Seed dispersal of Diospyros virginiana in the past and the present: Evidence for a generalist evolutionary strategy

Several North American trees are hypothesized to have lost their co‐evolved seed disperser during the late‐Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon (Diospyros virginiana) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and coyote (Canis latrans), and two Pleistocene analogs; the Asian elephant (Elephas maximus) and alpaca (Vicugna pacos). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white‐tailed deer (Odocoileus virginianus)—a species not capable of dispersing persimmon seeds—comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human‐induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.     

Biochemical characterization of MI-ENG1, a family 5 endoglucanase secreted by the root-knot nematode Meloidogyne incognita.

A beta-1,4-endoglucanase named MI-ENG1, homologous to the family 5 glycoside hydrolases, was previously isolated from the plant parasitic root-knot nematode Meloidogyne incognita. We describe here the detection of the enzyme in the nematode homogenate and secretion and its complete biochemical characterization. This study is the first comparison of the enzymatic properties of an animal glycoside hydrolase with plant and microbial enzymes. MI-ENG1 shares many enzymatic properties with known endoglucanases from plants, free-living or rumen-associated microorganisms and phytopathogens. In spite of the presence of a cellulose-binding domain at the C-terminus, the ability of MI-ENG1 to bind cellulose could not be demonstrated, whatever the experimental conditions used. The biochemical characterization of the enzyme is a first step towards the understanding of the molecular events taking place during the plant-nematode interaction.     

Endogenous inhibitors and seasonal changes in abscisic acid in Dioscorea floribunda Mart. & Gal.

In the tubers of medicinal yam (Dioscorea floribunda Mart. & Gal.) abscisic acid (ABA) content was high in all the parts during the dormant condition in the winter, but it decreased to a very low level in the actively growing plants. ABA content of the entire tuber was negatively correlated with temperature and photoperiod. Growth inhibitors including batatasin-I and phthalic acid were identified in the dormant tuber.CIMAP Communication No. 673.     

Satellite DNA sequences as taxonomic markers in nematodes of agronomic interest

The success of alternative crop protection practices against plant-parasitic nematodes using host resistance genes depends fundamentally upon identification of the species and pathotypes effectively controlled by these genes. In the same way, biological control of insects by entomopathogenic nematodes will work only if the nematode strains used are indeed active against the pests to be eliminated. For these applications, the accurate interspecific and/or intraspecific identification of nematodes is thus of outstanding importance. Here, Eric Grenier, Philippe Castagnone-Sereno and Pierre Abad discuss the recent use of satellite DNA sequences in nematode taxonomic diagnostics.     

Organic acids and Fe deficiency: a review

Organic acid concentrations often increase with iron deficiency in different plant parts such as roots, leaves and stem exudates. The review summarises data available on the changes in the concentrations of organic anions in plants with iron deficiency and the effects of these changes in plant metabolism. The paper reviews data available in the literature on the changes in xylem and apoplasmic fluid composition with iron deficiency, both in plants grown in controlled conditions and in the field, and discusses the possible ways of iron complexation and transport in these compartments. The characteristics of the iron reduction and uptake by the iron-deficient leaf mesophyll cells are also discussed, with especial emphasis in the possible roles of organic acids in these processes. Both the possible causes and functions of the organic acid concentration increases in iron-deficient plants are reviewed.