MRI of intact plants

Nuclear magnetic resonance imaging (MRI) is a non-destructive and non-invasive technique that can be used to acquire two- or even three-dimensional images of intact plants. The information within the images can be manipulated and used to study the dynamics of plant water relations and water transport in the stem, e.g., as a function of environmental (stress) conditions. Non-spatially resolved portable NMR is becoming available to study leaf water content and distribution of water in different (sub-cellular) compartments. These parameters directly relate to stomatal water conductance, CO2 uptake, and photosynthesis. MRI applied on plants is not a straight forward extension of the methods discussed for (bio)medical MRI. This educational review explains the basic physical principles of plant MRI, with a focus on the spatial resolution, factors that determine the spatial resolution, and its unique information for applications in plant water relations that directly relate to plant photosynthetic activity

Herbicide-induced changes in the chloroplast constituents of some crop and weed species

Changes induced by two herbicides diuron and atrazine in the chloroplast constituents of two susceptible crops (pisum sativum L. and pennisetum typhoides Stapf and Hubb) and two resistant weeds (Amaranthus viridiss L. and Cyperus rotundus L.) were studied. Considerable change in the levels of chloroplast constituents including chlorophyll, magnesium, and iron were observed in plants susceptible and resistant to herbicide treatment. The chloroplast nitrogen levels did not change much in resistant and susceptible plants either with diuron or atrazine. The chloroplast protein level showed an increase in resistant plants and a decrease in susceptible plants. The decreased protein level in chloroplasts was correlated with the decreased levels of total RNA of chloroplasts, whereas the chloroplast DNA was not correlated with the RNA levels of chloroplasts. From the present study, it appears that the chloroplast DNA may not have a direct role in determining the susceptibility or resistance of a plant to a given herbicide

Emergência e crescimento inicial de plantas de arroz e capim-arroz em função do nível de umidade no solo Initial emergence and growth of rice and Echinochloa sp. plants as a function of soil water level

Em anos de baixa precipitação durante o período pós-semeadura, as plantas de capim-arroz tendem a emergir primeiro que as de arroz, promovendo maior competição inicial com a cultura. O objetivo deste estudo foi avaliar o efeito do nível de umidade do solo, expresso em potenciais hídricos, no percentual e na velocidade de emergência, bem como no crescimento inicial de plantas de arroz e capim-arroz, em condições controladas. O experimento foi instalado em delineamento experimental de blocos casualizados, com quatro repetições. O solo utilizado foi Planossolo Hidromórfico eutrófico típico, para o qual foi previamente construída a curva de retenção de umidade. As unidades experimentais constaram de copos plásticos de 0,5 L, contendo exatamente 400 g de solo seco, e dos tratamentos dos seguintes potenciais hídricos (psiw): -0,03, -0,07, -0,1, -0,3 e -0,5 MPa, aos quais foram submetidas plantas de arroz e capim-arroz. Foi construída a curva de emergência para cada potencial hídrico e espécie; 20 dias após o início da emergência para cada espécie, três plantas de cada unidade experimental foram cortadas rente ao solo, sendo avaliados massa fresca e seca, conteúdo de água e emergência total. Plantas de capim-arroz foram mais eficientes na emergência sob potencial hídrico reduzido e menos eficientes no acúmulo de massa no início do desenvolvimento. As plantas não apresentaram estresse com potencial hídrico reduzido, e a faixa de umidade ótima para emergência do arroz foi mais estreita que para capim-arroz, situando-se ao redor de -0,07 MPa.<br>In lower than expected rainfall years during the early post-sowing stage, Echinochloa seeds tend to germinate and emerge before rice, increasing the competition along the rice development. The objective of this work was to evaluate the effects of water level in soil, expressed as water potentials, on the emergence level and speed, as well as early growth of rice and Echinochloa sp. plants, under controlled environmental conditions. The trial was conducted in a randomized block design with four replications. Lowland soil was used, for which a water retention curve was previously drawn. The experimental units were composed of plastic bottles filled with exactly 400 g of dry soil, and the treatments were water potentials (psiw) of -0.03, -0.07, -0.1, -0.3 and -0.5 MPa, where rice and Echinochloa plants were grown. The emergence curve was built for each water potential and species, and 20 days after emergence, three plants of each experimental unit were collected for water content, fresh and dry mass, and total emergence evaluations. Echinochloa plants showed better emergence levels under reduced water potentials than rice plants, but were less efficient in mass accumulation in the early days of development. Plants of both species did not show water stress under low water potentials, and the optimal water level in the soil was more specific for rice emergence, around -0.07 MPa