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Reproductive responses of cowpea (Vigna unguiculata(L.) Walp.) to heat stress. I. Responses to soil and day air temperatures

Authors
Journal
Field Crops Research
0378-4290
Publisher
Elsevier
Publication Date
Volume
8
Identifiers
DOI: 10.1016/0378-4290(84)90048-0

Abstract

Abstract Cowpea ( Vigna unguiculata (L.) Walp.) plants are characterized by occasional excessive abscission of reproductive organs which result in low numbers of pods per unit area and consequently low seed yields. The possibility that heat stress may cause this excessive abscission was examined. Interactive effects of different soil and two day air temperatures on growth and reproductive performance of cowpea cultivar ‘California Blackeye No. 5’ were determined in controlled environments. Emergence was slow, and the seedlings were stunted at constant soil temperatures equal to or lower than 23°C. Seedlings at 18°C soil temperature exhibited nitrogen deficiency, and they developed bigger and more numerous nodules on their roots. The different soil and air temperatures did not influence the duration from emergence to appearance of the first floral bud or to anthesis. The duration from anthesis to maturity of individual pods was six days longer with the cooler day air temperature, but it was not influenced by the different soil temperatures. Plants produced more pods at 27/19°C than at 33/19°C day/night air temperature; however, the variation in number of pods was associated with variation in the number of reproductive nodes per plant. Levels of flower abscission were not excessive in any of the environments, and plants at 33/19°C air temperature exhibited less percent flower abscission than plants at 27/19°C air temperature. The seeds produced at 33/19°C air temperature were misshapen. Normal and misshapen seeds exhibited high percent emergence when sown at a depth of 2.5 cm at all soil temperatures studied, whereas 5-cm sowing depth resulted in poor emergence at high soil temperatures with misshapen seeds exhibiting less percent emergence than normal seeds.

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