Dry-matter partitioning and radiation-use efficiency in cowpea cultivars (Vigna unguiculata (L.) Walp. cvs TC-9-6 and M-28-6-6) during consecutive seasonal courses in the Orinoco llanos

Abstract

SU MMARYField work on rainfed cowpea (Vigna unguiculata (L.) Walp. cvs TC-9-6 and M-28-6-6) was conducted in the Orinoco lowlands to explain the changes in dry-mass partitioning and radiation-use efficiency (RUE) as compared with other cultivars over four consecutive seasons. Growth features were assessed in early-maturing, prostrate-canopy (TC-9-6), and medium-maturing, erect-canopy (M-28-6-6) cowpeas. These cultivars were sown in consecutive middle-wet and late-wet seasons in double peak rainfall conditions. Dry mass accumulation by cultivars was assessed as a function of leaf-area duration and the efficiency with which radiation was converted into dry mass throughout the season (i.e. radiation-use efficiency). Cultivar differences in canopy architecture and duration of leaf area had a minor effect on the total dry mass production. In the early-maturing TC-9-6, RUE for a middle-wet and a late-wet season was 0 . 90¡0 . 04 and 0 . 65¡0 . 05 g/MJ, respectively. In the medium-maturing M-28-6-6, the values were 0 . 97¡0 . 05 and 0 . 72¡0 . 03 g/MJ, respectively. A season with rainfall below 100 mm had a negative effect on phenology and RUE. When average rainfall was above 100 mm, the total dry mass accumulation was not affected by differences in cultivars and seasons. The rate of harvest index (HI) changes was negatively related to pod-filling duration. The changes in assimilation distribution depended on the process of partitioning as modulated by the limited pod-sink and the photosynthate supply. However, the photosynthate source was not depressed by the sink activity of the pod-filling. Partitioning to non-reproductive sinks was maintained. M-28-6-6 with high dry-mass production and delayed senescence did not effectively divert a large amount of assimilate to pod-filling. Pod sink activity in cowpea was limited by genotype. Harvest index in M-28-6-6 decreased with the increasing dry mass. The final HI and rate of linear increase in HI differed between cultivars and were lower in M-28-6-6. The results of the present work in the Orinoco lowlands are relevant for a wide range of savannahs with a late wet season.

Impact of weather variables on drymatter accumulation and yield of mungbean [Vigna radiata (L.) Wilczek] varieties under different dates of sowing

“…It was observed that 25.4% of the total variance of pod and seed yield and 100% of the cause effect relationship were also explained by the first association (Fig 2). Absorption of PAR enhanced the drymatter accumulation as well as seed yield in soybean (Purcell et al, 2002;Ponte de Souza et al, 2009), maize (Lindquist et al, 2005), cowpea (San Jose et al, 2004) Results revealed that the variety Pant Mung-5 (V 1 ) may be adopted for sowing during first week of March (D 2 ) for better productivity because of its higher ability to absorb the PAR and PAR use efficiency than the other varieties and other dates of sowing tested.…”

“…The mungbean as a C 3s crop has a low potentiality for grain yield. In crops, determinants of drymatter production are the absorption of solar radiation by the canopy and the efficiency with which this radiation is utilized for biomass production i.e., radiation use efficiency (Montieth, 1977;Gallagher and Biscoe, 1978 ;San Jose et al, 2004, Zhou et al, 2011Nath et al, 2012). A number of factors are responsible to the variation of estimation of radiation use efficiency (RUE).…”