Germination and seedling growth under anaerobic conditions in Echinochloa crus‐galli (barnyard grass)^*

Abstract

Although rice has long been recognized to be uniquely adapted for growth in low oxygen environments of flooded rice fields, rice weeds of the Echinoehloa crus-galli complex appear to be at least as well specialized for germination and growth under such unusual biological conditions. Seeds of two varieties of E. erus-galli germinate and grow for prolonged periods in a totally oxygen-free environment. E. erus-galli germinates as well as rice {Oryza sativa) under a total nitrogen atmosphere and produces as large a seedling in spite of its much smaller seed size. Like rice, the seedlings of E. erus-galli are unpigmented, the primary leaves do not emerge from the coleoptile and no root growth occurs without oxygen. Of particular interest is the ultrastructure of mitochondria from anaerobically-grown seedlings. Mitochondrial profiles from the primary leaf of seedlings grown continuously in nitrogen are very similar to those grown aerobically. The size and shape of the mitochondria are similar and the cristae are numerous and normal in appearance. This is in sharp contrast to previous studies of other species which have reported that mitochondria were vesiculate and tended to lose their normal fine-structure after similar periods without oxygen.Finally, based on ultrastructure and ' "^C labeling studies, anaerobically-grown seedlings are highly active metabolically, which may explain, at least for E. erus-galli var. oryzieola, its ability to germinate and emerge from flooded rice fields.

Anaerobiosis in Echinochloa crus-galli (Barnyard Grass) Seedlings

“…Oryzicola is able to maintain a high ATP level with an energy charge of at least 0.8 in the absence of 02 (Rumpho, Kennedy, Pradet, unpublished data). However, in addition to energy, seeds germinated under anaerobic conditions require additional mechanisms to recycle pyridine nucleotides (both NAD and NADP), while carbon intermediates are essential for the biosynthesis of membranes and cellular components (10,19). Both the OPP pathway and tricarboxylic acid cycle may produce carbon intermediates, while the OPP pathway has been shown to provide the NADPH needed for lignin (14) and lipid (7) (19).…”

“…In the past, studies of anaerobic metabolism have concentrated mainly on the effects of flooding on plant roots with little attention directed toward germinating seeds (7). This is despite the evidence that most flood-tolerant plant roots are merely surviving temporary stress (4); whereas tolerant seeds, such as oryzicola and rice, actively metabolize under long periods of anaerobiosis (10,13, 17 …”

Germination of Echinochloa crus-galli (Barnyard Grass) Seeds under Anaerobic Conditions

“…Recently, we reported (13) In previous reports, we have presented information on the structural aspects of anaerobic germination in Echinochloa seeds (22), seedling characteristics and cellular ultrastructure (13), chloroplast ultrastructure (23), and metabolism of anaerobic germination (18)(19)(20). This paper presents information on the respiration and response to respiratory inhibitors of anaerobically grown Echinochloa seedlings.…”

A five year study of floristic succession in a restored urban wetland

“…It is conceivable that the seasonal waterlogged conditions in the Low Marshes precluded the establishment of many species that were flood intolerant. Only a handful of seed plant species are capable of anaerobic germination (Kennedy et al, 1980(Kennedy et al, , 1992. Recruitment for the Low Marsh from a smaller pool of wetland species would also be slower compared to that for the High Marsh, which had species introduction from a much larger adjacent pool of non-wetland species.…”