EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON VEGETATIVE AND REPRODUCTIVEGROWTH OF GROUNDNUT (ARACHIS-HYPOGAEA L.)

Effects of temperature x photoperiod interaction on vegetative and rep roductive growth were examined in three selected groundnut genotypes b y growing them in controlled-environment growth chambers with three te mperature regimes (22/18, 26/22, and 30/26 degrees C, day/night) under long (12 h, long day), and short (9 h, short day) photoperiods. The e ffect of photoperiod on the total dry-matter production (TDM) was sign ificant with the genotypes producing 32-72 % greater dry matter under LD than SD. Temperature x genotype interaction effects were significan t, with the dry-matter production being greatest at 26/22 degrees C an d least at 30/26 degrees C and 22/18 degrees C in two of the three gen otypes. Leaf area (LA) was greater under LD than SD at all temperature regimes. LA accounted for 76 % of the variation in shoot + root dry w eight (R-2 = 0.76, P < 0.01). A lack of relationship between LA and po d weight or pod numbers suggested that the pod development is controll ed by factors other than carbon assimilation. The temperature x photop eriod interaction was significant for root growth, with the root weigh t being maximal and photoperiod effects being minimal at 22/18 degrees C, while at 26/22 degrees C, root weight declined and photoperiod eff ects became prominent. Low temperature (22/18 degrees C) affected the reproductive development by reducing the proportion of reproductive no des in total (vegetative + reproductive) nodes. The conversion of pegs into pods, as indicated by pod to peg ratio (PPR), was lower in LD th an in SD conditions. Results suggested that the PPR could be used as a n indicator of genotypic sensitivity to photoperiod in groundnut.