Abnormalities in sweet pepper (Capsicum annuum L.) flowers and fruits induced by varying temperatures and irradiance

Jaafar, H. Z. (2006) Abnormalities in sweet pepper (Capsicum annuum L.) flowers and fruits induced by varying temperatures and irradiance. Journal of Tropical Plant Physiology, 1 (1). pp. 27-44.

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Abstract

Environmental factors, in particular temperature, when in combination with irradiance imposed a predominant impact on reproductive growth and development in many horticultural crops, which severity of expression is dependable upon the existence of varietal differences. The aim of the paper is to describe the morphological expressions of the flowers and fruits of two varieties of Capsicum annuum 1.. (Blue Star-BS, a tropical selection; Bell Boy-BB, a temperate selection) exposed to varying temperature regimes (14, 20, 26 ±3 DC) and irradiance levels (high, low irradiance). High irradiance of 3.8 MJ m-2 d-¹ supported normal flower growth, which subsequently developed into normal fruit when exposed to higher temperature regimes (20 and 26°C); whilst, low irradiance of 1.8 MJ m-² d-¹ did not seem to support sufficient biomass accumulation resulting in small, thin but still normal fruits. Low temperature at 14°C, however, retarded flower and fruit growth and development, which could not be compensated by the increased irradiance. The flowers and ultimate fruits produced were abnormal with both varieties exhibited similar susceptibility towards the low temperature impact. Malformation occurred at early flower stage displaying large, flattened ovaries, either singly or doubly, with increased number of carpelloid petals being formed. The stigma was thicker and longer, extending out of the closed petals that seemed to stick together, whilst the style was also thickened and pointed. The presence of stamens was not significant due to its stout statue. Some carpelloid-like bodies appeared from the base of the developing flowers, and grew into abnormal thin fruit-like, shrunken and flattened organs, with seedless or seed deficient ovaries, and blunt ends caused by the inhibited style elongation. The malformed fruits were flattened registering lighter weight than the nonnal fruits. Anthesis was hampered and only occurred about 60 days after the first bud appearance stage. At higher temperature regimes and light condition, BS appeared to respond better in its fruit growth and development (weights and size) compared to BB. implying a broader base line trait in the former, hence a better choice for greenhouse cultivation.

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