Seed vigor and initial growth of corn crop

Abstract

-Seed vigor is a characteristic that determines potential for fast and uniform seedling emergence and establishment of crops. Such characteristic defines crop initial growth what could have direct and indirect effects on capacity of plants in capturing natural nutritive resources and intervene in their competition intra-and interspecific. Aiming at identifying and understanding the possible effects of seed vigor on crop initial growth a field experiment was performed during two years at University of São Paulo, Piracicaba, SP, Brazil; using two seed lots at each year, which were previously characterized by tests of physiological potential as high and low vigor. Thus, five different ratios (100:0, 75:25, 50:50, 25:75, and 0:100) of seeds originating from seed lots with higher or lower vigor were used. Assessments were performed at the phenological stages of four and eight leaves by assessing plant height, stem diameter, and leaf area index. It was also observed that mean values for all variables assessed have increased according to increase of seeds with high vigor at planting row. Therefore, it is concluded that increased percentage of seeds with high vigor results in greater initial growth of cron crop until phenological stage of eight leaves.Index terms: competitive ability, physiological potential, weed competition, Zea mays.Vigor de sementes e crescimento inicial da cultura do milho RESUMO -Vigor é a característica que determina o potencial para rápida e uniforme emergência de plântulas e estabelecimento das culturas. Essa característica define crescimento inicial, o qual pode ter efeitos diretos e indiretos na capacidade da planta em capturar recursos naturais e intervir na sua competição intra e interespecífica. Objetivando identificar e entender os possíveis efeitos do vigor de sementes de milho no crescimento inicial da cultura, um experimento foi conduzido, por dois anos, na Universidade de São Paulo, Piracicaba, SP, Brasil; utilizando dois lotes de sementes a cada ano, os quais foram previamente caracterizados por testes de potencial fisiológico, como alto e baixo vigor. Assim, foram utilizados cinco diferentes proporções (100:0, 75:25, 50:50, 25:75 e 0:100) de sementes de lotes com maior ou menor vigor. As avaliações foram realizadas nos estádios fenológicos de quatro e oito folhas para altura de planta, diâmetro de colmo e índice de área foliar. Foi observado que os valores médios para todas as variáveis analisadas aumentaram de acordo com aumento de sementes com alto vigor na linha de semeadura. Assim, concluiu-se que o aumento da porcentagem de sementes com alto vigor resulta em maior crescimento inicial da cultura até o estádio fenológico de oito folhas.Termos para indexação: habilidade competitiva, matocompetição, potencial fisiológico, Zea mays.

Proline and trehalose in maize seeds germinating under low osmotic potentials

“…This hypothesis is supported by the knowledge that the response and tolerance of crop plants to abiotic stress are quantitative traits controlled by many different genes (Lopes et al, 2011). This fact reinforces the idea that different organs, or even different tissues of a same plant organ, may have distinct behavior regarding the degree of response to water stress (Abo-El- Kheir & Mekki, 2007;Mohammadkhani & Heidari, 2008;Anami et al, 2009, Tardieu, 2012. Therefore, specific study to better understand this phenomenon in the seed are matter of great interest.…”

“…The detrimental effect of water limitation on seedlings growth has been also observed by Mohammadkhani & Heidari (2008), and it was expected, shoot and root as because depend on the endosperm as source of energy, besides metabolites, until the plantlet achieves autonomy for its own support (Aoki et al, 2006).…”

“…The higher proline accumulation in the embryo axis, compared to that of endosperm, seems to be related to the greater metabolic activity and substantial presence of soluble carbohydrates in the embryo axis. This statement is based on the observations of Mohammadkhani & Heidari (2008), in which the accumulation of proline is relatively dependent on the levels of soluble carbohydrates in the tissues, since sucrose has a positive effect on the accumulation of this osmoprotectant. Although the endosperm of maize seeds is a storage organ, rich in carbohydrates, it is composed mainly of starch and other insoluble carbohydrates.…”

“…Although there are many studies regarding the strategies of plant drought tolerance, most part have focused mainly on parameters measured in the green tissues of plant shoots (Abo-El-Kheir & Mekki, 2007;Lopes et al, 2011). While there is no doubt that seed performance reflects on later plant development (Mondo et al, 2013), reports on the development of protective mechanism in seeds are still scarce in the literature (Thakur & Sharma, 2005;Mohammadkhani & Heidari, 2008;Špoljarević et al, 2011).…”

“…This mechanism is initiated by an osmotic adjustment to keep plant metabolism running, at least at a minimum rate, and for a relatively short period of time under drought (Mohammadkhani & Heidari, 2008). This phenomenon comprises the synthesis of certain compatible solutes that may have a prime role on the protection of key proteins, on stabilizing cell membranes, and on the control of instable chemicals species (Mohammadkhani & Heidari, 2008, Xoconostle-Cázarez et al, 2010. In this case, those compatible solutes are often designated as osmoprotectors.…”