Changes in the cellular content of three polyamines (putrescine, spermidine and spermine) were compared at different stages of development in zygotic and somatic embryos of Pinus radiata D. Don. During embryo development, both the zygotic and the somatic embryos showed a steady increase in spermidine content, with either a small decrease or no significant change in putrescine. This led to a several‐fold increase in spermidine/putrescine ratios during development of both types of embryos. Cell cultures of plant‐forming and non‐plant‐forming lines derived from the same clone and growing on proliferation (maintenance) medium differed significantly in their polyamine levels. Mature, cotyledonary stage somatic embryos capable of germination and formation of plants could be distinguished by their higher spermidine/putrescine ratios from abnormal cotyledonary stage somatic embryos which were incapable of forming plants.

A simple measurement of static contact angle of aqueous acetone droplets on surfaces has been developed for characterising leaf surfaces It allows leaves to be compared and grouped by their surface roughness factor and it differentiates between easy difficult and very difficulttowet species This paper describes how the method has been used to survey a large number of plant species including weeds and crops fruit and foliage High contact angles indicate difficulttowet surfaces The quantitative measure of contact angle is a useful tool to predict spray droplet adhesion and rank plant surfaces for retention properties It can also indicate whether surfactant addition is likely to be beneficial for agrochemical sprays targeted at fruit or foliage on different crops Surfactants were most useful for improving spray droplet adhesion and retention on difficulttowet surfaces but results varied with surface wettability surfactant type and concentration and with plant architecture

A model has been developed explaining 92 % of the variance in spray retention by individual plants. The effects of formulation and plant morphology were represented as a logistic function, because this can accommodate retention close to 100 or 0 % whereas an additive model cannot. All inputs for the current model, except for the plant morphology factor, Mp, could be readily measured. Mp could be estimated by a linear regression relating Mp to the leaf surface roughness, as determined by the contact angle of a droplet of 50 % acetone on the leaf surface. The use of a logistic function, and inclusion in the model of total plant area, plan area, and contact angle to account for plant morphology, has provided an improved, practical, easily used universal agricultural spray retention model needing few inputs.

Onion and potato crops require frequent applications of highvolume agrochemical sprays The use of two novel organosilicone adjuvant blends DuWett and Bond Xtra is being developed with the aim to halve conventional spray volumes on these crops Adjuvant use rates have been optimised through extensive studies of the physical characteristics of sprays These include leaf coverage retention foliar penetration and phytotoxicity Comparisons with conventional horticultural and other organosilicone adjuvants are made to illustrate the unique properties of DuWett and Bond Xtra which can improve the retention and coverage of sprays on onions and potatoes without increasing the risk of crop phytotoxicity

Sticker adjuvants enhance adhesion of pesticide sprays to plant surfaces and increase their resistance to rain This study evaluated the effect of two different sticker adjuvant types organosilicone/latex and terpene based polymers on the retention and rainfastness of a protectant fungicide tolyfluanid on Vicia faba (broad bean) and/or Brassica oleracea (cabbage) foliage On hardtowet cabbage the organosilicone/latex stickers provided better spray retention than the terpene polymers Increasing rates of the former resulted in increased retention of spray while use rate had no effect on terpene polymer performance After 4 mm rain (applied as a heavy rain event) up to 86 of fungicide deposits applied with organosilicone/ latex stickers were retained on cabbage In comparison