C cabinets and they were subjected to 0, 33, 66 and 100% depletion of peat moss available water capacity (AWC). The objective of this experiment was to determine the performances of leaf growth and their water relations of four radish cultivars in response to varying temperatures and irrigation levels. The obtained results showed that radish grown in 20°C cabinet substantially exceeded that grown in 12°C in leaf saturation weight, leaf fresh weight, leaf dry weight by 7.39, 101.55 and 89.74%, respectively. On the other hand, 12°C grown radish highly exceeded that of 20°C in leaf water potential (6.44%). 0% AWC substantially bypassed that of 100%AWC depletion in terms of saturated and fresh weight of leaves, leaf water conductance and leaf water content by 144 and 141.1, 568.6 and 53.1%, respectively. 100% WAC depletion significantly exceeded that of 0% AWC depletion by 53.92, 53.79 and 238.4, 78.15%, in terms of leaf dry matter percentages, leaf water saturation deficits, leaf water potentials and leaf osmotic potentials. Cultivars performed better in terms of leaf growth at constant day: night ratio for 20°C than 12°C showing that performance might be better if there was thermoperiodism owing to alteration in cell growth rate. Cultivar performance under varying temperatures and water availabilities in term of leaf growth were categorized as Topsi> Famox F1> Altox F1> Corox F1. Key words: Radish, Raphanus sativus, temperature, irrigation, leaf water potential, leaf water conductance, leaf osmotic potential. INTRODUCTION Temperatures is one of the most potent growth limiting factors which usually acts over and below the optimal growth potential of a given species. Sirtautas et al. (2011) showed the different effect of low temperature and different photoperiods on photosynthetic pigments accumulation and chlorophyll ratio. After 4°C and 8 h (F1) and 4°C and 16 h (F2) treatments, photosynthetic pigments levels were lower in plants grown under 18/14°C and 8 h (F3) and 18/14°C and 16 h (F4) treatments. It indicates that radish leaves responded to low temperature by accumulating less chlorophyll a and b. They suggested that low temperature decreased photosynthetic pigments levels in shoots, but increased growth rate of roots. The combination of short day (F1) and low temperature treatment had the biggest influence on radish root growth. The opposite result was obtained under long day (F3) and 18°C temperature treatment. Krol et al., (1999) stated that exposure to low temperature inhibited chlorophyll a and b accumulation, and according to LWR, leaf weight and RGR, NAR measured their highest. The lowest chlorophyll content was found in F2 and the largest in F4 after both measurements. This suggests that the highest influence on chlorophyll accumulation was exerted by different temperature and photoperiod treatments.