Comparison of the Uptake of Nitrate and Ammonium by Rice Seedlings

Abstract

The uptake of nitrate and ammonium by rice (Oryza sativa) seedlings was compared under various conditions. Nitrate uptake showed a 1-hour lag phase and then a rapid absorption phase, whereas ammonium uptake showed passive absorption during the first hour, then a shoulder of absorption, followed by a rapid metabolism-dependent absorption phase. Light did not affect the uptake of nitrate or ammonium. The uptake of nitrate and ammonium was markedly suppressed by removal of the endosperm. After removal of the endosperm, the uptake was restored by exogenous supply of 30 mm sucrose. No appreciable nitrate uptake was detected at temperatures below 15 C, whereas appreciable ammonium uptake occurred at 15 C, although lowered passive absorption and complete inhibition of the rapid metabolism-dependent absorption phase were observed at 5 C.Nitrate uptake was decreased by aeration and also by bubbling the mixture with O(2). It was greatly depressed by bubbling the mixture with N(2). These results suggest that there is a low optimal O(2) concentration for nitrate uptake. In contrast, ammonium uptake was increased by aeration, not influenced by bubbling with O(2), and slightly decreased by bubbling the mixture with N(2).Nitrate uptake was almost entirely inhibited by addition of cycloheximide, KCN, or arsenate. These compounds had scarcely any effect on the passive absorption of ammonium, but entirely depressed its successive metabolism-dependent absorption. Ammonium uptake occurred before nitrate uptake in solution containing both nitrate and ammonium.

Identification of arbuscular mycorrhiza-inducible Nitrate Transporter 1/Peptide Transporter Family (NPF) genes in rice

“…For optimal grain yield, paddy rice farming requires extensive watering (flooded by rivers and rainfall during the monsoon season, or by irrigation) for three quarters of the growing season, which influences the availability of the macronutrient nitrogen (N) in the soil. In non-aerated paddy fields, rice mobilizes ammonium (NH 4 + ) rather than nitrate (NO 3 − ) as the preferred N source (Fried et al 1965;Sasakawa and Yamamoto 1978). Yet, plant growth, yield and N-use efficiency are significantly enhanced when NH 4 + and NO 3 − are provided simultaneously (Kronzucker et al 1999;Kronzucker et al 2000;Duan et al 2007).…”

Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice: implications for rice cultivation and yield potential

“…It is therefore not surprising that NH % + nutrition, as opposed to NO $ − nutrition, has received almost exclusive attention in rice (Bonner, 1946 ;Fried et al, 1965 ;Shen, 1969 ;Wang et al, 1993). However, some reports have indicated that rice does possess some capacity for root NO $ − absorption (Ismunadji & Dijkshoorn, 1971 ;Sasakawa & Yamamoto, 1978 ;Youngdahl et al, 1982 ;Raman et al, 1995) and for the reduction of NO $ − in leaves (Tang & Wu, 1957). Isolated nursery trials have shown that NO $ − pretreatment of rice seedlings can result in enhanced transplanting success (Yamasaki & Seino, 1965), and, perhaps most strikingly, several varieties of Indica rice have been shown to exhibit superior growth on NO $ − under certain conditions (Ta & Ohira, 1981 ;.…”

【Short Report】Influence of the Improved System of Rice Intensification (SRI) on Rice Yield, Yield Components and Tillering Characteristics under Different Rice Establishment Methods

“…In the transplanting system, including manual transplanting and mechanical transplanting, rice seedling development is generally delayed due to injuries to the root caused by uprooting and replanting (Salam et al, 2001). Furthermore, the balance between water and transpiration in seedlings also changes, causing the leaves to wilt or partly die (Sasakawa and Yamamoto, 1978). Therefore, the growth and development of the seedlings become stagnant temporarily; this is the so-called "transplanting shock" (Sasakawa and Yamamoto, 1978;Salam et al, 2001).…”

“…Furthermore, the balance between water and transpiration in seedlings also changes, causing the leaves to wilt or partly die (Sasakawa and Yamamoto, 1978). Therefore, the growth and development of the seedlings become stagnant temporarily; this is the so-called "transplanting shock" (Sasakawa and Yamamoto, 1978;Salam et al, 2001). In the seeding broadcasting system, seedlings are grown in a nursery or plate, and at 15 − 20 days old, they are broadcast manually to the puddled field.…”