Nodule haustoria and microbial features of Cajanus and Pongamia parasitized by sandal (sandal wood)

Abstract

A field observation that roots of sandal wood tree (Santalum album (L.)) formed direct haustorial connections with root nodules of nodulating legumes was confirmed by pot culture studies on interaction between sandal wood plants and pigeonpea (Cajanus cajan (L.) Millsp.) or Pongamia glabra Vent. plants. The number of nodules and nitrogen content of plants decreased in parasitized nodulating species with corresponding increase in the nitrogen content of sandal plants. The root region of sandal had more of nitrogen-fixing bacteria and VAM fungi than those of pigeonpea.

Pongamia pinnata: An Untapped Resource for the Biofuels Industry of the Future

“…Among nine selected host species, including Wrightia tinctoria, Tectona grandis, Atrocarpus integrefolia, Swietenia mahogany, Azardirachta indica, Eucalyptus camaldulensis, and Acacia auriculiformis, P. pinnata together with Casuarina equisetifolia were shown in both pot and field trials to be the hosts capable of supporting the greatest biomass production of sandal timber [46]. In an earlier study Subbarao et al [74] demonstrated that in the case of P. pinnata and Cajanus cajan L., haustorial connections by S. album were not only with the root tissue of the host but also via direct contact to nodules. Not surprisingly, S. album haustoria connections with root nodules are established at the expense of the host plant in such aspects as nodule number and plant fresh weight.…”

Root hemiparasitism in a West African rainforest tree Okoubaka aubrevillei (Santalaceae)

“…Contact with hosts normally leads to a significant increase in growth in both herbaceous and woody hemiparasites, particularly if the host is a nitrogenfixing legume (Anantha Padmanabha, Nagaveni & Rai, 1988;Subbarao et al, 1990;Seel, Cooper & Press, 1993;. However, seedlings of O. aubrevillei were hardly larger, at 50 g d.wt, than the original seed mass of 43 g, even though the nitrogen-fixing host P. elata was strongly infected.…”

“…The degree of infection of host species differs (Rama Rao, 1918;Gibson & Watkinson, 1989). Nitrogen-fixing hosts in particular appear to be parasitized more heavily (Gibson & Watkinson, 1991) and haustoria directly attached to nitrogenfixing nodules have been observed in Santalum album (Subbarao et al, 1990). The degree to which root hemiparasites benefit in growth, photosynthesis and nutrient uptake from their attachment might depend on the nutrient status of the host so that attachment to nitrogen-fixing hosts may benefit the hemiparasite, particularly in nitrogen uptake and growth (Seel, Cooper & Press, 1993;.…”