Seasonal changes in resource allocation within an individual offspring of the wolf spider, Pardosa pseudoannulata (Araneae: Lycosidae)

Abstract.  Seasonal changes in resource investment into individual offspring are well documented, but no attention has been paid to the allocation of the invested resource among the body parts of the offspring. In the present study, seasonal changes in the absolute and relative sizes in a spiderling of the wolf spider Pardosa pseudoannulata Boes. et Str. are investigated, and the relationship between spiderling body size and the ability to moult during a food shortage is clarified. Spiderlings that emerge in November have a significantly larger cephalothorax and abdomen than those that emerge in June. In addition, the abdomen–cephalothorax size ratio is significantly greater in November than in June offspring. Under limited food availability conditions, only 40% of spiderlings moult. Nymphs that do moult have a significantly larger cephalothorax, abdomen and abdomen–cephalothorax size ratio than nymphs that do not moult. Thus, both the quantity of resources invested in the cephalothorax and abdomen of a spiderling and the proportional allocation of resources between the two body parts change seasonally in Pa. pseudoannulata ; alteration of the resource allocation occurs in late autumn. Larger spiderlings of Pa. pseudoannulata that emerge in late autumn would be able to develop into advanced instars even during food shortage, and therefore may have better overwintering survival rates.     

Reversal of ethylene action on cocklebur seed germination in relation to duration of pre-treatment soaking and temperature

Abstract At 23°C, both C₂H₄ and CO₂ stimulated the germination of freshly imbibed upper cocklebur (Xanthium pennsylvanicum Wallr.) seeds, but C₂H₄, unlike CO₂, changed to an inhibitor of germination under some soaking conditions. However, when seeds were pre-soaked for more than several hours at 23 °C prior to treatment, C₂H₄ strongly inhibited their germination at 33 °C, the degree of inhibition increasing with the duration of pre-soaking. Maximum inhibition occurred at 1–3 cm³ m^?3 C₂H₄ when seeds were pre-soaked for 1 week; further increases of C₂H₄ concentration and pre-soaking period decreased the inhibitory effect. C₂H₄ was synergistic with CO₂ when C₂H₄ promoted germination, whereas it was antagonistic when inhibitory. Such a transition of the C₂H₄ action occurred at ca. 27 °C. Also 1-andnocyclopropane-1-carboxylic acid, a C₂H₄ precursor, inhibited the germination of pre-soaked seeds at 33 °C, although it promoted the germination at 23 °C. When pre-soaked seeds were prepared for germination by chilling at 8 °C for 3 d, the inhibitory effect of C₂H₄ on the subsequent germination was manifested even at 23 °C. The reversal of the C₂H₄ action from promotion to inhibition in cocklebur seed germination is discussed in relation to the engagement of two respiratory pathways in the imbibed seeds.     

The Effect of Benzyladenine on Changes in Nuclease and Protease Activities in Intact Bean Leaves during Ageing

Primary leaves of intact bean plants (Phaseolus vulgaris L.) were treated with benzyladenine (BA) at different stages during growth. Changes in DNase, RNase, and proteas activities in the leaves were followed. Unlike the case of various excised tissues, cytokinin raised the activities of these hydrolases in intact bean leaves. Because BA elevated the levels of DNA, RNA, and protein in intact leaves, it may stimulate both synthesis and decomposition of these cellular constituents. The hydrolase activities showed differential responses to BA according to the age at which the leaf received the hormone treatment.